Our house is in western Washington and during the winter we get a lot water in the crawl space. I'd like to tackle installing a drainage system – probably with a sump pump – and then encapsulate the crawl space to warm up the floors above and control moisture from the crawl space.
I'm thinking that the approach would be to install a drain around the perimeter of the crawl space that runs back to a sump (or sumps) and pump from there. I think my idea is similar to How should I install a curtain drain in my crawl space? and the follow ups Curtain drain in the crawl space - Part 2 and Curtain drain in the crawl space - Part 3. But I have a few questions about the design, details, and materials:
First is a design question, assuming that there isn't obvious evidence of a spring will a drain around the perimeter catch most or all of the water intrusion?
How far away from the stem walls should I keep the trench for the drain?
Is a "perforated drain pipe with sock" like this product from Home Depot a good choice for the drain or would I do better with one of the "drainage systems" that seem to the rage with the crawl space encapsulation specialists?
Assuming that the pipe and sock is the right material, is there a rule of thumb for how large the trench should be?
The pipe seems pretty flexible, so I'm wondering about keeping a constant grade. Do I want to do something like lay down a bed of sand and slope that to ensure drainage? Or is an overall pitch all I need?
Would there be any reason not to use the material excavated from the trench to fill in low areas in the crawl space? I was thinking of trying to create either a flat floor or a gentle crown in the center.
Is there anything else I should be thinking about?
