Want Proof That Termites Are (Misplaced) Evil?

I recently had a structural inspection that showed (once again) how much damage a gang of termites can do to a home. This damage was located in the rim joists and sole plates of a home with brick veneer. However, these termites had incentive to invade the wood due to the rim joists and sole plates being apparently exposed to excess water coming from behind the brick veneer.

Some background is needed before getting into the termite business. The sole plates are the boards that sit atop the foundation, upon which the first floor joists rest. Rim joists, also known as band joists, are the boards that box in the floor joists. The ends of all floor joists resting on the sole plate but up against rim joists. Rim joists also help stabilize the joists and help keep them from angling or twisting.

In a properly designed brick veneer wall, a gap is supposed to be installed between the brick veneer and the exterior wall sheathing. The exterior sheathing is the material that covers the outside face of the wall framing. Sheathing can be boards (in older construction), or plywood or oriented strand board (OSB) panels, although in some construction Styrofoam panels may be installed between the plywood or OSB panels. The gap between the exterior sheathing and brick veneer is supposed to serve as a drainage plain to provide water that gets past the brick veneer a drainage path to the base of the wall. And, believe me; water can get past the brick veneer, particularly if the brick is especially porous. Drainage holes (in combination with flashing) in the brick veneer just above the foundation in the brick veneer are supposed to provide a path for water to flow out of the drainage plain. Brick veneer installed on concrete block construction, more commonly used for commercial construction, is also supposed to have a drainage plain with weep holes.

Full brick exterior walls, such as those on many old buildings in Cincinnati, do not need weep holes because the water supposedly travels fully through the brick into the interior wall surface or back out to the exterior surface. Another brick construction that was usually not built with drainage holes was concrete block on a concrete foundation with brick veneer installed in front of the block. Unlike the previously described brick veneer/concrete block wall, the first floor framing in this construction was built on the block and the upper floor framing was built above that. The brick veneer in this construction extended from the concrete foundation and up the exterior wall. This last construction, as used for a crawlspace construction, is the subject of this blog post.

Let’s start with a photo of the foundation construction from inside the crawlspace, shown below:

This photo shows the concrete foundation with the concrete block above it. On the exterior side of the foundation, the soil level would be to the top of the first row of concrete block above the foundation. Now, take note of the dark streaks on the facing concrete foundation. Those streaks are due to water drainage through openings in the block mortar. The question is from where is that water coming. For sure, water can migrate from the soil through the block. But, the darkened block in the area in the corner area and along the foundation to the left that extends the full height of the block hints at another source—the drainage gap behind the brick veneer. Darkening of the block indicates that they are water-saturated. Further support for the drainage gap being a water source is evident from the darkened sole plate wood sitting on top of the darkened concrete block.

Let’s take a closer look at part of the area along the facing foundation. Note the copper water pipe in the photo above. This pipe is the same as the one shown to the left in the photo below. In this photo, the darkened woods of the sole plate and rim joist above the water-saturated concrete block is visible. However, also visible are darkened areas in the subfloor boards on top of the joists. The material that looks like resin or droplets is water droplets on the wood surfaces. The pattern of the water stains on the subfloor indicates that the water source is the exterior wall, and more particularly the drainage gap behind the brick veneer. Areas like these were found all along the exterior walls of this crawlspace foundation.

So, what do these findings have to do with termites—as it turns out, a lot. Termites are one of Nature’s maintenance creatures. They reduce wood back into a form that is useful to plants, microflora and soil. The trouble is that they cannot distinguish between the dead wood of a tree in the forest and the lumber we use in our buildings. The subterranean termites we have in the Cincinnati area also require water to live. In fact, they build mud and frass tubes in areas where they would be exposed to air to conserve water and will carry water from the soil into the tubes to keep them damp enough. In the photo below, the dark streaks on the foundation are the remains of such tubes between the ground and the sole plate. Note that the distance between the ground and the sole plate in the photo is about 5 feet. Termites can be very determined to find a food source.

If termites can find wet wood, their job gets much easier because they do not have to bring as much (if any) water up from the ground. So, in the case of this home, they found it in the wet sole plate and rim joist woods. And once they set up their work area in them, they went to town. The following photos show some of the visible damage. Note in all of these photos that the wood is darkened due to water exposure.

I want to emphasize the words “some of the visible damage.” The exact extent of the damage generally would only be known when the damaged wood is removed and inspected. An ice pick or awl can be used to probe the wood and somewhat determine the extent of damage. If the damage is on the other side of solid wood, though, this method would not find it. Also, termites form multiple tunnels in the wood, which means that unless the wood has been greatly degraded by the tunnels, as in the photos, a lot of probing would be needed to fully determine the damage. More sophisticated and expensive methods to determine the extent of damage exist, such as injecting chilled or heated air into the termite tunnels in the wood and viewing the wood using a thermal camera. In theory, the air would follow the tunnels and provide a temperature difference within the wood that is visible to the camera. The common method, however, is using a probe.

The damaged wood in this home will need to be removed, which will be expensive due to where it is located. The repair will also not be as ideal as new construction. Even worse, as wood is removed, more damaged wood that is not readily visible might be found, making the project much more expensive.

But, a question still exists as to why the sole plate and rim joist wood is getting wet when the wood is at least 16 inches above outside grade. Additionally, the drainage plain behind the brick should extend below the wood to the concrete foundation level. I believe that a couple of possibilities exist. The brick might not have a proper drainage plain, in that the brick veneer is right up against the exterior sheathing. I hope not because that likely means the exterior sheathing and upper floor framing could have moisture and/or termite damage. Another possibility is that the rim joists and/or sill plates block the drainage plain. Then again, water from the upper drainage plain may be filling up the concrete block and/or the gap between the brick and block to the level of the wood. Overall, though, the fact that the subfloor appears to be getting wet indicates that a drainage plain issue is present. When the wood is replaced, the real water source might be evident.

What are the morals of this story? Here are a few:

• Damp crawlspaces or basements can be an invitation for termites to move in.
  
• Properly designed and installed drainage plains behind exterior finishes, whether brick veneer or siding, can help prevent expensive repairs.
  
• A great amount of water can penetrate through brick.
  
• Trick observation—the crawlspace floor was muddy apparently due to water flowing into it. Since no vapor barrier was present, water from the wet soil can evaporate and enter the home where it can cause mold growth in those dark and quiescent locations where mold likes to hang. Then again, even a vapor barrier might not help if too much water is getting into the crawlspace.
  

Unfortunately, like most projects of this kind, I will not know the outcome due to the nature of these kinds of projects. Be assured that if I hear anything, you will be the first to know.