How Many Layers Of Shingles Should Be 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.

How many layers of shingles should be on a roof.

A roofing contractors 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 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. Underlays are quickly applied and they can provide temporary roofing before the roof shingles are installed. Eliminating the tearoff can easily save 1 000 or more on a new roof but you re really just delaying the cost.

Roofing layers from the framing to the shingles. On most flat roofs such as epdm tpo or modified it is perfectly acceptable to two layers of roofing. Asphalt shingles typically can have one more layer added over the top two roofs total. Your three layer roof is definitely a potential structural concern and homeowners insurance companies might consider three layers of roof 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. That limit pertains to roofs with up to a 4 12 pitch. For many years it was acceptable to put even the third layer. Resins from green lumber roof decks have been known to interact with roof shingles and a separation layer of underlay can be useful.

For example there s a starter course of roofing shingles installed at the eaves before the roofing shingles you can see. For example cedar or tile roofs are only allowed one layer. So we ll start at the bottom of the deck and work our way up through all the roofing layers until we reach the shingles and sunshine above your roof. However this depends upon the roof materials.

Most building codes allow up to two layers of organic or fiberglass asphalt shingles.