The Critser Family of Signal Mountain had problems. For many years they lived with a strong musty odor in one particular part of their home. Nothing they did would remove the persistent smell. During the winter the house was very drafty, the floors were cold, and family members were constantly fiddling with the thermostat to keep the house temperature steady. But the real problem came after installing new hardwood flooring throughout her house. Almost immediately, they noticed that their new flooring boards were beginning to cup. Cupping is a condition where the floor boards absorb moisture unevenly along the seams where each board meets another. The individual floor boards swell and distort forming unsightly alternate low and high spots in the board. Alarmed, Charlotte asked us to take a look to see if we could help.
From experience, we knew that these problems are almost always caused by moisture, and because the problems seemed to be happening throughout the entire first floor, it pointed to the crawl space.
In the crawl space, we immediately discovered evidence of running water with large areas of saturated ground where water had pooled. Most of the ground under the house was damp or wet as well, and most of the block foundation walls were saturated with water where they came in contact with the ground A thin plastic ground cover meant to function as a vapor barrier was torn, scattered and disheveled. Floor insulation between the floor joists was wet with condensing water and hung like stalagtites . Dark mildew covered much of the underside of the plywood subfloor and wood framing. Iron water and gas pipes were coated with rust. There was an overwhelmingly strong musky odor and breathing was difficult. We checked the relative humidity using a hygrometer. It was over 95%. Since water vapor condenses at 100% relative humidity, we knew that the crawl space humidity was often at that level. By contrast, the humidity inside and outside the house was under 50%.
Further inspection revealed that the houses’ foundations were built on top of porous mountain stone. An inspection of the outside of the home showed that the home’s back yard had negative drainage, meaning that it drained into the back of the home, as opposed to draining away from the home. When it rained, the ground water at the back of the home easily entered the crawlspace, pooled and receded slowly, leaving the ground under the house saturated. This set up a micro-climate under the house that ensured the high humidity. It is this constant high humidity that created an environment that promoted the growth of mold, mildew and rust and caused the problems with the flooring. Left alone, the dampness in the crawlspace would continue to make the floor and the home interior environment worse.
The Solution:
We might first have started by regrading the back yard to create a positive drainage away from the house. However, the entire back of the house was covered by a large deck, so this was out of the question. Any solution would have to take place under the house.
The first step was to completely clean the crawlspace, which had been used for storage of excess building supplies and lumber. All materials were removed along with the old shredded vapor barrier, and all saturated flooring insulation.
Second, we sprayed all exposed wood framing with fungicide to kill the mold and mildew. A perimeter French drain was then dug and installed around the interior of the foundation using solid perforated pvc pipe, laid into the trench and covered with geofabric cloth and gravel to collect, contain and channel water to a sump pump which was installed at the lowest part of the crawlspace. Now, when it rains, any running water will be channeled and pumped out of the crawlspace.
We then smoothed the ground in the crawlspace. Next , we insulated the interior masonry foundation walls with 2” foam insulation, leaving a 3” gap at the top to allow for future termite inspections. We closed, filled and insulated all foundation vents and floor rim joists, which prevented air infiltration from the outside.
Lastly, we installed a 16 mil reinforced liner over the ground and up the foundation walls, completely encapsulating the crawl space to keep all moisture out of the airspace. All seams were taped. The liner was taped and mechanically fastened to the masonry foundation walls to keep it in place permanently. Normally a 6 mil clear household plastic is used for this purpose. However, as evidenced by the condition of the existing vapor barrier, these types of vapor barriers just cannot hold up over time. The thicker, reinforced products are similar to pool liners and are very tough and resistant to damage and water penetration.
After completion of the project, which took about a week, the change was immediate and remarkable. The relative humidity in the crawlspace immediately fell to 45%. The temperature in the crawlspace rose to 60 degrees. The air was fresh and clean. The odors ceased, and now the space remains dry even during and after heavy rains. “I am very pleased,” says Charlotte. ”The smell is gone, and my house is much warmer. It used to be so drafty during the coldest days, but now the temperature inside is very stable. We haven’t played with the thermostat at all since the work was completed. And best of all, our floors have returned to normal”.
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