In Seattle there are a lot of older homes with partial basements. The rest of the house will typically have a crawl space under it.
Ever since we started putting basements under houses people have wanted to use these basement spaces for all kinds of things. Typically they started out as a place for the furnace and other utilities. People quickly realized these spaces would also be a great place to put the laundry. The next obvious thing to do with these spaces was to turn them into living spaces—-rec-rooms, bedrooms, work-shops, grow-ops—-you name it.
The various transformations of these basement spaces were more or less successful depending on several variables. There might be height considerations, light considerations, egress considerations and moisture considerations—-to name a few. Often these changes of use would not meet current standards, and some represented serious safety issues.
This post is not really about all of these considerations—-I will save them for another time.
The space between the basement area and the crawl space was often simply open to the basement—-at least originally. There sometimes would be a little short wall to hold the dirt back where it stepped up to the crawl space height. Other times it was just a gradually sloping earthen embankment as the basement area transitioned to the crawl space.
Finishing off the basement required dealing with this slope. Sometimes people would dig away the slope in the crawl space area and build a wall to retain the dirt. This increased the size of the basement space while providing a means of retaining the dirt.
Some of these walls were more satisfactory than others.
Often, the masonry or concrete retaining walls would not be tall enough. On top of these walls people would build a wood wall to close off the basement space from the crawl space area. If the foundation wall does not go high enough, the un-retained dirt wall inside the crawl space, over time, collapses against the wood wall—-resulting in decay/rot and places where wood destroying insects can “party-down.”
I think you can get the idea from the next couple of pictures.
The solution? Proper retaining walls and clearances need to be created, and the solution would vary with the installation.
By Charles Buell, Real Estate Inspections in Seattle
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You should see my crawl space. Of course I used FDN treated wood.
Glenn, I would love to see your project some time!
Thanks for this – I didn’t realize this common approach was used more than locally! Areas where the retaining wall end and the space to the above floor system is filled in with wood is often a problem. Old standards didn’t require any vapor barrier, and when the crawl-space portion is vented to outside air, you have the potential for a lifetime of humidity problems – all soaking into the wood ‘wall’. Even if they don’t look damaged from the basement side, an inspection from the crawl space side can often find substantial fungal growth.
We here in the NW have had a requirement for a vapor barrier for a long time—it is essential in my opinion.
Hello Charles. In my area, Victoria, BC, there is usually an outcrop of granite in that dirt area of the crawlspace. Nowadays, they will drill and blast to get a larger basement space, but before the 70’s, the house sits halfways on a rock with a bit of a basement. There will always be water seepage coming off the rock flowing into the basement. Stopping the water before it reaches the house seems to be next to impossible.