Mastering Roof Inspections: Asphalt Composition Shingles, Part 14

by Kenton Shepard and Nick Gromicko, CMI®



The purpose of the series “Mastering Roof Inspections” is to teach home inspectors, as well as insurance and roofing professionals, how to recognize proper and improper conditions while inspecting steep-slope, residential roofs. This series covers roof framing, roofing materials, the attic, and the conditions that affect the roofing materials and components, including wind and hail. 


When you inspect an asphalt shingle roof, you don’t really have to determine the cause of a problem, but you do need to recognize that a problem exists and explain why the condition is a problem.

You’ll appear more professional if you can explain how serious the problem is, and you’ll want to be able to make proper recommendations. In order to do this, you have to have knowledge regarding the common causes of problems with asphalt shingles.  These problems can have many different sources. There may be no single cause; the problem may be the result of a combination of factors.

There are six common, general sources of problems. The first is installation.


To recognize installation problems, you need to understand the fundamentals of installation, along with the properties and limitations of typical roofing materials.

So many products and conditions exist that discussing them all lies beyond the scope of any roofing course. Most shingles have to be installed according to the manufacturer’s recommendations in order to perform as they were designed and for the manufacturer’s warranty to remain in effect.

As a home inspector, you won’t know what those manufacturer’s recommendations are, and you won’t be able to confirm compliance. Make sure your client understands that. Both your inspection report and the inspection agreement signed by your client should contain a disclaimer to that effect. If you fail to make your client aware of the limitations of your roof inspection, that oversight may come back to haunt you.

Installers sometimes assume that installation methods are the same for similar shingles made by different manufacturers. This is not always true, and this is a very important point:  Similar shingles made by different manufacturers can have very different installation requirements. It’s often impossible to know the proper installation method just by looking at the shingle.

During an inspection, you’ll be looking for typical installation methods. If you see something that looks different (and, obviously, if you see a failure), comment on it in your inspection report, but don’t call it a defect unless you know that it’s a defect. Pass on the liability by recommending further evaluation by a qualified roofing contractor or a roof consultant.

As already mentioned, installation problems often appear within the first few years after the roofing has been installed.  But remember that just because no one has noticed a leak doesn’t mean that the roof hasn’t been leaking.

Proper installation of asphalt shingles isn’t limited only to the manufacturer’s recommendations or even to the shingles. Shingles also depend on the proper installation of roof sheathing, underlayment and flashing. They all work together as a system.

What constitutes proper installation of these three components varies according to who manufactured them and what part of North America the home is located in.  The U.S. has radically different climate zones, and this is a situation where "one size does not fit all."

Installation may be affected by building codes, too.

Building Codes

The organization or entity with the legal authority to regulate roofing installation is the authority having jurisdiction (AHJ). Typically, the AHJ is the local building department.

Jurisdictions -- whether they're states, provinces, counties or cities -- are free to adopt whatever building codes they choose, or adopt only part of a building code, or adopt no building code at all.  AHJs typically defer to the manufacturers' recommendations concerning the installation of asphalt shingles.

A number of building codes exist.

The International Residential Code (IRC) is the building code most widely adopted in the U.S.  It is updated every three years, so there are different versions. Before the IRC came into common use, the Uniform Building Code was widely used.

Inspectors in Canada may need to refer to the National Building Code (NBC).

Homes are only required to comply with building codes which were in effect at the time of the home’s original construction, or when major work was performed. Homes are not required to be constantly upgraded to comply with newly enacted codes.  Remodel work that requires building permits should comply with the building codes in effect at the time the remodel work is done.

You should take the time to become familiar with the building codes that apply in your local service area. Regulations often vary from one jurisdiction to another. For example, you should know the maximum number of layers of existing roofing allowed to remain in place before all the roofing has to be torn off in order to re-roof.

Building codes have been developed over the years to protect the public, so they serve as useful guidelines for inspecting homes.  But a home inspection is not a code inspection. Your report and inspection contract should clearly state that your inspection is not a code inspection, but an inspection for safety issues, and system and component defects, and that it’s based on the InterNACHI Standards of Practice.

Quoting code in your inspection report may expose you to liability.  For example, in court, a plaintiff’s attorney may point out that, because you quoted code, you were performing a code inspection, so you were responsible for finding all code violations. If you are currently quoting code in your inspection reports, consider discussing that approach with your attorney.


Learn how to master a roof inspection from beginning to end by reading the entire InterNACHI series: Mastering Roof Inspections.

 Take InterNACHI’s free, online 
Roofing Inspection Course
Mastering Roof Inspections
Roofing Underlayment Types
Inspecting Underlayment on Roofs
Fall-Arrest Systems
Roofing (consumer-targeted)
More inspection articles like this