Replies

1. 
   Jon_R | Aug 22, 2019 03:48pm | #1

   I used 6 mil LDPE with no foam but with pea gravel and drainpipe at the outer edge. Works well and IMO, should be far more common.

1. 
   KevinEJ | Aug 22, 2019 04:47pm | #2

   Jon,
   Your LDPE is unprotected underneath (sitting on soil and buried)?
   Does your drainpipe all connect and daylight somewhere? Based on these articles, I've gathered that the drainpipe is optional if soil drains well (my sandy soil does). I'm considering leaving that aspect out.

1. 
   Jon_R | Aug 22, 2019 04:59pm | #3

   Yes and yes. I have clay soil with more porous soil against the foundation - so I need to get the water well away from the wall.

   With sandy soil I'm not sure you need an underground roof at all.

2. 
   STEPHEN SHEEHY | Aug 23, 2019 02:29pm | #8

   We have really sandy, well drained soils. Nevertheless, we installed underground gutter system that runs to daylight, as well as the typical perimeter drain, also running to daylight.
   No matter how hard it rains, I've never seen a drop of water coming out of the pipes. I guess we could have skipped the drains.

1. 
   KevinEJ | Aug 23, 2019 02:33pm | #9

   Stephen, what climate zone? Does the ground freeze in winters? Mine does, which I assume affects soils ability to drain.

1. 
   STEPHEN SHEEHY | Aug 23, 2019 03:20pm | #10

   Kevin: We're in Maine, zone 6, so the ground certainly freezes.

2. Expert Member
   BILL WICHERS | Aug 23, 2019 07:31pm | #11

   Better to have it and not need it than to need it and not have it :-)

   I'd say you built in some insurance against water problems. I wish I had more of that at my own house.

   Bill

2. Expert Member
   BILL WICHERS | Aug 22, 2019 05:09pm | #4

   Any-PE (PE = Polyethylene) that is black should last a long time, at least 20-30 years, as long as it's thick enough to handle physical abuse. MDPE (Medium Density PE) with black pigment is what is used for the outer sheath of outdoor telephone and fiber optic cables and it is rated for 20-30 years in direct sunlight exposure. HDPE is commonly used for underground ducts. The black pigment is what gives you UV protection so that is important.

   You might try calling some plastics supply houses. Many can do limited fabrication. If you ordered some black LDPE (or HDPE, which will be harder and stiffer) sheet, maybe 1/16" thick, you could have them form it into troughs. Troughs can then be welded together with a plastic welder to make longer sections. You can't glue polyethylene, but you could screw the sections together if you don't want to deal with a plastic welder.

   Bill

1. 
   KevinEJ | Aug 22, 2019 05:45pm | #5

   Bill,
   How important is UV protection, since these systems are buried? I will have enough extra 10mil white poly from my crawlspace to do the in-ground gutters.
   (this stuff: https://www.americover.com/product/pro-crawl-barrier/)

   Would that be a bad idea to use here?

2. 
   KevinEJ | Aug 22, 2019 05:54pm | #6

   Bill,
   The system I'm putting in doesn't resemble a trough, so the custom fabrication seems excessive. It's more of a pitched roof like this illustration.
   How important is UV protection or the color black, since these systems are buried underground? I will have enough white 10mil poly vapor barrier leftover from my crawlspace project. Would that be a bad idea to use here?

   
1. Expert Member
   BILL WICHERS | Aug 22, 2019 06:10pm | #7

   Ah, I was thinking you were making an "in-ground gutter" to catch runoff from the roof.

   In your case, with the plastic sheet buried a foot deep, you'd probably be OK with the white material. It's primarily the UV in sunlight that degrades plastic outdoors, so if you're buried deep enough that you won't be inadvertently exposing the plastic you should be OK without the black UV-stabilized stuff.

   Bill