Expert: Richard Taylor, AIA - 2/22/2006

Question
Hello, thank you for your Q&A service.  

I have a diffcult problem with a wet crawl space and I could use some advice.  The home is a 24x28 story and half log home located 50' from a large lake in MI.  The home was completed 18 months ago and has a concrete block crawl space walls and a 4" poured concrete floor.  The crawl space consistently holds 2" of water and I have seen twice that amount on one occasion.  

Neither my GC or plumber have any solid suggestions for what to do.  The plumber says a sump pump won't work as he belives their is a chance the sump pump would not be able to keep up with the volume of water and that there is not a good place to pump it to.  He belives the water table is higher than the crawl space floor.  There are homes close by on each side making vacating the water problematic.  Addiitionlly, the home has a mound septic system and pumping to the system would cause the septic to degrade and fail.  

Another option I have also considered is using a concrete pumper truck to install another 6 to 8 inches of concrete in the crawlspace to raise the floor.  I only have 36" head room in the crawl space now so I am reluctant to do this.

I am also considering the use of sanitred which is a rubber compound which I would apply to the floor and walls.

Attached is a web link to the house which will give you an excellent visual of how it is sited.

http://www.vacationrentals.com/vacation-rentals/2166.html

Suggestions and recommendations would be very much appreciated.

Thank you

Scott

Answer
Scott - thanks for your question!

You're right, you've got a real problem.  In fact, you have several.  Obviously you want to prevent any damage caused by the water infiltration, but perhaps more importantly, you need to be concerned about the potential health hazards posed to your renters by the presence of moisture in the crawl space - it will eventually result in mold growth in that area.

The solutions you've suggested all have one flaw in common - they deal with the water AFTER it's entered the crawl space.  You need to deal with it BEFORE it penetrates the foundation.  Any other solution won't get the crawl space dry.

Here are the steps I recommend you take, assuming they haven't been done already:

1) excavate around the entire foundation to expose it all the way down to the bottom of the footer.
2) apply a quality waterproofing system to the wall and footer - not dampproofing, but waterproofing, and preferably a proprietary system like Tuf-N-Dry or Rub-R-Wal if they're available in your area.  Make sure a protection board is installed over the membrane
3) install a washed gravel base around the footer, as deep as the footer and about a foot wide
4) install a sleeved, perforated plastic drain tile around the entire footer.
5) if possible, drain the tile to the lake - this may not be possible if the water level is as high as it looks in your photos.  Or connect the tile to an internal sump pump with a battery backup that drains to the lake
6) cover the tile with washed gravel almost to grade - leave the last 6 inches for topsoil.  The gravel should completely surround the foundation for about 2 feet from the foundation wall.

The point here is to surround the foundation with a drainage channel that will collect groundwater before it contacts the foundation and drain it away through a tile system.  Once the water's in the crawl space it's much harder to deal with.

Lastly, you should talk with your builder; assuming he's built in the area before, he probably should have informed you about the high water table and insisted that proper measures be taken to prevent water infiltration.  This can't have been a total suprise to anyone - except maybe you!  What about your neighbors - do they have similar problems?

I'm curious about your comments regarding where to pump the water - it seems like the obvious solution is to pump it back into the lake.  Am I missing something here?

Hope this helps!

Richard Taylor, AIA
Richard Taylor Architects, LLC
www.rtastudio.com
www.betterhomedesign.blogspot.com