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Crunchy numbers

A Boeing 747-400 passenger jet can hold 416 passengers. This blog was viewed about 3,500 times in 2010. That’s about 8 full 747s.

In 2010, there were 4 new posts, growing the total archive of this blog to 7 posts.

The busiest day of the year was November 17th with 34 views. The most popular post that day was Roofs Explained.

Where did they come from?

The top referring sites in 2010 were houseman.org, search.aol.com, statistics.bestproceed.com, mail.yahoo.com, and counter.bestproceed.com.

Some visitors came searching, mostly for skylight flashing, breaker box, electrical service, “main neutral” “utility neutral”, and roof types illustrations.

Attractions in 2010

These are the posts and pages that got the most views in 2010.

Roofs Explained January 2009
3 comments

Electrical Explained January 2009
6 comments

Explaining Foundations and Earthquake Retrofitting March 2010

About Jay Marlette December 2008

How Central Heating and AC works March 2010
2 comments

There are several ways a building is heated and cooled. Discussed here will be central air as it is the most typical way the condition air in residential construction. We will begin on describing central heat and then go on to explain how adding few components will turn the central heating system into an air cooling system. Heating and cooling the air is call air conditioning. However, the term “air conditioning” is often used when describing the cooling of a building.

Central air conditioning is the heating and cooling of air at a central location and the movement of that conditioned air into all the habitable portions of the building.
A central heating device is called a furnace. A furnace can be located in a closet, in the garage, in the attic, or in a sub area. Some homes have utility rooms for the soul purpose of housing the furnace and perhaps the water heater. A furnace contains a compartment where fuel is burned. Burning fuel in a compartment creates hot surfaces on walls of this compartment. When air is blown past this hot surface (the heat exchanger) the air is warmed. To keep everybody inside the house alive and safe from combustion gases, the compartment where the fuel is burned is vented to the exterior of the building and it never mixes with the air that is brought across the heat exchanger.

The most noticeable portion of the central heating and cooling system are the ducts. In a somewhat central location of the house a large vent in the floor, wall, or ceiling (the cold air return) will bring air from inside the building to the furnace or heat exchanger. Smaller ducts leading to each habitable room in the building will emit the air warmed by the heat exchanger. Conditioned air is handled by a fan that is installed in the ducting system (really old furnaces simply use the gravity of the heat). The furnace decides to turn on based on signals from the thermostat. The thermostat is set a temperature and when the ambient temperature falls below that setting, the furnace comes on.

Air cooling or air conditioning operates in a very similar manner. The only difference is that something cold has to live in the ducts so air can pass through it to become cool. The way this is done is a device called an evaporator is installed in the ducts. An evaporation is similar to the radiator in your car. A very cold liquid runs through this device and as air passes through it, it is chilled and delivered to the building. This cold liquid never leaves the system (in theory). The trick is to keep this liquid cool. This liquid is piped from a device that sits outside of the building and the soul purpose of this device is to cool the liquid. As air passes through the evaporator (inside the ducts) and the air is chilled, the liquid inside the evaporator looses its chill. It is then piped outside to the air conditioning unit to be re-cooled and then piped back to the evaporator. A thermostat set in the cool mode controls the air conditioning or cooling. When the ambient temperature exceeds the setting, the air conditioner comes on.

The following graphics shows the cooling concept. It also shows the condensate system. Basically, the evaporator in the ducts is really cold and drips like a frosty beer mug ( this a good time to take a break from this reading to pour yourself a beer). Welcome back. Notice how your beer mug is condensing on the outside and leaving moisture on your table. The mug isn’t dripping or cracked, just air around it is cooled and condensates. If we left this kind of moisture in the ducts, we would have a serious health risk. The evaporator has a drip pan below it that collects and drains the condensate (water) from the ducting system.

There are two basic types of foundations. First we have the raised foundation. This foundation consists of concrete (and sometimes brick) and is like a short wall that encircles the footprint of the building and acts as a base for the exterior load bearing walls. It is called a raised foundation because typically one can actually crawl beneath it. To prevent floors from sagging in the middle, there are usually one or more intermediate foundations that intersect the footprint of the building. The other kind of foundation is a slab foundation. The slab foundation is not nearly as interesting as a raised foundation. It is just a concrete pad for the whole building to sit on. Oh sure its not that simple as it has more reinforcement and thickness under load bearing walls but no attacking raccoons or deadly electrical fire hazards from field modifications. There are a few moisture vapor issues but that will be discussed at the end of this section.

The best way to describe a raised foundation is to build one verbally. In new construction concrete forms are made from wood form boards. Those are wood members that act as molds for the concrete pour and will determine the actual shape of the foundation. Once the foundation is poured, the wood form boards are pulled off. Form boards will not be shown in the illustrations. If one were to take a foundation and cut a cross section of it, it would like a thick upside down “T”. The wide part of the “T” is the footing and the vertical portion of the T is the stem wall. Without a thick footing the stem wall just cut into the soil like a knife. The footing reduces excess settlement. When looking at this cross cut one will even see evidence of reinforcement bar. These are steel bars about 20 feet in length connected end-to-end to each other to add more strength to the concrete along the stem walls and the footing.

This foundation is poured all around the perimeter of the building. To keep the middle of the floor diaphragm from sagging, we also install another middle foundation or a series piers along the middle of the building that support the floor. When piers are used, they typically consist of concrete footings, wood posts, and an “under the floor beam” that we like to call a girder.

After the foundation is poured and the form boards are removed, we place a piece of wood across the top of the foundation. This portion of the foundation is referred to at the mud sill. Embedded bolts, big square washers called sill plates, and nuts, bolt that piece of wood on to the foundation.

