However this depends upon the roof materials.
How many layers of shingles are allowed on a roof in ohio.
Most cities and towns allow a maximum of two layers of shingles says chad muth president of muth company roofing in westerville ohio.
905 1 2 ice barriers in areas where there has been a history of ice forming along the eaves causing a backup of water as designated in table 301 2 1 an ice barrier shall be installed for asphalt shingles metal roof shingles mineral surfaced roll roofing slate and slate type shingles wood shingles and wood shakes.
Your three layer roof is definitely a potential structural concern and homeowners insurance companies might consider three layers of roof shingles.
For example cedar or tile roofs are only allowed one layer.
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.
Adding a second or third layer of shingles adds significant weight to the structure.
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.
For many years it was acceptable to put even the third layer.
Metal roof shingles shall be applied to a solid or closely fitted deck except where the roof covering is specifically designed to be applied to spaced sheathing.
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.
Asphalt shingles typically can have one more layer added over the top two roofs total.
That limit pertains to roofs with up to a 4 12 pitch.
1 inch 25 4 mm 1 mile per hour 0 447 m s.
The average 30 square roof uses 90 bundles of shingles and a bundle of asphalt roofing shingles weighs about 100 pounds which means you re putting roughly 9 000 additional pounds of weight on your roof.
Most building codes allow up to two layers of organic or fiberglass asphalt shingles.
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.
Metal roof shingles shall not be installed on roof slopes below three units vertical in 12 units horizontal 25 percent slope.
In the portland area as of 2018 the current code allows up to three layers if the current layer is in good condition.
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.