First the basics – Pitched Roofs
The basic structure of a typical pitched roof is: the framework, a deck and a weather resistant covering. The purpose of the deck is to serve as a base for supporting the roof covering, which is what protects the roof. (Pretty simple so far, right?) A pitched roof has a series of parallel beams (joists) joined at the top at angles, like tepees with a supporting overlay (the deck), usually plywood or similar material that serves as a base for supporting the roof covering (shingles), which has the purpose of shedding the water away from the roof either into gutters or just falling off the roofline. The deck is not waterproof so the shingles must be intact and able to withstand all types of weather, (except tornadoes and meteoroids) be it snow, hail, or rain.
I can’t speak for all home inspectors because they have there own techniques and working procedures. Like most people I had a couple of them look over my house, so from my experience they generally do a outside visual of roofs that entails walking around the house, sometimes with the aid of binoculars for close-up viewing or use a ladder for ranch type houses, if practical. They generally don’t want to walk up there for liability issues (fear of there foot going through the roof), but I feel that is the best way to check for roof structural integrity and they need to do it anyway for flat roofs. Needless to say they would be responsible for any damages they do in the course inspection!
A typical roof inspection will include checking for:
Uneven shingles – poor installation of a second layer over an old one. This might be ok but will be prone to water damage. When making an attic inspection the deck should be checked for damage and signs of leakage.
Sagging roof – probably deck damage, but may be a structural problem like a damaged ridge beam (A beam placed on end at the top of the roof and fastened to the rafters) or a roof deck that may not have adequate bracing or spacing of wood-frame support members. This is better left for a structural engineer for evaluation.
Roof ventilation – in a way roofs have to breathe too, that’s why there are roof vents on the roof and in the soffit (a horizontal board nailed to a roof overhang). Warm air must have an escape in attic space or there will be moisture buildup and the wood will rot. This can also cause streaks on interior walls and peeling paint. An inspection should be made of vent placement and count to evaluate if there is adequate ventilation.
Shingles- If the roof is pitched it will most likely have overlapping shingles to shed water away and down the roof. The south and southwest sides of the roof gets most of the sun that makes brittle and age faster, thereby causing deterioration. If there is any cracking, pealing or breakage of these ‘tiles’ they will need repair or replacement because it will not protect the roof.
Flat Roofs
Even if a roof has a slight pitch it is considered a flat roof. As with the pitched roof this is the first thing inspected. Sometimes an interior wall that has signs of water damage could be traced back to the roof. Since this type of roof can’t be seen from the ground inspection must be made at top of the house. On a two story or more building access to the roof has to be made from inside, a stairwell, ladder, or an access hole in the ceiling of a room, probably a bedroom closet or pantry. As with any type of roof ventilation is key so checking for air vents is a must. A ventilation opening can be a pipe coming from the roof top or an open space on the side of the roofline right below the roof. A flat roof differs from a pitched one in that it is water tight, not just shedding water like a pitched one. At one time standing water was considered a good thing because it would cool the roof a bit during the summer months. There should be no ponds of standing water because this could be a breeding ground for insects and more importantly plants, where the roots can break through the asphalt covering. Special attention should me made when inspecting flat roofs because even small cracks between the roofs drain and the roof covering could become serious.
There are many types of flat roofs like single-ply membrane, roll roofing, metal roofs, hot tar covered or built-up roofs an inspecting them is similar in every case. The inspector will look for any visible cracking, blisters, weak spots or any kind of corrosion that will compromise the structural integrity of the roof. The cause of a leak on an interior wall or ceiling may be hard to find because it may have started on the roof, then zig-zagged its way down, but several feet away from the area you saw it.
These are some of the things home inspectors look for and report on when checking roofs. They not only go in 120ºF attics but also crawl under houses, and look in chimney stacks, but do so with a great deal of courtesy and professionalism!
