Drainage Tile and Foundation Membrane

One item I haven’t written about is waterproofing our foundation walls and preventing water problems in the basement. As a kid growing up, we lived in a house with a basement that became a shallow pond at one end during prolonged rains. The only thing missing was the stocked trout. It was a nightmare! For our current project we used drainage tile and foundation membrane to waterproof our off grid ICF home.

Johanna Working Around the Foundation

Johanna Working Around the Foundation

As you probably remember, we had a large hole excavated and then I set the footings in. For this part of Nova Scotia, our footings needed to be 4 feet down to get below worst case frost line. Once the concrete footings were poured, we started building the ICF walls. The walls were poured, the floor framing was built and then at that point, we were getting close to back filling around the walls.

Keep in mind, it was critical to build the floor because it acted as an internal brace against the force of backfilled dirt. Without the floor framing, if we backfilled, we potentially could have deformed or caved in a wall from the pressure of all the dirt and rock.

Water Proof Membrane Application

But before we could backfill, we needed to do some waterproofing. Nudura has a waterproof membrane that comes on a roll. I believe it is a 4 foot wide roll. There is a summer and winter weight. All that means is the sticky backing differs depending on the temperature when the material is applied so that good adherence to the foam exterior is achieved.

With a brush, we carefully cleaned the exterior of the ICF foam to give the sticky backing the best bonding surface. First the membrane was cut into appropriate lengths as determined by the height of the wall below grade. Starting at a corner, we peeled the backing off and started to apply the membrane vertically to the exterior wall. We overlapped the footing a few inches so that any water that might come down the wall will run off the footing.

Water Proof Membrane Below Grade

Water Proof Membrane Below Grade

Application of the membrane is a job for at least 2 people It’s best if one person mans the top of the piece while the other is peeling and applying as you work your way down the wall. Each successive piece was overlapped at the seam by about 4 inches. This was done all the way around the perimeter of the building.

Dimpled Plastic Protective Cover

Then we bought a dimpled plastic protective cover that also came on a roll and applied that on top of the waterproof membrane. Its purpose is to protect the membrane from jagged rocks when the back filling is done. There are fasteners that need to be purchased just for attaching the dimpled material. The fasteners keep the dimple board in position for back filling. 

Dimple Board Protecting Membrane on Wall

Dimple Board Protecting Membrane on Wall

At the top of the dimple board, there is a plastic strip that is screwed on to make a tight seam at the top. That also supports the dimple board while the trench around the house is backfilled.

I would definitely consider using this water proofing material on any below ground structure. Not only ICF, but poured foundations and cinder block.

Weeping Tile Installation

Once the waterproofing was done it was time to install the weeping tile. Kind of a weird name. There are a couple of options here and we chose to use 4 inch perforated pvc sewer pipe. The perforations face down and any water that accumulates around the foundation will seep into the pipe to be transported away from the house.

Covering Pipe with Clean Stone

Covering Pipe with Clean Stone

There is also a flexible hose that can be used but we heard there is potential for the pipe to collapse so we went with rigid pipe.

We laid a layer of clean gravel around the foundation as a bed and then plumbed the drainage pipes in. The pipes were placed at a slight angle so that all water in the pipes would run to a central point where a “T’ was plumbed in. At the “T”, solid pipe was connected and with the aid of a transit, a long trench was dug, pipe laid, and ultimately plumbed to where it would drain freely a long ways from the house. In our case, several hundred feet away.

Determining Pipe Elevation with Transit

Determining Pipe Elevation with Transit

The last thing we did to ensure a water free basement is to have the outside properly graded to drain water away from the house. Because we have a hip roof all the way around, water flows off the roof on 4 sides. Grading is critical to make sure water isn’t funneled towards the house.

As an added measure, because we had extra plastic dimple board. I had the excavator dig a flat area along the house. That flat area was about 4 feet wide which is the same width as the dimple board. I laid the dimple board flat with a slight angle away from the house and then we backfilled over it, essentially creating a water barrier from the house four feet out. That will also help keep water from percolating down to the footings.

Until next time, keep the dream alive! We wish you a great day!

Ron and Johanna

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