Roof Leaks: Look for signs of and monitor water leakage from the roof above and try to locate the source. This may be difficult to do beneath built-up roofs or loosely laid and mechanically fastened single-ply roofs, since water may travel horizontally between layers of roofing materials.
Attic Ventilation: Signs of inadequate ventilation are rusting nails (in roof sheathing, soffits, and drywall ceilings), wet or rotted roof sheathing, and excessive heat buildup. Adequate attic ventilation can be measured by calculating the ratio of the free area of all vents to the floor area. The free area of vents is defined as their clear, open area. If a vent has an insect screen, its free area is reduced by half. The free vent area-to-floor area ratio should be 1 to 150. If the calculated ratio is less, consider adding ventilation, especially if you’re in a hot and humid climate.
If the attic also contains an occupied space, check that the ventilation from the unconditioned, unoccupied areas at the eaves is continuous to the gable or ridge vents. Also check that the free area of eave vents is approximately equal to the free area of ridge or gable vents. If ventilation appears to be inadequate and additional vents cannot be added economically, consider adding mechanical ventilation.
Vents and Birds: Make sure ventilation openings are clear of dirt and debris. At larger ventilation openings on a building’s exterior and where louvered grilles are used, such as at gables, check for the presence of 1-½-inch-square 14- or 16-gauge aluminum mesh bird screen. If there is none or it is in poor condition, consider having new bird screen installed.
Plumbing Stacks and Exhaust Ducts: All plumbing stacks should continue through the roof and should not terminate in the attic. The stack pipes should not be loose, broken or damaged. Exhaust ducts should not be kinked, broken or damaged. They should not terminate in the attic but should continue through the roof, gable or wall.
Buried Oil Tanks
A buried oil tank can be concealed by heavy landscaping. Buried ferrous-metal oil tanks are commonly found on older properties whose home and/or domestic water supply is heated by oil. As with all underground items, a buried oil tank is not within the scope of a visual home inspection. The presence of a buried oil tank can usually be determined by finding the fill and vent pipes that extend above ground. Abandoned and very old buried ferrous-metal oil tanks are an environmental hazard.
Once free from the tank, petroleum will sink through unsaturated soil and enter the water table. There, much of the chemical will vaporize and eventually bubble up through the ground's surface. In addition to the risks posed by other petroleum products, leaked gasoline presents the risk of fire and explosion, especially if the fumes collect inside homes and other buildings. Any petroleum-contaminated water that is ingested or used to bathe is potentially deadly. A tank is capable of leaking chemicals for many years, since the corrosion process is typically slow.
If there is a buried tank on your property, the soil around it should be tested by a qualified environmental professional for the presence of oil seepage. If leaking has occurred, the tank and all contaminated soil around it must be removed. A tank that shows leakage must be removed from the ground or filled with a chemically inert solid, such as sand. Groundwater contaminants too must be removed by pumping air through the water, which causes volatile petroleum compounds to vaporize and biodegrade naturally.
If leaking has not occurred, it may still be a potential problem. Even if a tank is empty, it still may have residual oil in the bottom that is a pollutant. Consult with a specialist about the best option for dealing with an underground tank on your property.