How often do you guys waterproof the inside of a crawl space space?
Our builder is installing a french drain on the OUTSIDE of the foundation, as well as a new drain in the yard itself.
A friend of a friend who owns a waterproofing company suggested that the inside of the space should get a drainage system as well.
Do crawl spaces often flood? Is this necessary?
TIA
Replies
I live in a semi-desert area, less than 12" precip annually, so my comments need to be compared to the local conditions where you are. Code here permits waterproofing exterior of foundation (tar seal or similar) and then 2" slush coat concrete on crawl space floor. Then perimeter drain around exterior of footing and leading away from structure. Roof drainage merely required to directed away from building. Many buildings drain to surface only, not even a dry well let alone connect to storm sewer.
Your block foundation would be a greater risk of water permeating through than with concrete foundation. I think on consideration for the small extra cost that a crawl space floor drain would be a good thing. Hopefully there is enough fall in the existing house drainage system and there would be no need for a sump and pump.
If the exterior drain is done well, the interior drain is redundant.
As Sly suggested it depends a lot on how much water you are getting and the existing drainage. When you talk about water it is not just rain fall per annum but you also have to consider things like water table, roof run-off, grade of the lot and other factors as well.
The friend of a friend is in the business of waterproofing so just bear in mind that his opinion may be a little on the bias side.
Depends on your location. Some only require outside and some only require the inside but some are a pain and require both. Just as long as it is installed properly and you do a good job with filtering to prevent the sediment from getting into the system, it should do its job. Also, I make sure that there is a capillary break between the soil and the concrete to prevent any wicking.
I forgot to mention that you should have gutters installed as soon as possible to prevent roof runoff around the foundation. Check the code in your area but I run corrugated drains from the gutters underground and to the streets storm sewers if grade allows. It is amazing how much rain is dumped next to the foundation from the roof. This also results in a much dryer basement.
Edited 10/6/2004 1:43 pm ET by CrackerJacks