Backfilling

The foundation finally got backfilled last week, during the three day heat wave where the temperature got up to around 90. Even though most of the work was done by the excavator, we still had to do a lot of exhausting manual labor to lay down various pipes and move crushed stone around.

Before any of this work could be done, we had a coating specialist come out and seal the below-grade part of the foundation with a sticky black rubberized tar substance, on top of which was placed a 2-inch thick compressed fiberglass matting that acts as a drainage board.

Then we laid down the perimeter French drain pipe next to the foundation footings. These are four inch wide plastic pipes with holes on the side facing down. These pipes go all the way around the foundation and exit at one runout pipe. They had to be joined to the basement floor drain pipe, using a rather complicated set of joints. We had originally planned to put a second set of French drain pipes on top of the footings, but drainage board left no room for that.

Then we had to lay down water pipes from the spring. This was tedious work that involved making a bed of dirt under the easily damaged black poly pipes, then piling six inches more dirt on top of the pipes to protect them from the stones that were going to be placed on top of them.

Finally the excavator could do the first part of his work, adding an amazing amount of crushed stone (because of the very wet location) up against the foundation. On top of this we laid down some filter fabric, which supposedly prevents silt from running down into the stone and clogging the French drain pipes. Then the excavator came back and finished the job by filling with dirt. Finally we were able get to the deck of the first floor without climbing ladders.

There is some controversy, we discovered, about the idea of backfilling before the decking is in place, which we had originally wanted to do to make building easier. But both our foundation contractor and excavator were opposed to the idea, saying that without any kind of bracing (such as that provided by the beams plus decking), the concrete foundation walls could collapse inward. We went along with their recommendation, but there was one problem with it, aside from the inconvenience of having to use ladders for so long: the decking was now vulnerable to the coating and backfilling operations. We neglected to tarp the decking for these operations, and as a result, some stones and black tarry spray landed on the deck, and one bit of the deck was gouged by the excavator’s machinery. I think (and FirstDay Cottage recommends this) that a better way to do this job would have been to brace the foundation, perhaps using cut tree trunks, and backfill before doing any of the work on the house. Even the way we did it, with the backfill happening late, we still had to use one tree trunk brace at one point, and it wouldn’t have been much more work to make two more braces.