I have a 1949 1600 sf under roof with 8 12 pitches valleys and hips 2 6 rafters on 16 on center sheathed with 3 4 center matched lumber going over at least 1 layer of 3 tab shingles a partial tear took off the old tabs and left a nice wavy surface in pretty good shape.
My roof has 4 layers.
On 4 12 or greater slopes the balance of the roof shall be one layer of 15 felt.
It must be installed the full length of all valleys.
Steep sloped roof products such as tile slate metal and shakes only allow one layer.
Here are the layers of a roof in order of application bottom to top.
Decking most often made out of plywood this roof layer is installed over the framing in a typical roof install.
Asphalt shingles typically can have one more layer added over the top two roofs total.
Roofing material is where most homeowners focus their attention with hundreds of materials styles and color to pick from.
If your roof is in good shape but has some damage to one side from a downed tree or has lost shingles in a wind storm an overlay is worth considering.
On roof slopes of 2 12 to 4 12 the remainder of the roof shall be two layers of 15 felt applied in shingle fashion or 1 layer of ice dam protection.
You can usually see the underside of plywood decking from the attic.
If it needs to be replaced the insurance policy will only cover the replacement of the top layer.
For many years it was acceptable to put even the third layer.
This other carrier would charge me quite a bit because i d only have homeowners insurance with them and they re supposedly the only ones who will deal with me concerning the roof.
Pros to overlaying a shingle roof.
But contractors who spoke with angie s list say best practices call for stripping the roof down to the wood deck to inspect it before installing a new roof.
Stripping away the old roof more expensive because of the additional labor and materials peeling off the old roof down to the sheathing is your only option if you already have two layers.
Most building codes allow this but is it a good idea.
The five main types of roofing materials are asphalt shingles cedar shakes concrete or ceramic tiles metal sheets and rubber used for flat roofs.
Most cities and towns allow a maximum of two layers of shingles says chad muth president of muth company roofing in westerville ohio.
Here are the pros and cons.
If the roof has multiple layers typically the insurance company will only insure the top layer.
On most flat roofs such as epdm tpo or modified it is perfectly acceptable to two layers of roofing.
I was told by my insurance company that they don t cover a roof that has three layers of roof shingles on it so i ve gone to another carrier for an estimate.
First of all multiple layers of shingles simply means layering a new asphalt shingle roof on top of the old one rather than stripping the roof completely to expose the sheathing and replacing it with new shingles.
