Help With Drainage Issue??

kdub1777

Hello, I am trying to brainstorm on a drainage issue we are going to have on a project we are finishing up.

We have two multi-family buildings that will sit 12' from each other. (Stemwalls are 12' apart at the sideyard) Side yards are 40' long.

Because of the terrain, one of the 'top of foundations' is 6" lower than the other foundation. This leaves us with a problem when backfilling up to 6" from the top of foundations and getting our grade we need away from the foundation. The main concern, (and I think it will happen) is the drain off from the higher foundation will all drain towards the lower foundation and cause us all sorts of problems, even with some sort of V pan grading. We are trying to be proactive here.

The length/depth of the side yards is 40' long and 12' wide between the buildings.


A couple ideas I were bouncing around today:

1: build a small retaining wall to account for the (2) different grades from the foundations. How to build this retaining wall??

2. Put in some sort of drain, french drain, etc.. What sort of drain??

3. Pour a concrete slab covering the whole side yards, doweled into the stemwalls, that drains to front and rear yards. But how would we control the runoff at the front and rear yards off of the slab in a bad rain storm?? We don't want potential erosion where it comes off the slab and meets soil.

Let me know what you think or if you guys can come up with anything else that might work.


Thanks in advance

kdub1777

Oops. I posted this in the wrong forum. Can I get some help in moving it to the General Discussion Forum??

Tim Garrison PE

I suggest a good footing drain at the lower foundation. I typically spec Mira-Drain. Or you could use a 12" +/- drain rock (usually 3/4" leach field rock) layer from bottom of footing to top of grade with a 4" perf pipe at the bottom. The trick is to make sure the bottom of either system is just below the level of the footing. That way it will intercept all water, both surface and subsurface.