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A Home Inspection in Nassau NY: Multiple Roof Layers | 4 Things to Consider when adding a roof layer

Today I performed a home inspection in Nassau NY. As I was performing the home inspection, I made note of the roof containing multiple layers. Most roofing contractors in upstate NY and Nassau NY usually are not fans of a "nail over roof". A "nail over" roof is a home inspection term used to describe a roof installed OVER an older roof. Usually, it is an asphalt roof over another asphalt roof. When we are performing a home inspection on a structure that contains 2 layers of roofs, we really want to make sure we have a good look at the shingles, flashing and crawl the attic to check the underlayment/decking. Reason being, we really have to see if there are any adverse effects happening prematurely during the home inspection due to the additional layer of roof.

I found the picture above online. This is not the roof from our Nassau NY home inspection. Although the picture above reflects a multiple layer roof severely distorted, this is not always the case.

Our client was concerned if the roof was going to hold up which is a legit concern when discovering multiple layers of roof. My home inspector trainee and I thoroughly inspected the roof from the outside looking for signs of premature failure such as curling of the shingles, bulging and or bubbling of the shingles and or other abnormalities we could see during the home inspection. Overall, the roof nail over appeared to be about 10 years old, the shingles were secure, even and totally flat. We inspected the flashing around the chimney and skylights, and they appeared to be installed properly, flush and did not appear to be leaking during the home inspection. My home inspector trainee assisted me with inspecting the underlayment. There were no visible signs of staining, wood rot and or mold which would have indicated to us of small previous leaks from the original roof, long term roofing leaks which would have been evident of wood rot and or poor ventilation.

Above diagram reflects where flashing may be present.

Thankfully, the roof was 1 story high, walkable and the attic was fully accessible and visible. Sometimes this is not always the case.

The home inspection we performed in Nassau NY led me to write the article below:

4 Thing to consider when purchasing a "nail over" roof.

How Many Layers of Shingles can be on a roof?

In most areas of the country, local jurisdictions only allow 2 layers of shingles on a roof due to fire safety and quality control. If you are allowed 2 layers of shingles – why do, we see 3,4 and 5 layers on some homes?

When a roof has 2 layers and you are looking to correct a roof issue, a home inspector or roofer may recommend a full replacement. Although a full replacement is always recommended, if you are on a tight budget and have 1 roof layer you may be able to install a nail over roof. Although not recommended.

In order to have a nail over roof your current roof cannot be distorted and or damaged. The roof you are looking to have a nail over done on cannot be buckling, peeling and or potato chipping. The roof should be at the end of its life and be free of physical defects such as cracks and or bumps.

Additionally, the roof must have only a few penetrations such as skylights and boots and cannot have walls that butt up to the shingles. The flashing should be minimal. The roofing contractor or home inspector that performs the inspection should advise on if the installation of an additional layer is possible.

4 Things that should be considered if you are purchasing a home with multiple roofs or looking to purchase a nail over roof.

1.) Your roofing contractor or home inspector from a reputable home inspection company most likely cannot thoroughly inspect the sheathing aka underlayment. Attic visibility may be minimal and or the roof may not be walkable/visible.

The roof decking which is also known as the sheathing and or underlayment will be covered by asphalt shingles. If you plan on installing an additional layer of asphalt shingles the roofing contractor and or home inspection companies may not adequately inspect the roofing underlayment. If the roof is walkable, it is a good idea for the home inspector to attempt to find soft spots on the roof underlayment. The roofing inspector should peek in the attic to see if there are any signs of previous leaks and or damage to the decking that may compromise the integrity of the roof decking. If the roof inspector/home inspector is wrong about the condition of the roof decking and a 2nd layer of shingles are installed this may lead to the roof system to prematurely fail.

2.) When performing a nail over roof on an existing roof the contractor is relying on the old flashing.

Flashing is the metal that surrounds penetrations such as chimneys, penetrations and skylights. If a roofing contractor roofs over an existing roof they are relying on the old flashing. If the flashing is compromised, rusted and not watertight or properly shedding water this will affect the quality of the nail over roof. If the flashing fails it will lead to spending more money on removing the newly installed nail over, repairing the leaky flashing then re-installing the roof. It is crucial that the home inspector can get a good idea on all of the components of the roof.

3.) If you are upgrading from a 3-tab roof to architectural shingles, it may look bumpy and distorted.

Your roofing contractor should advise the cosmetic look of the new roof when installing architectural shingles over 3 – tab shingles. The cosmetic deformity is due to the difference in designs between the 2 different shingles. If you plan on performing a nail over roof, make sure it is the same type of shingle vs changing shingle type. Your local home inspector or roofing contractor can advise on different scenarios. Additionally, reputable home inspection companies can advise further.

4.) The new roof will most likely not qualify for manufacturer warranties or labor on repairs.

Most asphalt roofs come with a material defect warranty. Additionally, your roofing contractor typically will not offer a warranty on the labor for installation. Reason being the nail over roof is going over an old roof. The roof can prematurely leak due to hidden defects under your shingles that are not visible such as warped or rotted roof underlayment, cracked decking and or undersized underlayment etc.

Now that you are aware of things to consider prior to purchasing a nail over you want to make sure this option is right for you. It may be in your best interest to have a full roof replacement as the nail over roof can prematurely fail, have little or no warranty coverage and or worst-case scenario will need a full replacement eventually due to the condition of hidden defects. If you are purchasing a home in Upstate New York, it is crucial to have a home inspector ffrom a reputable home inspection company who has experience inspect the roof prior to purchasing. Additionally, there are a bunch of roofing companies out there in and around Nassau NY that can properly educate you on your options. We recommend you search google, look at reviews and talk to a few roofing contractors and or home inspectors that can provide you with the information needed to make an informed decision.

Here is a good video on how to tell if you have multiple layers on your roof.

Shield Guard Home Inspections is a local home inspection company. If you have any questions give us a call today!

(518) 649-9111


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