Once the sill plates are added, a cripple wall is built. This is a short section of wall between the foundation and the first floor that is built to assure a level floor diaphragm. Keep in mind, terrain where foundations are poured, are not necessary level. The cripple wall (sometimes referred to as a pony wall) gives one the chance to establish a level floor diaphragm despite the level of the terrain the foundation is poured upon.

From there the floors, walls, and roof framing are built and we have a house. Older homes with raised foundations often are not bolted or the bolts are small and less functional than ones in newer construction. In earthquake country foundations not only need to be bolted to the foundation, the cripple wall needs to be made stronger. Upon making the cripple wall stronger, this strengthened cripple wall must be well attached to the mudsill that is bolted and to the floor diaphragm it supports.

In the above graphic, the mudsill is bolted and have large square washers to prevent the sill from coming off by breaking round the bolt nut during an earthquake. The cripple wall that has been made stronger by nailing plywood to it is attached to the foundation with blocking. Wood blocks (typically two-by-fours) are nailed to the mudsill between the studs of the cripple wall so the plywood can later be nailed into the blocks. This creates a positive connection between the plywood strengthening and the mudsill. Above the strengthened cripple wall, the floor joists are attached to this system with connectors that are nailed into both the floor joists and the cripple wall. There are several ways to do this, in the graphic we are showing a Simpson-Tie® produce called an H-10 connector.

A slab foundation it typically a monolithic concrete pad that is steel reinforced. The concrete is thicker and deeper into the earth wherever a load bearing wall is going to rest upon that slab.

Notice the vapor retarder in the above graphic. Sometimes sand is placed over the vapor retarder so when the concrete is poured moisture from the cement can dry on both sides more evenly, which prevents the slab from curling or bowing. If you place a wet dish sponge on the kitchen counter, you’ll notice that when it dries it curls up a little. This is because the sponge is drying on one side faster than the other (which is the side resting on the counter). The problem with this method is that a reservoir of moisture is collected between the vapor retarder and the concrete slab and can result in moisture vapor passing through the floors. This could damage wood flooring placed on the slab. Better methods to prevent curling and moisture capture include using stronger rebar without the sand on top of the vapor retarder as well as better concrete water mix. If putting floors on a slab where it is unknown how it was constructed, consult a qualified flooring expert who knows about this issue and knows how to treat the slab surface before applying the floors.

There are three basic types plumbing in residential construction. Water supply, waste, and mechanical (gas or oil to appliances).

Let us start with water supply. Cold water first comes into the building from either the utility meter or well. When the water enters the building it reaches a fork in the road and some is piped into the water heater and the rest is piped directly to the cold side of fixtures, toilets, and hose bibs. Water entering the water heater is of course heated and delivered to the hot side of fixtures.

The water heater tank is filled with water. Beneath the tank is either a burner like that of a stove or inside the tank there are electric heating elements kind of like those seen inside an electric oven. There is a thermostat on the tank that either turns on the burner or the electric element when the water in the tank begins to cool.

Water heater tanks also have a number of safety devices. Keep in mind, a water heater is closed tank with a heat source. Did anybody say “Pipe bomb”? To prevent tank explosion a temperature pressure relief valve is present. This is a valve that releases the water and pressure through a discharge pipe (hopefully terminated in a safe location) when the tank improperly reaches a temperature of 210 degrees or the pressure exceeds 150 pounds per square inch the discharge pipe activates and releases the water.

There is one other type of water heater that is becoming more popular. This is the on-demand water heater. These are sometimes called the flash water heater. These are also called non-storage water heaters. These do not have a tank. Instead they are about the size of a suit case and are installed inside or outside of the building. Cold water enters this device and a computer sensor activates a burner (typically fueled by natural gas). This burner heats the water quickly and it leaves this device as hot water. This is a highly efficient as there is no tank to keep warm, but since there is an unlimited amount of hot water supply, water can easily be wasted by taking extra long showers.

Once the water is used, it’s going to have to leave the building sooner or later. That’s where the waste pipe comes in. Waste pipe is simply a pipe network that is bigger in size than the water supply pipe. It’s a larger pipe because by gravity, it carries both liquid and solid waste out to the sewer or septic system. All very simple but there is one more thing we need to know about waste pipe. Inside the waste pipe there are stinky and combustible gases. So what prevents stinky gases from the toilet from rising up and out of all the bathroom basins and sink drains? Enters the water trap. The water trap is a “U” shaped pipe that is seen underneath sinks and basins. Every drain barring the toilet has a water trap. The water spot in the toilet acts as a trap. The water trap holds a little water at all times to act as a seal to prevent gases from working their way up and out the drain. One more thing waste pipes have. Waste pipes are vented. Waste pipes connected to the waste pipe system that pass through the building and poke out through the roof. There are no covers because if rain water gets in, it’s simply sent into the sewer. Without vents in our waste pipe system water traps would siphon out (or suck dry) and waste would have more difficulty going down the pipe. Imagine you are playing with your straw while enjoying a soda. The vents is like taking your finger off the straw for the soda to drain out. If there is no air behind the waste, it would have difficulty making it to the sewer.

Mechanical plumbing is basically the pipe that brings fuel (typically gas or oil) from the gas meter or other fuel source to appliances such as the furnace, the water heater, the gas stove, the gas oven, and/or the gas dryer. The basics to mechanical plumbing is that gas runs through rigid pipe (usually black steel) and this pipe pokes out from a wall or floor behind or at a gas appliance. From there a gas valve should be established and a flexible gas connector should be established from this valve to the appliance.

