I’m trying out a new excavator next week (new to me, that is) on a small addition. However, he surprised me by saying that he doesn’t use filter fabric for the drainage pipes. He says that instead of the fines clogging the pipe, they will now just clog the fabric, so what’s the use of it? I didn’t have a good answer for him… I checked past posts, and while a few people have brought the subject up, I could find no real discussion of it.
Any thoughts???
Thanks, –Brian
Discover a concrete-free foundation option that doesn't require any digging.
"I have learned so much thanks to the searchable articles on the FHB website. I can confidently say that I expect to be a life-long subscriber." - M.K.
Dig into cutting-edge approaches and decades of proven solutions with total access to our experts and tradespeople.
Start Free Trial NowGet instant access to the latest developments in green building, research, and reports from the field.
Start Free Trial Now
Replies
At least if the fabric clogs it would shed water away from the basement wall rather than having it pool up around the clogged perforated pipe.
Where are you located? What are other builders doing in your area?
j
I'm in northern Vermont. Lots of clay around here. I mostly do small remodels, so I'm not that familiar with what goes on around here in the foundation department. Nevertheless, I took fabric to be standard practice, --but I suppose that comes more from reading books and magazines than a close knowledge of local practice.Brian
Filter fabric is a real PITA to install, especially if your excavator is used to working in very stable soils where you can get away with a steep-walled excavation right next to the foundation wall. If he's used to flopping his perforated pipe in, dumping some crushed rock in over top of it, and backfilling without getting out of the cab having to lay filter fabric down in the muck will make him grumpy. I'd check out a few other builders in your area to see what common practice is before letting him leave it out. Last thing you want is to find out you should have done it 6 months from now. j
It may mean that this guy doesn't like to bother with it.
I did one a few years ago without the sock on the tile, but did use filter fabric over the crushed stone. I also had two sides that I had a stacked arrangemnt of drain tile. One at the footing line and one half way up the foundation wall. I tied them both together with a wye and exited to daylight on don the hill. I cvered the whole shebang of tile and stone with filter fabric and backfilled it. It works great.
You could purchase the drain tile with the sock already on it and hewould but it in. Or, you let him install his corner cutting way and then you add the fabric over the stone before the backfill.
I had a foundation guy tell me he wouldn't use Form-A-Drain because it "just silted up anyway." I ask how he put in standard drain tiles. He always used tile with the sock over it, but considered placing fabric over the form-a-drain a waste of time. He didn't do my footings, I did, and they also work as advertised.
Maybe he is lazy
Maybe he is trying to create extra future work for himself
or Maybe he has a valid concern.
Lot of guys here don't like to put a sock directly on the pipe for that reason, but prefer to use fabric outside of the stone itself. i'm not sure from your description if he wants NO fabric at all.
Old way of filtering the fines is to lay a couple inches of hay around the stone which we still do sometimes where it is easier to get it in than to work with fabric.
Welcome to the
Taunton University of Knowledge FHB Campus at Breaktime.
where ...
Excellence is its own reward!
It seems to me that even if you accepted his reasoning that the filter cloth could get clogged over time, there is still no downside to installing it. It is still going to be a barrier against fines washing through the gravel and migrating towards the drain tile. As long as the gravel is sloped away from the house, this "barrier" will still help to accomplish the goal of helping to keep the drain tile from clogging.
In some cases I am a fan of overkill (particularly where the cost of the overkill is a tiny tiny fraction of the cost of resolving an issue later). I could see the reasoning in being concerned about a sock covered drain tile getting clogged especially with fine clay-like soils. So why not do both? The sock gets protected by the gravel covered with filter cloth. The extra cost of using a sock covered tile would be a total non-issue.
I worked with a guy last summer who did use sock-covered drain tile, covered that with a good amount of gravel, followed by just regular fill. I always had the feeling that this was not the "best" way of doing it because I probably would have added the additional barrier of cloth above the gravel, ..... but his way did satisfy the building inspector.
"this "barrier" will still help to accomplish the goal of helping to keep the drain tile from clogging."Yes - enough water present to have the sort of hydraulic pressure to leak through the foundation wall, would push it thru the filter fabric first, even if coated with fines.
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
Anyone have a preferred brand of filter fabric, size, or type? I've done some searching and the products vary quite a bit. The big thing is woven vs. non-woven. And I'd like to get the biggest size I can.
My experience with the non-woven fabric thus far has been marginal. That is you need to be carefull how you handle it and in back filling because it pulls apart easily.
Have not used the woven fabric.
It does sound better.
Thanks for everyone's replies. My client and I decided this morning to ask our excavator to use fabric.Brian
Ideally the fabirc should be installed at the outside of the crushed rock. The water velocity is typically low enough out that far, that the fines can't be carried by the water, plus there is a lot more area to clog.
Use woven to the lining the trench to the top & then install gravel & pipe wrap fabric over & cover w/ what ever sand gravel. It will last years.
I just bought a home in Southern VT. Had foundation drainage installed 3 years ago. 2 weeks after closing had seepage, opened the trench, pipe clogged solid, Guess what - plenty of gravel but- filled w/ dirt NO FABRIC.
Do it right the first time!