Foundation wall drainage
Chrisroche
| Posted in General Questions on
I am building a house in New Hampshire and just got done having the foundation waterproofed with a liquid waterproofing membrane (which start 8 ft below grade). I will be adding 2 inches of xps on the outside of the foundation and will then be back filling with sand.
I read in a previous article on GBA that you want to have some type of drainage membrane to send water to the foundation drains below. My question is would coarse sand qualify as an acceptable drainage material (I had seen crushed stone mentioned before), or should I install a dimple board of some type. Thanks!
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Replies
Chris,
Coarse sand drains well. It will work (as long as your perforated footing drain pipes are surrounded by crushed stone and wrapped in landscaping fabric to prevent the sand from clogging the pipes).
Remember to install about 6 to 8 inches of clay-rich soil at grade level, above the sand.
Great, this is exactly what I was not sure about. Thank you so much!
Coat the insulation well with a stucco/plaster mix which should extend (at least) 12" below grade. Insects and rodents love to chew into and through this stuff.
We're working on a home built 30 years ago with 5" of stucco'd exterior foam, where the owner thought she had rodents in the house. We dug down a foot below grade and pulled off the lower rows of clapboards and trim to expose the whole area and found dozens of holes used by the critters to provide access to hidden holes in the walls; mostly from enlarging tiny holes in the edges & corners of the stucco. We've added a layer of hardware cloth and stucco'd over that. It's a good reminder to my crew and shows why we abandoned exterior foam and now install it only on the interior. And we save the cost and PIA factor of coating it.
Consider sourcing reclaimed XPS or EPS for your foundation. It will be much cheaper and, at least with the XPS, more environmentally friendly.