Follow-up to Best backfill materials to keep new perimeter drain clean
This is a follow-up to (post #205744), which I just replied to with these questions.
I’ve decided I should have started a new post. Sorry for the duplication.
I’m doing a perimeter drain exactly what the original poster is doing. I was planning to: (a) lay 6′ wide filter fabric in the trench and pin it to the outside dirt wall, (b) add 3″ of gravel, (c) lay the drain pipe, (d) add 18″ of gravel, (e) wrap the filter fabric around the gravel, (f) add surplus masonry sand over the filter fabric, and (g) add about 3′ of clay backfill, and (h) add about 1′ of top soil.
The problem is the masonry sand is very fine. (My mason didn’t like it because it was so fine, he said it was for brick.) Would it be worse than clay?
Also, I was surprised to read recommendations to add gravel all the way to the top. Is that commonly done? That would be a lot of gravel. (My trench is 3′ wide).
Replies
It would have been fine there in the other thread.
Especially if you think it's the same question.................
I answered there.
Best of luck with your project.
Hire a Geotechnical Engineer
I recommend that you hire a Getechnical Engineering firm, to do the design of the drainage system. They are more complex than most folks think, and a well engineered design will give you a system that works, with out being oversized.
They will have the knowledge, and equipment to test the existing soils, to see how easily the fines will transport materials and water.
If your system drains to daylight put a coarse gravel mound at the outlet to keep snakes and rodents out. Also, put a couple of clean outs at the high end of your system so you can flush out any sediments that do get into your drain pipe.