If water is entering the basement through the foundation walls, for instance, installing a sump pump and pit below the floor slab will not correct the problem. Similarly, if water is entering the basement through the floor slab, sealing the walls will not solve the problem. Very often, homeowners are talked into a complete basement waterproofing, which can cost several thousand dollars, when simply redirecting the water discharging from the roof drainage system (gutters and downspouts) so that the water does not accumulate around the foundation might do the trick.
A basement water seepage inspection should begin during the exterior inspection. As you walk around the house, record on your worksheet the exact location of any conditions that can cause water to accumulate around the foundation (faulty gutters and downspouts, settlement of walkways, improper grading etc). If there are problem conditions on the exterior, when you go into the basement the walls and floor opposite those areas should be inspected first for signs of water penetration. Even if there are no signs of past or current water seepage, the exterior problem conditions should still be corrected.
There are many causes for water seepage, and a basement can have a water intrusion problem and still be dry when you look at it. For instance, if water enters the basement through the floor slab as a result of a seasonably high water table and the basement is inspected when the water table is one or two feet below the high level, a heavy rain will not raise the groundwater enough to cause water to seep through the floor slab. It takes time for rainwater to seep into the ground and raise the water table.
On the other hand, water puddles or flooded areas in the basement are obvious signs of a water problem. However, in most cases you will not see standing water, so you must make an evaluation of whether there is a condition based on other signs. If you see indications of water seepage, talk to the homeowner about the condition before you rush in and hire a contractor to waterproof a basement. It is possible that whatever it was that caused the past seepage has already been corrected, and if it was fixed by installing buried drainpipes or coating the outside surface of the foundation wall, the correction would not be visible. If the homeowner says the condition has been corrected, ask for a copy of the paid bill, a guarantee or the details of the contractor. If there is a guarantee, ask whether it is transferable.
The best approach to avoid a costly water damage restoration is to immediately correct any obvious problem conditions such as faulty gutters and downspouts, cracks through which water is actively leaking, improper grading etc.
When looking for signs of basement water seepage, check the walls, the floor, the joint between the walls and the floor, as well as the bases of all the items stored or standing on the floor. Look specifically for white powdery deposits on masonry foundation walls and floor. These deposits are mineral salts in the masonry that dissolve in the water as it passes through the walls or floor. When the water evaporates from the surface of the walls or floor, it deposits these salts. This condition is called efflorescence. A thick layer of efflorescence is usually an indication of considerable water seepage.