Most building codes allow up to two layers of organic or fiberglass asphalt shingles.
How many layers of shingles are allowed on a roof in illinois.
For example cedar or tile roofs are only allowed one layer.
Adding a second or third layer of shingles adds significant weight to the structure.
Your three layer roof is definitely a potential structural concern and homeowners insurance companies might consider three layers of roof shingles.
Roofing layers from the framing to the shingles.
Regulations allow a maximum of two layers of shingles on a roof but experts say you shouldn t lay asphalt shingles over an existing roof.
The weight of 5 layers of shingles on a roof is a bad thing in itself surely in snow country.
In most cases two layers of shingles is advisable and three aren t normally required but if you live in an area that suffers from particularly strong wind or lengthy periods of heavy rain then you may want to consider a third layer.
There are a few reasons why i don t like multiple layers of roofing shingles on a roof.
When it s time to replace your roof there are several factors that might lead your roofing professional to recommend adding shingles on top of your existing layers.
Some municipalties allow only two layers.
That limit pertains to roofs with up to a 4 12 pitch.
If the current roof is in poor shape re covering may not be a sound choice.
Other factors to consider.
A roofing contractor will know exactly how many layers of roof shingles are allowed in your area for your building but it is normal that you will be permitted up to three layers of shingles.
The shear weight of multiple layers of roofing shingles can cause stress on the framing of a roof and could cause truss s or rafters to bow and or break.
When it s time to replace the roof again and you have no choice but to start anew two layers is the maximum allowed in most areas you ll have to pay extra for the two layer tearoff and disposal.
Eliminating the tearoff can easily save 1 000 or more on a new roof but you re really just delaying the cost.
The soundness of the building you re re roofing is another consideration.
For example there s a starter course of roofing shingles installed at the eaves before the roofing shingles you can see.
The building code throughout most of illinois is 2 layers of roofing shingles are allowed.
I don t know whats legal in illinois but the general rule on roofing is a max of 2 layers on a roof.
According to the international existing building code homes can be re roofed one time by applying a second layer of roof shingles over the existing one but after that application begins to wear both layers need to be removed before a brand new roof is installed.
Some municipalties allow only two layers.
