Online Blog > Previous Entry 4/10/2015 > 5/01/2015 - Concrete Foundation Construction - dampproofing and french drains > Next Entry 6/9/2015
We have two major spring project starts - one is a large shop with an apartment in Clark Fork, while the other is a custom home in Careywood. In order to achieve economies of scale, we decided to stay right on excavation and foundation work and get them both done and ready for framing, even though we will then have to frame and finish them in sequence since we only run one crew plus our subcontractors.
The following photos show the asphalt emulsion coat, which is just
dampproofing the foundation. We like to keep all wood and siding materials
at least 10" above finished grade, and we bring the damp proofing to this
line on the concrete. We then place a perforated 4" PVC pipe around
the base of the footer and run the pipe our to daylight. We place washed
drain rock on top of the pipe and cover that with a landscape fabric before
we place the topsoil. This fabric will help keep dirt out of the pipe and
keep it flowing free of debris.
In this first photo, we have an extra large center pad as part of the continuous footer because this will be a major load bearing point for the ridge beam, and the roof, when loaded with snow, is designed to transfer 25,000 pounds of live load to that part of the foundation.
In the following photo, note that we do not backfill the foundation until we have built the subfloor. That is so that the lateral pressure of the backfill against the foundation will be resisted by the subfloor (which connects a wall to the opposing wall). Failure to do this can result in bent and bowed concrete walls, especially those that are not at a full cure (design load strength of concrete takes 28 days curing time).
I'll also call attention to the number of foundation vents. If you are going to vent a foundation, you have to do so adequately, otherwise you are creating more of a problem than a solution. The number of vents here exceeds code, which usually only specifies 1 SQF per 1500 SQF when a 6 mil vapor retarder is used, but the same code desires 100 square inches per 150 SQF when no vapor retarder is used.