Basement leaks can be caused by improper installation of siding, brick and flashings. Let’s look at a typical example.
Basement leaks high on the wall
Water stains begin high on the foundation wall below a bay (Photo 1). At times, water runs down the wall and puddles on the floor. The owner stated that this 19-year-old home has always leaked. The original builder corrected the leaks with exterior caulk, but the wall still leaks with wind-driven rain. This area has a small roof overhang. and the bay faces the direction of most wind-driven rain.
What’s going on outside?
Outside the bay (Photo 2), the finishes are in good shape and well-maintained. But let’s look closely at flashing details.
At the top of the brick (Photo 3), the veneer cap has no or very little slope away from the building. The vertical trim extends behind the brick, with no flashing over the brick. The small flashing below the wood siding is caulked to the siding. All of these improper details allow water to penetrate behind the brick.
Down at ground level
I dug out some soil to examine the joint atop the basement block–brick veneer and the weep hole (rope) (Photo 4). There is no visible flashing at the bottom of the brick veneer. The weep should be at the bottom of the brick. Note that builders commonly bury the lower veneer flashing in the mortar joint so it will not be visible. I think that’s a mistake.
Flashing done right
When flashing is properly installed, it should direct water over the top of the brick (Illustration). While there may not be flashing over the full length of the veneer, as shown here, there must be flashing at the base of the veneer, with a weep at the bottom of the brick to drain water.
In this case, we don’t know whether a moisture-resistant barrier was placed on the wall and layered properly with flashing. We do know that skimpy overhangs and exposure to the rain from most rainstorms, combined with poor construction details, cause the leak in this basement.
Your takeaway as a home inspector
Always note missing horizontal flashing, improperly caulked flashing, and stains or leaks on basement walls. Your note might say “potential for leaks—suggest further evaluation” or “signs of extensive leaks—requires further evaluation.” A visual inspection does not include digging into the soil or exposing moisture-resistant barriers.
Keep in mind that all siding leaks, so flashing must be used to protect the wall assembly. Remember that signs of leaks in siding and bricks can appear in the basement.