In newer construction one may find corrugated stainless steel pipe, which is all flexible. It has yellow coating and should only be installed by one certified to install this system.

Branch Circuitry

The wires from the electrical panel to all the lights, plug receptacles, and other electrical devices are know as the branch circuitry. If the panel represents the trunk of a tree, the wires leading to all the electrical devices are the branch circuit wires. Branch circuit wires come in all shapes and sizes.

In older buildings, knob and tube wire is found. The wire type is named after the porcelain knobs and tubes used to attach this wiring to the building’s framing. The neutral and hot wires are spaced a few inches away from each other and strung throughout the building. This is the first widely used wiring that started phasing out of residential construction around the 1950s.

More modern types of wire used today are nonmetallic-sheathed cable (known as Romex®) and armored cable (known as BX®). Ungrounded versions of this cable became more prevalent in the 1950s. The neutral wire and hot wire are all wrapped together as cable and strung throughout the building. This cable has evolved (such as adding a ground wire) and still is used today. Nonmetallic-sheathed wiring belongs behind walls where folks cannot mechanically damage this vulnerable cable. Armored cable is allowed where it can be seen, like on a wall surface, because it is less vulnerable to mechanical damage. This cable is often seen on the wall surfaces of the garage where cosmetic issues are less important.

Along these branch circuits are junction boxes. Junction boxes are safe places for wire connections to live. Junction boxes can live along the cable where cables are attached to each other or at devices such as plug receptacles, switches, and lights. Junction boxes are made of both metal and plastic. Without junction boxes, arcs or sparks that can occur at these connections and pose a fire hazard. Junction boxes also reduce shock hazards as they make the wire connections less susceptible to mechanical damage and/or human contact.

The above photos are junction boxes. The box flush with the wall is missing a light fixture. The box in the crawlspace is missing a cover. Junction boxes must be covered.

The wires from the electrical panel (where the breakers and fuses live) eventually make it to electrical devices like lights, plug receptacles, and other electrical devices like dryers or attic fans. Understanding how devices work is best achieved by explaining how a plug receptacle works. Think of a plug receptacle as a face. This face has two eyes. Receptacles found in homes built from the 1960s on also have a mouth. Let’s start with the eyes. If you look closely you will notice one eye is smaller than the other. That smaller eye is attached to the hot wire. If you recall, the hot wire is the avenue of power from the utility company into the building. I best remember that the small eye as the hot by considering the monomer, “You’re hot so I’m winking at you!” The larger eye is the neutral wire. The neutral wire is the avenue of power back to the utility company. After your appliance, let’s say the blender, uses power, electrons are returned to the utility company via the neutral wire so they can sell this same power back to you later. Next we will talk about the mouth or the ground. If I ruled the world, I would probably change the name of that wire to “Secondary Neutral”. The ground wire is a second pathway from the receptacle all the way to the main panel where it reconnects to the neutral bar. The electrons then get back to the utility company through the neutral bar. Think of the electrons traveling through the wires as cattle. Good cattle stay in their corals. Naughty cattle, referred to as Mavericks leave their coral and pose a shock hazard. When Maverick electrons leave their hot-in/neutral-out coral they simply want to return to the ranch (utility company). If it can’t get to the utility company through the neutral wire, it will happily take another path. Suppose there is a blender and the wiring inside this device is damaged. The metal exterior case of the blender is charged. All it takes is one to touch the blender and simultaneously touch the kitchen faucet to get shocked. The kitchen faucet is grounded to the plumbing and that plumbing is grounded to the main panel (if the electrician grounded the building correctly). Unfortunately the heart is along that path so unless you have a defibrillator, ground your circuitry with a proper ground wire.

The GFCI (Ground Fault Circuit Interrupter)

One of the biggest safety improvements in electricity was the lightning rod. Ben Franklin showed the world that lighting could be safely diverted into the earth, which is the bases of grounding systems today. I believe that the Ground Fault Circuit Interrupter is a close second in terms of its simplicity and how well it saves lives. The concept is very simple, if electrons going to the blender from the hot side of the receptacle does not pass back through the neutral side of the receptacle, the GFCI shuts the receptacle down. You see, if the electrons are not returning to the neutral, then a person may be in the path of these electrons. In old homes, where ground wires are not available at receptacles, a GFCI provides a cheap way to make the receptacle safe without the expense of grounding. The National Electrical Code NEC allows for non-grounded existing receptacles be GFCI protected without having to establish a ground wire.

GFCI receptacles are typically required on all kitchen counter receptacles, bathroom receptacles, garage receptacles (except those dedicated to major appliances), and exterior outlet. Newer GFCI receptacles have a symbol of a padlock on the face of the receptacles. These GFCI receptacles have been improved to prevent corrosion and improper wiring.

Electrical Explained

By Jay Marlette

The Conceptual Electrical System

The problem with discussing how electrical systems work in a house, one needs to discuss Watts, Amps, and Voltage. These are nice concepts to understand but besides sizing how much service a building utilizes, several common defects discovered during a home inspection have very little to do with calculating wattage.

A Brief Explanation of Watts, Volts, and Amps

Let us start with the water analogy for electricity. Water goes down a pipe like electrons go down a wire. Both substances provide an ability to do work. Water coming out of the end of the pipe can turn a paddled wheel but probably not fast enough to get the blender to work very well and waterpower alone is difficult to use when making toast. So we turn to the power of electricity to do work. Each electrical appliance requires a certain amount of power measured in watts. Watts is a multiplication of amps and volts. What are amps and volts? Think of volts as the water pressure and amps as the water flow. So even if there is a lot of water pressure from the water source (Volts) you are only going to get so much water flow (Amps) out of your end of the pipe depending on the size of pipe. Just like water pipe sizing, you only get so many amps that can pass through a wire depending on the wire’s size and appliance load.

