should fabric be used on interior drains
plate
| Posted in Construction Techniques on
I have read various opinions and it seems that with Exterior french drain a filter fabric is a good idea. Is this true for Interior french drains?
The french drain leads to a sump pump, the soil is largely clay. I have another post asking for fabric recommendations, so I guess I put the cart before the horse on that one.
Any comments are greatly appreciated.
Replies
Are the interior drains going to be installed in crushed stone? If so, you should be fine without the fabric. The fabric is there to keep silt out of the pipe. No silt, no need for fabric. It's best to ask for washed stone, because it has less silt on it.
If you're setting the drain directly in clay you're going to have other problems.
I was planning on washed crushed stone below (1-2")and on top of the Perforated pvc pipe (2").
I dug down about 12 inches (depth and width) adjacent to interior basement wall. I don't get a lot of water (after fixing gutters and downspouts), but I plan on finishing the basement so I wanted the insurance of the french drain/sump pump.
I suppose that there isn't much erosion happening because the water trickles in as opposed to outside where the flow could be much greater.
If you don't get much water the fabric may be overkill. It certainly isn't bad insurance though. I'd probably line the trench with it before backfilling with stone.
100' of fabric is less than 15 bucks... I'd use it.http://www.tvwsolar.com
We'll have a kid
Or maybe we'll rent one
He's got to be straight
We don't want a bent one
He'll drink his baby brew
From a big brass cup
Someday he may be president
If things loosen up
Have you ever had problems with filter fabric becoming clogged with silt and acting as a dam? Several times when I have removed old fabric it appeared to be largely impermeable. I've never worried about it in exterior perimeter situations because it would just keep the water away from the foundation, but I wonder if fines in the surrounding soil might do this in an interior situation and cause the drain to be less effective.
I have seen landscape fabric used as filter fabric do that. I use a soil seperator fabric that is used in lateral field installations. It is thinner and has no weave in the fabric so it is less prone to glogging.
I ordered a 4 foot wide roll of DeWitt Filter Fabric (deWitt Company), from "forestry suppliers inc" website, it is non woven and needle punched. It should arrive next week sometime.
I have a somewhat unusual situation perhaps. A 90-100 yr old stone foundation (not unusual) which at one time they added an additional 1 foot wide stone wall in front of it, inside the basement.
Since the trench is now dug (no stone or anything in it yet), I could observe how the water makes it in. At one corner of the trench, I saw water trickling in that actually caused the clay to "melt" a small portion of the trench wall and cause the clay to flow down to the bottom of the trench.
This "melting" of the clay convinced me it would be a good idea to use the filter fabric. I know it would have taken years to clog the drain pipe, but if the filter fabric won't hurt then perhaps I will extend the longevity of the french drain. It was hard work, I would hate to do it again anytime soon. Thanks for all the comments.
Edited 7/24/2009 11:11 am ET by plate
Edited 7/24/2009 11:14 am ET by plate
Here are a couple demonstrating some of what Mike said. Two interior and one exterior
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Thanks for the pictures!
What kind of fabric is that in the exterior picture?
A landscape fabric. We get different widths and weights, so I'm not sure which that is.There was stone surronding the drain pipe with fabric under it, then some hay over that, then the fabric, and a bit more stone weighting it in place. We used the hay on that one because it was mid-winter and we had to protect the footers from frost getting under for a while. Used curring blankets on and off during the process until backfill time.No fabric inside, like Mike mentioned, but we ran poly VB over the stone and under the slab.BTW, that perf pipe for drainage interior not only led to daylight for drainage, but had a gooseneck to vent outside above for passive radon venting
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I just got to wondering if you meant the fabric in the bottom, or the dimplematt with fabric attached for drainage plane on the wall itself?
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No, I ment the fabric in the bottom of the trench.
I recognized the dimplematt on the wall.
I remember when you first posted pictures of that job.
Picked up some valuable information from that thread.
Most folks around here use the continuous black pipe that come in a big roll. It already has a silt sock on the pipe. We use it inside and out. Doesn't make sense to have two different materials on the job for any small extra cost for the sock. Fine material has a way of working it's way along with water, seems like a no brainer. You aren't going to be able to go back and add it later.
Beat it to fit / Paint it to match
Apparently the filter socks are worthless. Inspections here will not pass any drain system with just a sock, they've had too many complaints about clogged ones.http://www.tvwsolar.com
We'll have a kid
Or maybe we'll rent one
He's got to be straight
We don't want a bent one
He'll drink his baby brew
From a big brass cup
Someday he may be president
If things loosen up
and that elephant trunk won't take very much compression or a large rock point loading it.
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!