LOW SLOPE ROOF SYSYEMS
A client called for an inspection last week and was concerned because the house did not have a roof. Actually the house did have a roof and the reason the client was not able to see the roofing on the roof structure was because the house had a low slope roof. This system is also commonly referred to as a flat roof.
It is critical during the inspection process of a flat roof to actually achieve access to properly determine the condition of the roofing. This can be challenging if the inspector does not have the proper equipment or if there is not interior access to multi-family two or three story buildings. Good inspectors will contract with a boom truck to gain access. Sometimes multiple ladders may be needed to go from roof to roof or rear deck to roof to gain access. No matter how challenging it is, the inspector must gain access to properly report on the conditions of the roofing for the client.
Even though these roofs are sometimes referred to as flat roofs, there should always be a minimum amount of slope directed towards a means of roof drainage to prevent water intrusion to the interior spaces. This is true even though low slope roofs use water tight membranes as opposed to the asphalt composition shingles used on steep pitched roofs that shed the water. If there is no slope or drainage system, it is highly likely that this roof will always leak.
The materials used on today’s low sloped roofs have changed and improved over the years, but the concept is still the same. The system generally starts with either metal or wood decking, topped with a rigid layer of foam insulation or a base sheet that is attached to the roof deck. Roll roofing, Built up roofing, Modified Bitumen roofing, and Sprayed Polyurethane Foam are some of the most common type roofing materials that you will typically see on these type roofs. Your inspector will be able to advise you on the advantages and service life on these type materials.
The inspector will typically report on blisters or bubbles, splits in the membrane, inadequate seals around roof penetrations, cracks or (alligatoring) in the membrane, and signs of water ponding. If a roof or sections of roofing have been repaired repeatedly, there is a good chance that there is a leakage problem that is either still active or will be again.
Generally speaking low sloped roofing does not have as long a service life as pitched roofs with composition roofing shingles. Ask your inspector to take as many photos as needed to confirm his findings. Buyers do not want to install new roofing one week after closing.
Harry O. Morrell
ASHI Certified Inspector