How Electricity is Used in a House

Power comes from the utility company and into a transformer. From the transformer power goes to the house. The wire or wires that bring power to the building are the “Hot” wires. Those electrons don’t stay in the building. Once the power is used, the electricity then goes through another wire from the house and back to the transformer. That wire is the “Neutral Wire”. From time to time you will hear about a ground wire. On three prong plug receptacles, this ground wire is connected to the lower third prong. This is a wire that hopefully leads an inactive life. This wire is there so if electrons escape from the house-to-utility company loop it will have some place to go. Maverick electrons are simply trying to return to the earth (or back to the main utility neutral via a separate wire). If we provide a an alternative path to the main neutral bare or more direct path to the earth perhaps people and electrical equipment will not get caught in the maverick electron stampede. Grounding the electrical system to the earth and grounding metal plumbing that could possibly be charged to the earth provides a degree of safety but also provides a path to the earth if the building is struck by lightning. Grounding also reduces noise on communication equipment.

Making Power Safe

Different types of appliances and fixtures require different loads. A load is the electrical demand of a piece of electrical equipment measured in amps and watts.

The way building electrical service works is power comes into the building (those overhead lines are the hots and neutrals). The power first goes through a meter so the utility companies know what to charge you, Those power lines are then connected to a breaker box that is attached to the house. Next, circuit breakers are plugged into this box. The breakers have switches on them and the ends of the switches have a number that represent how many amps may be ran through that circuit. Each breaker is like a thermometer that turns itself off if the circuit wire connected to it gets too hot. The breaker shuts down when the amount of heat passing through that breaker exceeds what is normal for that sized breaker. For example; a fifteen amp breaker (15 is the number at the end of the switch) will allow only enough power (or heat) to pass through it to allow for approximately fifteen amps worth of power. If significantly more heat than fifteen amps worth passes though the breaker, it will shut off. Fuses work the same way but instead of turning off, they burn out and need to be replaced like a light bulb.

Wiring sizing is important. The wires are sized by how much load we intend to pass through them. If we want to power lights we will install a 14 gauge wire in a 15 amp breaker to power the lights. 14 gauge wires are the thinnest wires we generally use in a building and they tend to serve smaller loads. If we want to power larger loads, like a dishwasher, we will use a 12 gauge wire on a 20 amp breaker. Wire gauge is a little confusing. The larger the number on the gauge rating, the smaller the wire.

Explaining 240 Volt Power

The concept of electricity does get a little confusing when discussing 240volt power. It is simple when explained. Remember those overhead wires entering the building? There are three. There are two hots with 120volts each and one neutral. One may ask, “…if we have two hots and we know the power returns to the transformer through the neutral wire, why don’t we have two neutral wires?” The answer is the two hots share the neutral wire when electrons return to the utility company. Then one may ask”…won’t the neutral wire burn up when both hots return the electricity through the one neutral wire?” The answer is yes if we were dealing with direct current but we are dealing with alternate current. Those two hots alternate when they pulse power to the building. In other words, those hots never constantly flow power into the building at the same time. At very high speed they dose the building with power in an on/off manner and never at the exact same moment. So the neutral wire that returns power to the utility company never gets a dose of power more than 120 volts at any one time. So one may ask, why do we have 240 volt power? Why don’t we just have 120 volt power? Well, we use to but now with electric stoves, electric water heaters, and electric dryers, the power could not get to the appliances fast enough to provide the heat energy necessary for these appliances to work.

Electrical Defects

Electrical defects can be found all over the building. This is why categorizing electrical defects can be difficult. Since this book is intentionally over-simplifying the house for an improved overall understanding of systems, we will give the electrical defects three categories; panel defects, circuit branch wiring defects, and those defects around fixtures, receptacles, and junction boxes. Defects described here will be those most common found in the author’s home inspection experience.

Panel Defects

Panel defects are found when the home inspector takes the panel cover off for a closer look. These defects include breaker configurations, wire sizing, labeling, wire connections, and grounding configuration. There are some breaker manufacturers with a bad reputation for not shutting down in time to prevent a building fire.

Starting with breaker issues, one of the most common defects found, even in brand new construction where permits were finalized, are multi-branch wiring defects. At this point, please keep in mind that even though permits were finalized, serious defects could exist. A professional home inspector, as opposed to a city inspector, not only has the luxury of time needed to thoroughly inspect a building, they also carry a lot more liability and tend to be more careful (This is an oversimplified statement. Let me mention here that among the building inspector crowd, I have met many dedicated inspectors who fight an uphill battle to improve building standards and their enforcement). A multi-branch defect is when a neutral wire is shared between two hots in an unsafe manner. Remember how we discussed how the main service wire (the wire you may see hanging over the street and connecting to the building) has two hots and one neutral? Sometimes to reduce the amount of wire installed throughout a building, two hot wires will share a neutral wire. This is commonly done when there is one breaker serving a dishwasher and another is serving a disposer. Since both appliances tend to be plugged into the same location, under the kitchen sink, then it makes since to have both those circuits share the same neutral wire. If one breaker is plugged into the breaker panel that is associated with a 120volt service wire, and the other breaker is plugged into the breaker panel at a point associated with the other 120volt service line, then the power alternates and the neutral wire shared never gets more than 120volts passing through it at a single moment and is safe. However, if the electrician goofs, and places both breakers on the part of the panel associated with the same 120volt service line (commonly referred to being on the same pole), then the neutral wire takes on too much power and can pose a building fire hazard. This is often corrected by reconfiguring the breakers in the panel so the neutral safely shared.

