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.
How many layers of roof shingles are allowed in ohio.
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.
In the portland area as of 2018 the current code allows up to three layers if the current layer is in good condition.
Shingles are the element that most homeowners are familiar with as it is the layer you can see from the outside of your home and it is an important aesthetic aspect.
Adding this membrane isn t an option with a re roof and the extra layer of shingles offers little protection against ice dams.
For instance ohio code chapter chapter 4101.
Most cities and towns allow a maximum of two layers of shingles says chad muth president of muth company roofing in westerville ohio.
On most flat roofs such as epdm tpo or modified it is perfectly acceptable to two layers of roofing.
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.
Asphalt shingles typically can have one more layer added over the top two roofs total.
The soundness of the building you re re roofing is another consideration.
3 tabs are less expensive but also less durable have lower wind resistance and have a flatter appearance.
In snowy climates most new roofs these days get an ice and water shield a rubbery moisture membrane applied to the sheathing along the eave to protect against ice dams.
The 2006 residential code of ohio rco states in section r905 2 7 1 states that when table r301 2 1 criteria so designates an ice barrier that consists of at least two layers of underlayment cemented together or of a self adhering polymer modified bitumen sheet shall be used in lieu of normal underlayment and extend from the eave s edge to a point at least 24 inches from the inside of the exterior wall line of the building.
Section 1511 3 requires that roof replacement shall include the removal of all existing layers of roof coverings down to the roof deck but it does lay out a series of exceptions.
For closed valleys valleys covered with shingles valley lining of one ply of smooth roll roofing complying with astm d 6380 and at least 36 inches 914 mm wide or types as described in item 1 or 2 above shall be permitted.
The bottom layer shall be 18 inches 457 mm and the top layer a minimum of 36 inches 914 mm wide.
Finally consider whether reroofing over the old shingles is even allowed where you live.
However this depends upon the roof materials.
For many years it was acceptable to put even the third layer.
Steep sloped roof products such as tile slate metal and shakes only allow one layer.
Asphalt shingles come in two major types 3 tab and architectural.
Adding a second or third layer of shingles adds significant weight to the structure.
