The Most Common Defect found in Home Inspections

You would be surprised at what home inspectors find most often.

By William Decker, CRI, CCI, CMI

When people think about home inspections, they usually think about the defects and problems the inspector will find.  They think about leaking roofs, crumbling foundations, leaking water pipes and furnaces that don't work.  Yes, we do see these type of defects, but the most common type of defect is one that the average home buyer would not believe and is almost always missed by municipal code inspectors.

The most common type of defect is improper installation by improperly or completely untrained tradesmen.

Home construction technology has been greatly increasing over the last decade, with new materials that are less expensive and provide a much longer service life.  But the problem with these new products is that the tradesmen who install them usually have not been trained how to properly install them.  People who have been working as roofers, plumbers or HVAC technicians for years, even those who were actually professionally trained for their trade (and most are not!) don't want to spend the time "going back to school".  And most jurisdictions do not have any requirements for the people doing the work to have actually been properly trained.

Today, there is little excuse for this.  The internet provides easy access to manufacturer's installation instructions.  Yet, again and again, inspectors find these defects and call them out.

High Efficiency Furnaces:  The new forced air furnaces achieve their 90% efficiency, in part, by getting their combustion air from outside the house.  For a furnace to create heat, the burners must have a source of combustion air.  Older furnaces took their air from the house, either with a draft hood (conventional furnace) or by an induced draft (mid-efficiency furnace).  This worked in older houses that were leaky, but with the new energy efficiency standards of insulation and air sealing, there is little or no excess air in the house to support combustion.

Improper Combustion Air Intake

As is seen in the picture to the left, the combustion air intake vent was not taken outside of the house.  This reduces the furnace's energy efficiency, shortens its life and is counter to the manufacturer's installation instructions.  Yet, this is how many HVAC technicians install these furnaces.  There is obviously a disconnect between how the manufacturer wants their product installed and how the installing technician understands.  This can also be seen in the way that many high efficiency furnace vents are installed.  High efficiency furnaces, being so highly efficient in the burning of natural gas, produce carbon dioxide, some carbon monoxide and water vapor.  Because of the large amount of moisture (and the relatively low temperature) of the combustion gas, it is vented outside using PVC tubing as opposed to the old galvanized pipe.  The exhaust (combustion gas) vent is supposed to be higher than the combustion air intake AND at least 3' from any window or door.  as you can see from the picture on the right, this is not always done.

Please remember that there is usually no training or qualification requirements for people to work as HVAC technicians.  Although there are schools that teach HVAC, most of the tradesmen I have come into contact with have only had on-the-job training.

Flat Roofs: I live in the Chicagoland area, so much of my work involves older masonry buildings, built between 1903 and 1935, with flat roofs.  The most common roof covering used today is modified bitumen (rubber roof) membrane.  The proper technique for installing the membrane on

Roof membrane with termination bar

the roof and securing the membrane to the side parapet walls with metal termination bar.  This bar holds the membrane in place and guards against leakage between the wall and the membrane.  It should be installed 12 - 18" above the roof surface (left).  Over time, the parapet wall deteriorates and the roof gets old.  Water starts to come out of the ceiling, below, and the homeowner hires a roofer to fix the leaks.  Remember, the roofer is NOT there to solve the homeowner's problem, the roofer is there to sell the homeowner a new roof.  The roofer sees the deteriorated brick on the inside of the parapet wall (right) and finds no place to properly attach the termination bar.  What to do?  The roofer does not want to tell the homeowner to hire a mason to re-build the wall before the roofer can put in a new roof because the roofer may lose the job.  What to do?

The roofer just takes the roof membrane up and over the top of the parapet wall (left).  Problem solved, right?  Wrong.  The roofer just covered the closed off the parapet wall coping ventilation.  Masonry walls with multiple wythes (layers) need to be ventilated at the top.  This allows moisture that enters the wall (masonry is porous) to evaporate in the spaces between the wythes and be ventilated out the top.  But the roofer has closed off this ventilation space.  What happens?

Moisture is trapped in the wall assembly and has no (easy) way to get out.  It can't evaporate out the top of the wall, as the building was designed to do, so it leeches out the sides, carrying with it some of the mineral salts that help to hold the mortar together.  This leakage can usually be seen on masonry walls in the spring (right).

Shingle Roof Installation: Recently, a local roofing company started advertising on the radio.  One of the major points that they stress in their ad is that they install their roofs according to the manufacturer's installation instructions, so that the homeowner's warranty is intact.  Gee, thanks alot.  Don't all roofers install the roof properly and give a warranty?  No, not really.

All new roof warranties are only the material warranty offered by the roof shingle manufacturer.  35 - 40 year shingles are warranted by the manufacturer, not by the roofer.  And this warranty assumes that the shingles are properly installed.  There are all kinds of requirements that the shingle manufacturer has for their product and if the roofer does not comply with all of them, your new roof is worthless.

One requirement is proper nailing.  The nails on each shingle have to be nailed at specific places on the shingle and the nail has to be properly nailed.  If the nails are not properly positioned or are improperly set, the shingle will rip and fly off.  With the introduction of more powered tools, more and more roofers are using powered nail guns to nail on roof shingles.  Unless the roofer is very careful, has a highly accurate nail gun and regularly adjusts it, the nail will be overdriven, under driven or crooked.  More convenient for the roofer, but there goes the shingle warranty.  Unless the shingles are hand nailed, it is impossible to determine if the nail is actually properly seated in wood.  With older roofs that have wooden plank roof decking, nail gun regularly drive the nail into the space between the planks and not into the wood.  There is no way for the roofer to "feel" if the nail gun has bit into wood or just space.  If not properly driven, the shingles are not properly secured and can just fly off.

There are other roofing considerations that many improperly trained roofers may ignore. Drip edges should be installed on both the eaves and the rakes of the roof.  The roof underlayment should be 30 lb felt and not the commonly uses 15 lb. Ice and water shield should be installed on all roof valleys, ridges, eaves and around roof penetrations.  At the eaves, the ice and water shield membrane should be installed 6' in from the exterior wall of the house, not from the edge of the eave.  There is a big difference between what is the minimally allowable standards for a roof installation and the best practices installation that will allow the roof to last for its full warranty period.  Roofers will commonly install new shingles over old shingles, explaining to the homeowner that it will be less expensive.  This practice is also allowed by most local building codes.  But, what is not explained is that when you install new shingles over old ones, the warranty is void and the life of the new shingles are cut about in half.  There are hundreds of details like this in any house.

In short, when having work done on your house, or when you are having a house built for you, it will really pay off for you to hire tradesmen who are fully educated and qualified to do the work.  Hiring a qualified, NARI certified contractor is one of the best ways to do this.  And hiring a certified home inspector look things over, during new home construction, is also a good idea.

How much training has your tradesman had?