Another breaker defect is “Double Lugging”. This is when more than one wire is attached to a breaker. Some breakers are designed for this application but in most case double lugging creates an insufficient connection to the buildings circuitry and indicates insufficient breakers to service the building. The worst case scenario, double lugging could case an arc resulting in a fire.

Count wire-to-breaker connections from the top. The fifth connection from the top, two wires are inserted into the breaker. This is double lugging.

Some breakers need to be bridged or linked. When two 120volt wires are used on one appliance like an electric stove or dryer or when two circuits (a breaker and wire) enter the same junction box (like the junction box where the dishwasher and disposer plugs into) a bridge or link is required. A bridge or link simply forces two breakers that serve the same receptacle to go on or off at the same time. Here is the logic. An electric dryer is served by two 30amp breakers. Suppose one wants to change the plug receptacle serving the dryer to a more modern type. If one turns off the one 30amp breaker and the other does not shut off along with it, then the service provider will get shocked when he or she opens the junction box where the receptacle is replaced. The service provider falsely believes the power is out but there is a live wire from the other pole that was did not shut down.

The manufacturer of breaker could have an adverse effect on the building’s safety. Some breaker manufacturers are known to be prone to failure. Failure basically means that the breaker fails to shut down before the building catches on fire. The easiest manufacturer to pick on is the Federal Pacific Electric breaker. The Consumer Product Safety Commission published studies that support the idea that all Federal Pacific Panels should simply be replaced. Testing has supported that Federal Pacific Panels, especially the two pole breakers (240volt breakers) have a higher than average failure rate in terms of shutting down before a fire could occur. This study was conducted in 1982 in accordance to the Underwriter’s Laboratory standard 489. Some electricians serving FPE panels do not know that certain Federal Pacific Breakers do not fit in some FPE panels, one could inadvertently force a Federal Pacific breaker into a panel in a way that could cause a fire hazard without realizing it. The “Stab lok” Federal Pacific breaker design does not establish a solid connection in the panel as well as a modern panel. This could result in arcing and a fire hazard. Other manufacturers like Zinsco (also known as Sylvania because Sylvania bought Zinsco in the 1970s) and Bulldog’s Push-o-Matic have more field reports indicating that they may be defective but not as conclusively as Federal Pacific Electric. Most of these suspect panels were manufactured between the mid 1950s to the mid 1980s. That means regardless of the manufacturer, we are dealing with panels that are in excess of 20 years old. Breaker plasticides, springs, and other components have worn out. Breaker safety requirements have improved since these were manufactured, and these panels have been exposed to decades of environmental exposure. Simply due to old age, consideration should be made towards upgrading the panel.

To Be Continued … We will continue to discuss defects in the branch circuitry (House Wiring) and defects in junction boxes, receptacles, and so on.

The Conceptual Roof

Let us simplify the concept of roofing. They come in all different types, shapes, and sizes but no matter what kind of roof a building wears on its head, they all work in one of two ways depending on the slope of the roof. Before we explain slope, just remember this concept.

The more the roof slopes, the more like it works like series of umbrellas. The more the roof is flat, the more it works like a pond liner.

If a roof is sloped or has a pitch, it can use shingles. Shingles are like a bunch of umbrellas. They take a raindrop and let it drip to the next shingle until it eventually falls off the edge of the roof. If the roof is flat or has a low slope, the roof material needs to be more waterproof. The low slope roof should be able to hold pooling water as if it was covered by something as waterproof as a pond liner. The occupant becomes the bunny sleeping dry and cozy in her hutch underneath the pond. The amount of slope is determined by the Rise and Run.

Rise and Run

Pretend one is standing on top and at the edge of the roof (not recommended). That person begins to walk toward the ridge of the roof (the point at the top of the slope). If that person traveled 12 feet across and found herself 4 feet higher in the sky, she was walking on a 4/12 roof.

What is about to be said here may push your math teacher over the edge, but don’t reduce the fraction. We keep the denominator at twelve to keep things simple.

Umbrellas and Pond Liners

There are so many different types of roofs. Now that asphalt prices are skyrocketing (or going through the roof, get it!) several other types of roofs are appearing on the residential market like vinyl or PVC roofing. But we are going to keep it simple by discussing three very common examples of umbrellas and pond liners. First we will explain composition shingles as our umbrella, and second we will explain built-up asphalt gravel surface roofs as our pond liner. We will also discuss modified bitumen as another pond liner.

The anatomy of the modern composition shingle is a section of fiberglass fabric, impregnated with asphalt, and coated with mineral. The mineral is what makes the roof shingle surface feel like course sand paper. The mineral coating is like a strong sun lotion. This keeps the sun from chemically breaking down the asphalt material.

The roof surface must be prepared before installing these shingles. First there must be a flat surface. Plywood is sometimes installed on the roof if the original surface is not flat enough. Multiple layers of composition shingle is allowed by most building jurisdictions. This is not recommended because the composition shingles perform best on the flattest surface. Next, building paper is installed on this surface, and then the shingles.

The pond liner we will discuss is a built-up asphalt gravel surface roof (BUR). This roof is commonly referred to as a tar and gravel roof. This term is technically incorrect because these are built using asphalt, which is derivative of oil where tar is a derivative of coal.

