Flat roof systems and coverings have evolved considerably over the years. I remember the time that rolled asphalt was used primarily for flat roof coverings. And many times that was installed incorrectly. As a home inspector, I see many flat roof coverings, even with acceptable materials installed improperly. First off, there should not be an actual “flat” roof structure. Roof structures should have some pitch. The structure should not be built with a 0/12 pitch. Keeping standing water off this type of roof is impossible even with proper drainage. Even the smallest leak will be disastrous. Low slope / flat roof structures should slope approximately ¼ inch per foot. Many inspectors refer to a low slope / flat roof structure as having a pitch of less that 4/12. Although some roof shingle manufactures will warranty their shingles (if certain underlayment is properly installed) on up to a 2/12 pitch roof. However, home inspectors will not know if the proper underlayment was installed correctly. Installing a low slope / flat roof covering is something all roofing companies say they do, however this installation involves using the proper materials with a high degree of skill. The requirements for low slope / flat roof coverings are different than a pitched roof. I normally recommend a single ply membrane.  Here are the trouble areas and what a home inspector should be looking for:

• Ensure there is some degree of slope and proper drainage
• If roof drains are employed closely check to ensure they are sealed
• Look for the installation of a clamp ring drain that will seal better than a conventional drain
• Roofing material should extend at least 8” up an joining wall or window sill
• Roofing material should be installed 18-24” under shingles where a pitched roof joins a low slope. Ensure shingles are not installed to low and nailed into the membrane
• Lifted or bubbles in the membrane
• Repaired areas or tar
• Metal flashing should be used for brick walls and be let into or cut into the mortar joint
• Stucco / EIFS; metal flashing should be used under the lower drainage section
• Roof drains should be avoided if possible and exterior gutters or scuppers should be installed. Proper flashing should extend from the roof covering into the scupper
• Parapets should have roofing material installed over them and capped with a metal flashing
• Skylights should be installed with the roofing material extending up the side and capped with a proper gasket or manufacture supplied flashing
• Penetrations should have pre-formed flashing not tar
• The leading edge should have roofing material under the drip edge and over the fascia. Drip edge would then be sealed with another piece of roof membrane over the top of the drip edge
• Ensure there is not a raised edge at the leading edge that would cause water to  back up or not drain properly

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