Filter Fabric Disagreement on French Drain…

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Speede541

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To cut to the quick, my concrete guy and my foundation guy have a difference of opinion on wrapping a sub-surface drain in filter fabric (gravel and all, not a "pipe sock").

My concrete guy's been working these types of jobs for longer than I care to imagine, and he's the one who gets called back if something goes wrong. In my case, it's a 4' x 30' CMU wall with sloppy wet soil piled high on one side. I hired him because I trust him and he has great local references, but...

My foundation guy (who's long out of the picture now, but I worked with him closely on the dozens of feet of pipe comprising the 4 sub-surface drains surrounding our foundation) did the whole filter fabric wrapping the gravel bit. He's a high-priced guy, also highly recommended, well respected and competent.

I understand the arguments for both, but side with my foundation guy, with my concrete guy firmly believing that the filter will get coated in muck and effectively shunning water off to the sides, away from the gravel base. He pulled up a section of dirt- and root-infested fabric to make his case. He's not *refusing* to do it my way, but strongly, strongly opinionated on the matter.

Now, in reality, we're talking just 30 feet of drain pipe with a cleanout. I honestly trust my concrete guy, and figure that the worst case scenario is me having to run a hose through there to flush the thing out if it gets caked up.

Do any of you feel very, very strongly on the full filter fabric wrap -- enough so that I should insist on it being put in?
 

LLigetfa

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Without the filter fabric, the fines will migrate to the stone and you will have clogged up stone and poor draining. Ideally, if you can layer the gradient, going from course to fine in sucessive layers, you could get away without filter cloth, but that is a lot of work, and a lot of material. I suggest you use the filter fabric but then put a layer of coarse builders sand over it. The idea is not to have an attractive growth medium where roots want to migrate to. None the less, the roots will eventually win anyway.
 

Speede541

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Thanks for your input, and for the sand idea.

Out of curiosity, is addressed anywhere in code?
 
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