Hi All,
We are in the beginning stages of planning to build a house in the Lakes Region of New Hampshire. I would like to put in a full basement to use as a workshop, finished to some extent and full of tools, of course, if I can be sure that it will stay dry. The area typically has a high water table. When we had the perc test done for our septic design in the spring of 2001 the engineer hit water at about 18″. That was an extremely and unusually wet spring and I’m not sure where the water table normally sits, but I have to assume the water would often rise above the level of a basement floor.
Because of the high water table, we have to place the septic above grade, in a mound about 4 feet high. I plan to use extra fill between the house and the septic to create a level yard, which means my house will be about 4 feet higher than it normally would be, but the basement floor will still end up at least 4 feet below grade. Because the lot is small, I can’t put the septic system far enough away from the house to allow the use of foundation drains. Furthermore, the lot is almost perfectly flat, dropping by less than five feet from back to front, so there would be nowhere to drain the water to.
Is there a reliable way to waterproof a basement under these conditions? “Plan B” would be to build a separate “garage-like” structure for the shop, but I am trying to avoid that extra, considerable expense.
Thanks for your advice!
Norm
Replies
without drains and a sump system I am at a loss to come up with a way to do it. Maybe someone else???????
Phil,
Thanks, that sounds like something that could work. To make sure I have the details straight, you had 4" perf around the inside of the foundation and a couple of lines across the middle, all in gravel below the basement slab, leading to a corner where you had a sump pump. You also sloped the basement floor to collect water in the corner where the sump pump was in case the water got in.
Did you have a floor installed? I'm imagining you could put pressure treated strapping with plastic sheeting over it, with a subfloor on top of that, allowing water that gets in to run in the space under the plastic to the corner where the pump is.
Did you pump the water up to that pipe that was through the foundation 18" below grade? And could you tell me what peel and stick exterior foundation waterproofing is? I'm not familiar with that. Thanks a lot!
Norm
Norm,
Your description is correct. I did not have a floor over the concrete. The water which got in once was from a (guess) 25 year rain storm and we got about 4 inches of water. Didn't really create a problem because the pump kept up with it and in 12 hours, it was all gone. Yes, I pumped the water directly into the vertical pipe up the inside of the wall then through the fdn below grade. The benefit of this system is that you can attach extended plastic pipe outside the fdn to reach the extremedies of your lot before discharging the water. The completed system doesn't have to be part of your final inspection!! Mine wasn't either. My terrain was very similar to yours, including septic. Although we sold the house some years age for a much larger one, the system still works perfectly. We are in the same town.
Phil
"I can't put the septic system far enough away from the house to allow the use of foundation drains."
No foundation drains, no basement. I wouldn't even consider it.
There's no such thing as nonexistence.
Now that I reread my last response, the drainage system described by Phil is still a foundation drainage system that probably would not be allowed by the limitations on my septic design. I was leaning toward's Boss Hog's position originally, and may end up staying with that, unless anyone else has a clever idea.
Norm