30 Years Later – Fixing Those Drainage Problems

Or so I thought. Let me explain.

When I moved into the 1780s house there was a hill on the west side that channeled runoff right into the dry-stone foundation. During rainstorms rivulets of water would flow into the basement with abandon. The house had only survived so long because the soil is very sandy. Moisture that got into the basement would quickly soak into the ground and disappear.

Step one was to change the topography. I hired an excavation contractor to move several hundred yards of earth from the west side of the house, creating a bit of a swale to direct runoff away from the house.

Step two was to dig a deep trench about three feet from the house to try to intercept the water flowing toward the foundation. I couldn’t dig that trench right against the foundation, because we have a rubble foundation that is vertical on the interior but sloping away from the house on the exterior.

I dug the trench by hand to the depth of the basement floor (I was thirty years younger back then and full of energy), then created a sloped plane where I could install two inches of extruded polystyrene insulation and a plastic moisture barrier. I wanted not only to deal with drainage, but also to insulate the basement while I was at it.

I installed perforated drainage tile at the bottom of the trench, backfilled with crushed stone, dealt with the tricky detailing at the window wells, and finished it off. Water flows off the roof eaves and is directed away from the house….

At least that was the plan.

But with heavy rains, I discovered that my drainage layer didn’t work at the window wells. Water somehow made its way around the plastic and into the basement—carrying the sandy soil with it.

Fifteen years later, I tried a fix—hiring a builder this time (I had less of that youthful energy by then) to expose the top of the trench and install a layer of EPDM rubber mat. Again, we dealt with the tricky detail at the window well….

And again, we failed. Moisture still came into the basement and still carried the sandy soil with it. We ended up with a sinkhole in our lawn. The folds around the window wells just didn’t work.

That brought us to this summer. We’re wanting to fix up the house so that we can put it on the market in the next year or so as we move to the farm we bought down the road, and I knew that I would finally have to fix these drainage problems before selling the house.

Working with a different builder, my friend Eli Gould, we decided to eliminate the windows altogether so that the drainage could be continuous from the wall system down to the sloped insulation. Building scientist friends of mine, Terry Brennan and Andy Shapiro, were staying at our house one night when we were thinking about this solution, and they concurred that eliminating those windows was a no-brainer.

We now know that basement windows shouldn’t be used for ventilation in our climate—because they introduce more moisture than they remove. Yes, we will lose some natural light, but that’s not a big deal since we don’t use the basement for anything besides our heating system, indirect hot water tank, pressure tank for water, freezer, and some limited storage.

So here we are. Done. The walls have four layers of drainage, lapped so that water can’t sneak in. We use a house wrap, Grace Ice & Water Shield, EPDM, and metal flashing (for protection on the outside). We installed an additional length of drainage tile, and more crushed stone. We replaced some rotted clapboards at the bottom of the wall. I think it’s going to work like a charm!

What we have created is essentially an underground roof (a name given to this approach by building scientist Bill Rose). Water comes off the eaves of the roof and hits the crushed stone, dropping down and being carried away by the drainage layers and drainage tile. The sloped insulation saves some energy and keeps the basement from freezing.

Looking good so far!

Do you have similar drainage problems? Check out our GreenSpec guide to help you find foundation and slab drainage products.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.