If you are unfamiliar with how roofs are constructed, you may assume all that's there is the top layer of roofing shingles. There are many more layers that make up your home's roof that you may not be aware of. Here is what you should know about roofing layer and layover options.
A roof starts with the trusses at the bottom, which is a home's framework and essential to forming the shape of the roof. On top of that is a thin layer called particleboard that attaches to the trusses, which gives the roof a solid base to secure the rest of the roofing material. Roofing felt is placed on top of the particle board to help prevent it from being damaged by moisture.
An underlayment material is installed on top of the roofing felt, which is an additional layer made out of rubber that helps protect your roof from moisture. Some homes have both roofing felt and underlayment material, while others just have the rubber underlayment. It is common for metal roofs to not have the additional layer of roofing felt because it is not necessary due to how waterproof the metal material is.
On top of all of those layers are the shingles that are nailed to the roof's surface. Where things get more complicated is when homeowners decide to not rip off the old material when installing a new roof, which is known as a roof layover. While it is acceptable to perform a roof layover, it is not always the best option.
The new roof is installed directly on top of the old material, with no additional waterproofing barriers placed between them. Leaving the old roofing material on the roof means that the roofing contractor is unable to properly inspect the roof deck, roof felt, and underlayment material for damage. A layover roof can be a quick fix to roofing problems but can lead to more problems down the road. If the new roof leaks water through the top layer, it can easily reach the trusses and particle board if there is an existing problem that wasn't fixed.
Some cities have residential building codes that prevent roofing layovers from being installed, or limit the number of roofing layovers to a single layer. This will help ensure that the roof eventually is replaced by ripping off all the material and that a proper roof inspection is performed.
If your roof needs additional attention, contact local companies like Horizon Roofing.