A BUR roof is much like building one giant composition shingle over the entire building. First, there is a surface from which to start. Then building paper is applied and then asphalt is slathered on top of the building paper. This is done about three times (three layers or more) until it is time to apply the gravel. Just like the mineral on the composition shingle, the gravel is there to protect the asphalt from sun damage. Other sun blocks besides gravel are used such as roll composition, which is a mineral coated asphalt sheet applied over the built-up roof (referred to as a “glass cap”), or special paint designed to protect against sun damage.

There is one more pond liner worth mentioning because is it frequently uses as an alternative to a BUR. This material is modified bitumen. It is a roofing material that comes in a roll. The material is about 40 inches wide, rolled over the roof surface, and the seams are either torched together or bonded with a listed adhesive. That’s right torched. A gas torch softens the edges of this material and melts the seams together. Because of this method, this roof is often referred to as a “Torch Down” roof. Several jurisdictions are no longer allowing the torch method as it poses a fire hazard. The surface either is black (and should be painted), painted, or has mineral embedded into the surface very much like a composition shingles.

Flashing

Oh so vital! Flashing is how parts of the roof that are vulnerable to leaks are sealed or protected. Often, brand new roofs are installed but still leak because the flashing is not sufficient or correctly installed. Vulnerable areas include where things poke through the roof surface like chimneys, plumbing vents, gas appliance vents, roof edges, and changes in plane like roof-to-wall joints, roof valleys.

The discussion of flashing is focused on the shingled or umbrella type roof. This is because the flashing on a built-up roof are not generally seen. BUR flashing is integrated into the asphalt material.

We will over simplify roof flashing into two types, gooey flashing that comes from a can or caulking tube like mastic, and flashing fabricated from a solid and flat material like sheet metal. Mastic or other gooey flashings tend to be asphalt based. These are often used on repairs or and sometimes on new roof applications. Often, folks would rather send their children to college then to pay for better solid flashing. This stuff dries out every few years and needs to be re-applied. Sheet metal flashing is more reliable. Think of a piece of sheet metal flashing as a specially designed shingle (or umbrella) that both fits around a pipe protrusion and is properly placed within the shingles (or other umbrellas) to let the rain drop drip (or flash) over the other shingles.

Flashing comes in different sizes and shapes depending on what it is protecting. For example, flashing at a roof-to-wall joint or a skylight both utilize step flashing. Step flashing is just sheets of metal bent at a right angle and slipped between the counter flashing of the skylight or wall and also slipped under the shingles in a way that rain will flash off.

Edge flashing is just that. It consists of long pieces of sheet metal bent at an angle placed at the edge of the roof so rainwater does not damage the edges of the roof surface. On the drip edge of the roof this is placed under the building paper like an umbrella placed beneath another umbrella.

Roof Issues

Roofs leak and when they do, it’s an issue. The three main causes for roof leaks are; deteriorated roof material due to age, insufficient flashing, and improper installation. The latter is discussed because many are surprised when their new roofs leak. In most cases, the aforementioned roof types last approximately 20 years. Different types of shingle weights and products do last longer but 20 years is a rule of thumb.

Age

Composition roof deterioration is visible in a variety of ways. In some cases it is obvious. The shingles are crumbly (their asphalt substrate has dried out), they are cracked, or simply falling off. A more subtle form of deterioration is mineral wear. The sand like coating washes off, exposing the asphalt material. The sun does the rest of the damage until the roof needs replacement. Worn mineral means the roof is nearing the end of its life. Worn mineral and exposed fiberglass fibers mean it should be getting its affairs in order.

Built-up roofs, whether they are gravel surface, painted surface, or protected by a glass cap eventually wear. Deterioration is apparent at black spots where the sun protection has worn off (or maybe wasn’t originally applied) and the sun chemically broke down the asphalt-based material. Wear is also apparent when the roof surface has several cracks on the surface resembling alligator skin. This is where the term alligatoring comes from. These roofs are also nearing the end of their lives and it is up to the roofer to decide if they are willing to make repairs or only willing to replace the roof. Many roofers, understandably, do not want to be the last person on record to work on a roof that may leak. Roofers have been successfully sued when roofs leak, even if the leak occurred far from the area they repaired. Don’t let anybody say a roof only needs maintenance unless those words passed through a willing roofer’s lips.

Insufficient Flashing

Insufficient flashing can also fall into the category of “Improper Installation”. This topic gets its own section because it is a common cause of roof leaks. Improper flashing is similar to an umbrella being out of place. For example, a flashing component is placed over a plumbing vent but the up slope portion of the flashing is not tucked beneath a shingle. This is like having one of the umbrellas out of place and water flashed beneath this component and into the building. This incorrect application often occurs when new plumbing or a gas appliance is installed requiring a new vent. The installer will often incorrectly flash this vent.

Using mastic instead of solid flashing can result in leaks. This “flashing in a can” dries out every few years. The material cracks and each crack is an avenue for water to intrude into the building.

Missing counter flashing is another cause of leaks. Suppose a roof connects to an exterior wall. There is flashing under the shingles and this flashing sticks out and is placed against the siding. If that flashing is not tuck under the bottom of siding or a another piece of flashing that is seal against siding, then rain will drip down the exterior wall and seep behind the shingle’s flashing and seep into the building. This is like having a missing umbrella.

Edge flashing is often missing. This is a bent piece of sheet metal placed underneath the shingles along the edge of the roof. This flashing is necessary to prevent rain water from damaging the eaves through capillary action (capillary action is that stubborn rain water that doesn’t drip off the last umbrella (shingle) but works its way beneath it). Sometimes the edge flashing is installed incorrectly. The edge flashing at the drip edge of the roof belongs under the building paper. The edge flashing at the rake of the roof belongs over the building paper but under the shingles. Often the rake flashing is installed over the shingles, which is incorrect and drives rain water into the roof fascia causing decay.

