The technique used for inspecting the roof differs depending in whether the roof is flat or pitched. A pitched roofs inspection is performed during the initial pass around the house, but because of the safety hazards involved it is not recommended to climb onto a pitched roof. Start your inspection by stepping far enough away from the house so that you can see all exposed sections of the roof as you circle the structure. Use binoculars to get a close-up view of the roof. As you walk around the structure looking at the roof, note any uneven, sagging or damaged sections.
Unevenness might indicate warped sections of deck or a poor installation of a second layer of shingles. Generally this condition is not a problem, but shingles in uneven areas are more vulnerable to damage and water intrusion, so check for signs of leakage inside also. Use a worksheet and make a note of the approximate locations of the uneven areas. During the attic inspection, check these areas for signs of leakage inside and to verify the cause of the unevenness.
Damaged sections can occur from falling tree limbs or swaying tree branches that overhang the roof. Record the location of each damaged section in your worksheet, as it must be repaired. Generally, patching the damaged area will suffice.
Walking your way around the roof, check the roof ventilation system. Ventilation of the area below the roof deck is extremely important, especially in newer buildings where the deck is constructed of plywood panels instead of tongue-and-groove boards. If this area is not properly ventilated, a moisture buildup can eventually cause the plywood sheathing to delaminate. This moisture problem is even more acute in buildings that have cathedral ceilings constructed by nailing plasterboard or an equivalent type of panel directly to the roof rafters. Above the ceiling there is insulation, and above this is the roof deck. Often, there is a small air space between the insulation and the deck. When moisture normally generated by cooking or bathing reaches the area of the deck, if there are no vent openings through which it can escape it will cause rot and delamination.
Many homes built with this type of cathedral ceiling have inadequately ventilated roof structures. If your house has a cathedral ceiling with no vent openings near the bridge, expect problems with the roof deck. You can notice if you have a deck problem by walking on the roof. If sections of the deck yield with each step and feel soft and spongy beneath your feet, you have some problems there. Still, remember that you should not attempt to walk on the roof if the pitch is steep of the shingles are a type that can easily damaged, such as slate or tile. Also, if the roof is not easily accessible from a deck or an intermediate-level area, leave this part of the inspection to a professional. Even if the roof deck shows no signs of a problem, if the area does not have adequate ventilation near the top of the roof consider installing a ridge vent to prevent future problems.
Pitched roofs are usually covered with shingles applied in an overlapping manner, but these shingles are not intended to be watertight. They protect the structure from rain intrusion by shedding water. The most common types of roof shingles are made of asphaltic material, wood, asbestos-cement, slate and clay tiles. When walking around the roof during your inspection, pay particular attention to a slope that has a southerly or southwesterly exposure. Since shingles are designed to just shed water, any water that gets under them will leak into the interior of the structure. Shingles that are lifting, cracked or broken are vulnerable to water leakage. If you see any signs of leakage inside, it is a clear indication that maintenance is needed.
Pitched Roofs Inspection According to Roofing Materials
Pitched or steep sloped roofs can be best inspected when direct access is possible to all their surfaces. For areas that are inaccessible or cannot be walked on use binoculars. Look for deteriorated or loose flashing, signs of damage to the roof covering, as well as valleys, drainage & gutters clogged with debris. Examine exterior walls carefully and trim for deterioration beneath the eaves of pitched roofs that have no overhang or gutters. There are four categories of pitched roofing materials, and their condition should be checked accordingly:
Asphalt Shingles
Asphalt or composition shingles have a service life of roughly 20 years for the first layer and about 15 years for a second layer added over the first one, depending on their weight, quality and exposure. Shingles should be replaced when they begin to lose their granular covering and start to curl. Normally, no more than two layers of asphalt shingles should be in place at a time. If a second layer of asphalt shingles has been applied, check to see if all flashing materials (aluminum, galvanized steel, rubber) in the first layer were removed and replaced with new flashing at the second layer. Check the roof slope – a slope of 4 in 12 or steeper is considered normal, between 3 in 12 and 4 in 12 is considered low, and no asphalt shingle should be less steep than 3 in 12. If the roof has a normal slope, check the underlayment as well (if possible). It should be at least a single layer of 15-pound (6.8 kg) asphalt saturated felt, while low-sloped roofs should have at least two such felt layers.
Wood Shingles or Shakes
Wood shingles or shakes have a normal life expectancy of 25 to 30 years in climates that are not excessively humid and hot, however durability varies depending on wood species, thickness, roof slope, whether shingles are made from heartwood, and whether they have been periodically treated with preservative. Shakes are hand-split on at least one face and either tapered or straight, while shingles are sawn and tapered. Check the roof slope – the minimum slope for wood shingles is 3 in 12 and for shakes 4 in 12. As both wood shingles and shakes age, they dry, crack and curl, and in damp locations they rot. When more than one third show signs of deterioration replace them. Note that these roofing materials are easily broken, so they should not be walked on during the inspection. If the roof is historic or relatively complex, consult a wood roofing specialist.
Metal Roofing Inspection
Metal can last up to 50 years or even more if properly maintained. Metal roofs may be made of galvanized iron or steel, aluminum, copper or lead, and each of these roofing materials has its own unique wearing characteristics. Metal roof shingles should be inspected for signs of rusting or pitting, corrosion due to galvanic action and loose, open or leaking seams and joints. The slope can be from one-half inch per foot (1:24) to very steep. The types of metal, seams and slope determine the construction details.
There are three main types – batten, standing and flat – as well as flat and formed metal panels. Snow guards must be installed on steeper slopes, while in locations with heavy, long-lasting snow bracket and pipe snow guards may be necessary as well. When it comes to low-slope metal roofs that are coated with tar-like material, they are probably patched or have pin holes and cannot be counted on to be leak-free. Again, if the roof is historic or relatively complex, consult a metal roof professional.
Slate, Clay Tile, Asbestos Cement Shingles
These roofing materials are extremely durable, and if properly maintained they may last the life of the structure. The minimum slope for roofs of these materials is 4 in 12. Slate shingles should be secured by copper nails, except in the very dry climates. To check the structural integrity of these roofs, look at the underside of the roof sheathing in the attic or check the nails on broken shingles. Nail heads should be covered with sealant, and nails for tile roods should be non-corroding.
Choosing roofing materials is a very important aspect that will determine the life span of your roof. Any serious repair work should be done by a professional, and any potential issues should be addressed in a roof inspection. A qualified roofing contractor may provide additional structural support.