The following is an article written for our blog by Kent Lambert of Northwest Building Inspection Services. We have used Kent for our personal property inspections for over a decade and highly recommend him and value his knowledge.

The majority of homes in Whatcom County are built over crawl spaces. Most home owners have never entered their crawl space and probably don’t intend to. Checking the crawl space at the time of purchase is the buyer’s best chance to find out what problems might exist.

Crawl spaces are an important part of a thorough “home inspection” and there are several things to be concerned about. Most of the concerns involve moisture and many can be easily controlled.

Ground water seeping into a crawl space is a major concern, especially when the water does not have a place to drain out. The causes of ground water in a crawl space are numerous and not always easy to correct. The drainage at the exterior of the foundation might not have been installed properly or there could be plugged or damaged drainage pipes. In many cases, the drainage pipes are not installed deep enough.

When there is a water problem a crawl space most home inspectors will recommend a drainage expert. There are numerous ways to rectify drainage issues but not all are proper. Correcting the drainage on the exterior of the house can be challenging and difficult (i.e. vegetation in the way, concrete patios and walkways, the depth needed for the drainage pipes, etc.).

Most corrections are made inside the crawl space, typically involving a sump pump and drainage ditches installed to divert the ground water over to the pump.

Because the work is typically done inside the crawl space it is usually not checked by the owner/buyer and sometimes the workmanship is shoddy. Always use a reputable company that will guarantee their work.

Although there are no specific requirements regarding drainage corrections, there are some obvious rules that should be followed. Usually the sump pump is installed in the lowest portion of the crawl space. The pump should be installed in a large perforated container, surrounded with gravel, and the pump’s outflow should discharge either into the exterior drainage system or into a public storm system (the latter is preferred).

Ditches should be installed all around the perimeter of the foundation to catch the ground water that might seep in. The ditches should be deep, with drainage pipes installed that are surrounded with gravel (the gravel should be filled to the top of the ditches). The ditches and drainage pipes should extend to the sump pump. After the completion of the drainage work, 6 mil plastic vapor barriers should be installed over all dirt floor areas.   

Since sump pumps are mechanical, they should be checked and maintained periodically. Unfortunately that means that you or someone you hire must go inside. Some pumps are installed outside the crawl space making them easily accessible.

In some cases where the ground water is somewhat minor, gravel can be installed (first remove the plastic vapor barriers) over the dirt floor areas. The plastic vapor barriers are then re-installed, keeping the ground water underneath, allowing it to slowly percolate out.

Again, your best insurance it to have the crawl space carefully checked and if there is a problem, consult with a drainage expert.

Kent P. Lambert
Northwest Building Inspection Service
InspectingHomes@gmail.com

For more information on Bellingham Real Estate or to search for homes in the Bellingham and Whatcom County area visit www.JohnsonTeamRealEstate.com, your one stop Bellingham real estate and community information resource!