Improper Installations

Remember the first thing to keep in mind?

The more the roof slopes, the more like it works like umbrellas. The more the roof is flat, the more it works like a pond liner.

Improper installation often is a condition that misses this fundamental idea. A common example is a shingled roof installed on a low-sloped surface. An umbrella is installed where a pond liner is needed.

A low-sloped shingled roof sometimes works for a while until something happens that causes water to pond on the roof. Leaves and other debris collect on roofs. On a low-sloped shingle system, a debris dam causes rain water to pool on the roof and this water seeps beneath these umbrellas.

Roof deck terrain also need to be considered when installing a pond liner like built-up roofing. If the roof surface has sags, which is not unusual on an older building, drainage considerations need to be made. Either a drainage scupper needs to be installed in the deep area or the roofing deck needs repair. Even though built-up roofs are waterproof, they are not designed to hold water for extended periods of time. On roofs with parapet walls (the exterior walls are higher than the roof surface) a secondary scupper should be installed incase the main drainage scupper is clogged. We don’t want water stored on the roof because it is very heavy and can cause structural damage.

In Conclusion

A qualified professional should inspect the roof for defects that are subtle but consequential. You don’t have to be a roofer to spot obvious defects. If you have a pair of binoculars, pitched roofs can quickly reveal defects. Even if the roof appears satisfactory or even new, get an inspection. Improper flashing details, incorrect use of materials, and incomplete work all lead to leaks in what appear to be pristine new roofs.

By

Jay Marlette

Home inspection is a relatively new industry that has evolved as American society changed. It would be safe to say that as society become more transient, tradespersons became more specialized, and building has become more complicated, the building generalist or home inspector was needed for the savvy home buyer. Understanding this evolution is important to the consumer because the professional home inspector is still being defined. Understanding this evolution helps the consumer appreciate what a home inspector does and to identify the most qualified home inspector.

People are often surprised to hear that home inspection is a new industry. Before World War II, when somebody bought a home, it was likely that his or her relative was a builder or trades person who lived a few blocks away and could check out the home. After World War II a few things happened. The G.I. Bill sent more folks off to college. With all these new degrees, families that lived in the same town or county started splitting off and venturing into new towns and cities to find the jobs that go with those degrees. That skilled relative was either no longer nearby or they were too busy building houses during the baby boom. As more people earned degrees, fewer people in the family were blue-collar workers. As fewer homebuyers were involved in the trades, fewer homeowners had experience in maintaining and repairing their homes. To make things more complicated, more building codes became implemented and tradespeople became more specialized to accurately follow the building code. As it become harder to find people who have general knowledge of all aspects of the house, a need for a generalist emerged.
The terms generalist and home inspector can be used interchangeably to help illustrate what a home inspector does. Home inspectors are generalists like a general medical practitioner. If a general practitioner sees inflammation in the throat, she recommends a nose and throat specialist. If the foundation has numerous cracks, a home inspector may suggest a qualified foundation expert to further evaluate its condition. Home inspectors are often confused with either building inspectors, who work for the city to make sure the new construction complies with standards, or contractors, who actually build the home.

Confusion between building inspectors, contractors, and home inspectors is understandable. The knowledge base in both of these trades is shared with home inspectors, and home inspectors originated from contractors. Understanding the differences in these trades helps us further understand how home inspectors evolved and who consumers should look to when seeking a home inspector. In order to differentiate between the trades, some attention should be given to describing building inspectors and contractors. Building inspectors safeguard the public from unsafe building practices by inspecting a home while it is being built. Building inspectors have been around for some time. As early as 1735 Benjamin Franklin started safeguarding the public with his calls for minimum standards in the design of fireplace hearths, hearth extensions, and combustible material clearance. Franklin made major contributions to each of the four main disciplines of building inspection: building, plumbing, mechanical, and electrical. Builders or contractors have been around a lot longer than that. I presume the builder came around when man first stepped out of the cave (or out of Eden). They actually build the house. Over time building has become codified through techniques passed down from one journeyman to the next or through secret guilds like the Mason Society. Masons were originally builders before they evolved into a clandestine secret society. Home inspectors have knowledge from both backgrounds in a more general sense. A home inspector should have knowledge of building code or she won’t readily identify when a home was built outside the standards of practice. She should be able to understand building practices that aren’t necessarily described in the building code. The home inspector should understand some code and building techniques but also why these standards are observed. This understanding is how the home inspector can determine if a safety concern is present. Remember, the home inspector is a generalist so she identifies the problem, explains the significance of this problem and refers it to the appropriate trade person. The home inspector essentially sees how well the contractor and/or builder constructed the home.

The need for home inspectors became even greater when building became complicated and craftsmanship suffered. Home building in America was predominately a craft. Though there were building standards throughout the 20th century, you didn’t just go to Home Depot and pick up a prefabricated window. You would open up your Audels Carpenters and Builders Guide (mine having copy rights of 1923, 1939 and reprinted in 1949) and open to page 1223 and figure out how to build a window from scratch. Though home building was a craft, there was simplicity to it. You only had so many electrical outlets, you may just have had one floor furnace for the whole house, and the framing was pretty straightforward. Now the skilled builder has been diminished with the availability of prefabricated building parts (with manufacturer installation manuals that are often ignored) that substitute for craftsmanship.

