Poly vs EPDM for perimeter “french drain
Stray
| Posted in Construction Techniques on
Nothin’ is forevever.
That said, I’m wondering what to line the bottom of a perimeter foundation drain with to get the most longevity.
I’m planning a 24″ wide “french” drain around 3/4ths of my house foundation, with drain pipe and round stone back fill. I plan to line the sloped trench with some form of waterproof membrane. My immediate thoughts was heavy mil poly or EPDM.
I’m guessing EPDM would be longer-lived, but is obviously more expensive.
If neither are exposed to UV, should I still expect much better lifetime from EPDM? or is Poly (doubled or trippled up) just as good?
Any thoughts appreciated!
Replies
"That said, I'm wondering what to line the bottom of a perimeter foundation drain with to get the most longevity.
I'm planning a 24" wide "French" drain"
Uhhmmm... You're talking about two different things there.
A Perimeter foundation drain, AKA Footing drain, is a drain tile wrapped in gravel wrapped in filter fabric. It sets on or next to the Tee footing.
A french drain is a gravel filled ditch, sometimes covered with filter fabric and sod.
2 layers of 6 mil visqueen lining a french drain should last as long as it needs to, (payback on EPDM would be in the hundreds of years,) as long as you don't have soft soil under it and large jagged stone on top of it. 3/4 Drain gravel will work great.
SamT
Yeah, when I re-read my original post I wondered if that would be confusing.
In actuality, a french drain around your foundation IS a perimeter foundation drain (with no mention of footers, or elevation). I certainly could have worded it better....
I do like the visqueen idea for the toughness.
"In actuality, a french drain around your foundation IS a perimeter foundation drain (with no mention of footers, or elevation)."Do you mean a french drain just outside the footing, before you backfill?SamT
A french drain is not a perimeter drain. It is a half azzed substitute for a failing drainage system, usually palkced near the surface.You do not want a waterproof membrane surronding your stone and drain pipe. You need to let the water get to the drain, not keep it away. A lot of ground water rises up to the drain as well as wicking down to it.
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"It is a half azzed substitute for a failing drainage system"
Agreed. If I had the $, It would be better to dig up my entire foundation and re-do the footer drain, parging, drain mat, etc... Not in the cards right now, and frankly the only time I have concerns about water intrusion is if the gutters are clogged or overwhlemed. I'm really just trying to capture surface water during a storm and divert it away.
re: the water perking up from below and into a drain: the site has got some good slope and the water table is well below my basement slab.
It's very common here (upstate NY) to see details calling for a clay or bentonite layer on the surface around the foundation, to shed water out and away from the house. I presume this would also keep water from perking upward, like you and Jeff describe. In this case I was thinking I could get the same effect with plastic sheeting of some form or another.
Here's a sketch of what I was considering. The sheeting is open at the lowest point (by drain pipe). I certainly don't want to create a bathtub.
View Image
Edited 9/18/2007 10:44 am ET by Stray
I see. At first, it sopunded like you were doing a perimeter drain and calling it a French drain. Since htis is a surface stop-gap it is an actual french drain situation. The liner might do you some good then.The holes do always go at 4 and 8 o:clock, never at two and ten o:clock
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
either on the bottom or the whole way around!
Jeff Buck Construction
Artistry In Carpentry
Pittsburgh Pa
I guess visqueen is the ticket?
I guess visqueen is the ticket?
6 mil, several layers, is all we use over our underground houses. Extended out 20' from the perimeter. No waterproofing needed on the walls or roof. Perimeter drains never have any water coming out. Oldest poly is upwards of 2 decades, no sign of deterioration. Ground water/soil here is acidic. PAHS Designer/Builder- Bury it!
Looks like a modified french drain - nothing wrong w/a barrier between the foundation and the water you're wanting to divert but the filter fabric, drain rock and properly laid perforated pipe are still needed. One thing I didn't see in your drawing is a clean-out. A properly angled clean-out saves you from digging up the system and reinstalling after a few years.
You may consider increasing that 24" dimension to 8 or 10 feet. Also don't install the 2x curb. My Dad had a similar configuration, but without the all important drain tile, and it acted as a tub. I'm doing the same thing. I've had 6-mil white poly on the ground, exposed for about a year now with little, if any deterioration. I'll either replace it or add another layer before filling with sand and laying a brick patio. Any day now....
SamT,
I haven't kept up on the topic of soils acids eating 6 mil. plastic sheeting. I know that some years ago around here we were told not to put the 6 ,mil. in direct burial situations because the acid would cause it to deteriorate rapidly. Any input on that? Just curious if you or anyone else has any info on the topic."Poor is not the person who has too little, but the person who craves more."...Seneca
Well I hadn't considered any acidity issues!
Is visqueen just as suseptable (ie is it just reinforced poly, or something else)?
Gosh, I don't know. I'm originally from a high alkaline area. It seemed to last forever there. Here in central MO, it's also a bit alkaline.Vinegar, muriatic, and sulfuric acids all come in plastic bottles, for what that's worth.I found this: http://www.dep.state.pa.us/dep/deputate/airwaste/wm/RECYCLE/FACTS/AUTOBAT.htm
Acid-resistant curbing should be constructed around the storage area to contain any spills that escape the building. Curbs for small storage areas could be constructed of either asphalt or a simple wooden frame completely covered with a 20-40 mil sheet of acid-resistant polyethylene, polypropylene, or polyvinyl chloride.SamT
Edited 9/18/2007 11:31 am by SamT
I just started some work and I've been pulling buried visqueen out and there is no deteriation at all. And the soil here is acidic. This visqueen has been there for maybe ( I'm guessing) 10-15 years.
when a french drain is laid using the "half perforated" pipe ...
the holes go on the bottom.
so the water can "push up" from below ... and flow out.
so U don't want nothing on the bottom of that trench ...
Jeff
Buck Construction
Artistry In Carpentry
Pittsburgh Pa
I always thought the holes went on the bottom so the water wouldn't have to build up 3"-4" before entering the pipe (not necessarily that the water would be perking up from underneath. I suppose in the right situation of soils, that would certainly happen though.
I'm trying to shed stormwater away from my foundation. I don't have issues with standing water or groundwater in this case. See detail on the above post for a visual of what I was planning.
Thanks for your thoughts.
http://www.gardenadvice.co.uk/howto/garden-build/frenchdrain/
Should give you the information you need to construct a true French drain.
Dave