Siding Leaks into the Basement

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.

Photo 1. Interior bay basement.

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. 

Photo 2. Exterior bay brick.

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.

Photo 3. Cap with no slope or flashing.

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. 

Photo 4. Weep high on the brick.

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. 

Illustration. Masonry veneer flashing.

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.