Waterproofing |

By Ben James on August 27, 2013

The only thing that likes basements more than spiders is water. While spiders may be beneficial in a basement, water is not. Our architect, Stefan came up with an interesting way of keeping the water out.

We are using a product called Delta PT, which is designed for use in mines. That’s right, mines. In fact, when I called the sales representative he asked, “Okay, you’re in Fairbanks, Alaska, right? Which mining outfit do you work for?” I guess the Fairbank Construction name threw him off, since he actually sells to a number of mining companies in Fairbanks, Alaska.

Delta PT is a dimpled drainage mat that lays against the concrete and channels water to a desired location. In our case, the water will drain into the floor drainage pipe and be collected in a sump, where it will be pumped up and out into the city sewer.

The biggest challenge we faced was the ceiling in the Music Room. The ceiling is actually the underside of the sidewalk! So it’s easy to see how water could seep down through the concrete and drip down the ceiling. The drainage mat had to be installed in big, continuous sheets that go from the ceiling, down the wall, and into the floor drainage pipe. It was a pain in the neck! Literally. Installing that drain mat over your head actually hurts your neck. There was a lot of grumbling when we were installing the drain mat on the ceiling.

: The waterproofing drain mat is installed on top of the foundation wall…

: …and the ceiling.

: The drain mat is tacked in place using a gunpowder-actuated nail gun. A special, insanely sticky tape is used to seal the nails.

: Wood batts are shot into the concrete to hold the drain mat in place, and create a guide for the spray foam insulation.

: Yep, gotta do the ceiling too. That ceiling is actually the underside of the sidewalk.

: Only a couple more to go!

: Delta PT installed in an actual mine shaft. Usually plaster or concrete is sprayed right on top of the drain mat.

: Insulation is sprayed right on top of the drain mat. The installers will often scrape the insulation flat to the wood to allow for the instalation of wall board, etc. We are building a second wall next to the foundation wall, so we just left the insulation rough to get a little extra insulation value and save on labor.