Requirements in the building disciplines have significantly increased to the point that few builders could specialize in all. Contractors often hire subcontractors to complete a portion of a building, such as the plumbing. The need for a home generalist or a home inspector has cometh. What separates a home inspector from a builder is that the builder must know building codes and building techniques. The home inspector must also have knowledge of these things as well as knowledge of common building mistakes. This person not only must know current building practices but old ones that require safety upgrades like old sliding glass doors without safety glass. Safety glass was not introduced into any building code until the 1960s. The contractor who installed sliding glass doors before and after 1964 would likely be the person with this general knowledge. Of course this would be just one tidbit of the vast body of knowledge the inspector needs to inspect a home.

The first home inspector was likely a contractor. It was unlikely the word “Home Inspector” that would be found in the Yellow Pages around the mid century. A good contractor with a general knowledge of the whole house was a good find. I would imagine at some point a contractor decided that they could just inspect homes for a living and quit swinging a hammer, an attractive prospect for a contractor reaching retirement. I would call this person the pre-modern inspector. This inspector may have been more thorough in areas that he or she worked in during his or her contracting days but less thorough in other areas. The pre-modern inspector is the one without standards of practice to go by to decide what to inspect and how to do it.

Because the pre-modern inspectors all had their own expertise, home inspections may have looked different from one inspector to the next. This must have been very confusing for the consumer. The home inspector who used to be a plumber may emphasize leaks where the home inspector that was a framer may emphasize joist spacing. It must have also been disconcerting to have the contractor/home inspector find defects in the home and offer to perform the repair service. A need for standards of practice and a code of ethics emerged. In 1976 the American Society of Home Inspectors was founded. Their objective has always been to build costumer awareness to the importance of a home inspection and to enhance the professionalism of home inspectors. This organization consists of members who elect to perform to ASHI standards and uphold their code of ethics. In some states, like California, where there are no licensing requirements for home inspectors, organizations like ASHI and CREIA (California Real Estate Inspector Association) provide some qualifying tests and continuing education requirements for the inspector. However, a California inspector does not have to join any of these groups and don’t require any kind of licensing. This is a scary situation for those who are putting their life savings into a home. Until licensing of home inspectors happens, the savvy home buyer can check to see if the inspector is an ASHI or CREIA member. It is my opinion that the emergence of creditable national associations and inspectors becoming specifically trained to be home inspectors represents the emergence of the modern inspector.

Understanding that home inspectors are in a separate discipline of training, we need to identify a modern and qualified home inspector. A contracting background is a plus. However, home inspectors are now becoming formally trained in home inspections. Now that some standards have been set, curriculum has been created to train individuals to identify defects and refer repairs to the appropriate trades. This training usually comes from one of three places: inspection firms who train their own, post secondary schools, and franchises. In all cases, well-trained home inspectors should spend time “riding along” with experienced home inspectors and, in my opinion, join a creditable home inspection association. At least by using home inspectors who join associations like ASHI or CREIA, you know the home inspector passed a thorough home inspection exam. With franchises, inspection schools, and professional inspection firms popping up all over the place, it is safe to say we are now dealing with the modern home inspector. Now if only we can say that with the modern home inspector appearing on the evolutionary chain that the consumer is safe when hiring a professional home inspector. The modern home inspector is still developing and there are some pitfalls.

Some business frameworks around the modern home inspector can potentially harm the consumer. Now that consumers are beginning to trust national home inspection associations, some new ones pop up that look official but do not require the same rigor to become a member. Without my knowledge, one “National Association” had me on their website as a member who passed their numerous exams which I hadn’t. With the emergence of associations that hand out meaningless credentials, consumers can be tricked into believing he or she is getting a qualified home inspector without checking the credentials of an association. It was suggested to me that I sign my dog up to become a member and find out how quickly he would be certified, but I decided not to disparage the reputation of my dog.

Another type of business framework that the consumer should be aware of is the franchise. Not seeking qualifications beyond the safe and familiar-sounding brand name of a franchise can be harmful to the consumer. Franchises for home inspectors are available for about $25,000. A person can buy a home inspection franchise without any background in home inspection or contracting. The franchise will train this person to inspect homes and effectively market his or her office. The franchise framework should have some scrutiny. There are many good franchise inspectors. Some franchises go through great efforts to provide their strategic partners with excellant educational opportunities. Some franchises are in the business of selling franchises, and less in raising the standard of care in home inspections. I rarely hear stories about franchisors handing back a franchisee their $25,000 dollars because they don’t seem to be made of the right stuff. Some franchises have referral agreements with other types of services like alarm systems. It is unethical for a home inspector to sell client information or to recommend other services for a fee. Some real estate offices have preferred vender programs. Most home inspectors know that their main source of business referrals come from real estate agents. That is okay if the inspector is being referred because of his or her competent inspections and honesty. Some preferred vender programs require the home inspector to pay to be on that list. ASHI has taken a stand that this violates their code of ethics because paying for a referral is harmful to the consumer. And here we are. The modern inspector stands before you and is still evolving. It will be interesting to see which type of modern inspector the market will Darwin out.

The reason it is important to understand the evolution of the home inspector is that the organizational and business framework around the modern inspector is very dangerous to the consumer. Now with safe looking brand names in front of modern inspectors and official sounding organizations, the consumer is truly challenged to decipher where the qualified inspector resides. In California an ASHI or CREIA inspector is the way to go. A person can go to a franchisee’s website and see that “premium inspectors” reside within that network. General contractors may call themselves home inspectors with the sole purpose of garnishing work. Seeking an inspector requires more scrutiny than ever before.