Boontucky-girl
Basic Member
Posts:250
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| 12 Aug 2008 09:37 AM |
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I need help settling this question: My husband (and every contractor around here) thinks that the basement and garage slabs need to have these layers:
compacted gravel
poly film
2" of sand
2" of rigid insulation
wiremesh (plus radiant heating)
concrete
I just read the builder's guide to cold climates which says that those 2" of sand can be a moisture trap, and that you don't need to "protect" the poly film.
So, which route is the best to go? Thanks!
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icfcontractor
Basic Member
Posts:277
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| 12 Aug 2008 10:36 AM |
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Boontucky,
If you use a cheap vapor barrier like visqueen then I would agree with the sand. If you use a quality barrier like Stego then I agree with you. Stego in 10 mil is about 50% to 100% more expensive than 6 mil visqueen but you can't hardly tear, rip, or punture the stuff.
ICF Contractor |
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eric monkman
Basic Member
Posts:262
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| 12 Aug 2008 12:09 PM |
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Basement: 6 inches clear stone (minimum),6 mil poly, 2 "rigid foam, mesh, concrete
Garage : Compacted fill, sand or gravel, 6 mil poly, foam, mesh concrete.
You are correct, the sand leveliing bed is an unnecessary PIA...looks good on paper. lol |
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gregj
Basic Member
Posts:326
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| 12 Aug 2008 03:21 PM |
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Well, the sand wouldn't protect the poly since it's between the poly and foam and there's no way the foam is going to damage the poly. The foam will protect the poly during mesh and crete installation.
The only points I can see for the sand is to make leveling easier under the foam and perhaps to speed concrete finishing time in cooler weather, however with the foam in between it may not help much with that.
I really haven't had any problem with holes tears in poly but I don't pour slabs on a daily basis. |
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cmkavala
Veteran Member
Posts:4327
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| 12 Aug 2008 06:56 PM |
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Some building officials require sand under the slab, so that a sharp rock won't work its way up and puncture the poly |
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| Chris Kavala<br>[email protected]<br>1-877-321-SIPS<br /> |
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hausfxr
New Member
Posts:53
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| 12 Aug 2008 07:11 PM |
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I have been involved in the sand or no sand debate many times over the past ten or so years. Here in Portland, OR, the consensus is that sand is not a good idea. While it may provide protection for the VB, it also provides a barrier that can trap water on the wrong side of the VB. That sand layer becomes a reservoir as big as your slab, so water entering from an edge can travel unimpeded to any area, but its best path of least resistence for leaving could be to evaporate up through your slab.
Brint |
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cmkavala
Veteran Member
Posts:4327
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| 12 Aug 2008 07:40 PM |
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Brint; its probably a regional issue, north Geogia requires it, I have seen poly punctures in Pennsylvania from stones moved by frost. All of Florida is sand so it doesn't matter here. Boontucky-girl should check with local building dept. for recommendations |
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| Chris Kavala<br>[email protected]<br>1-877-321-SIPS<br /> |
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wes
Advanced Member
Posts:810
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| 12 Aug 2008 07:42 PM |
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I agree with most others here, sand is not necessary over VB and it could be detriment.
Chris,
I assume the inspectors want the sand to protect the VB from rocks in the concrete?
Would the 2" foam not serve the same purpose? |
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| Wes Shelby<br>Design Systems Group<br>Murray KY<br>[email protected] |
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cmkavala
Veteran Member
Posts:4327
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| 12 Aug 2008 07:49 PM |
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Wes
the details in N. georgia show the sand under the VB in lieu of gravel |
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| Chris Kavala<br>[email protected]<br>1-877-321-SIPS<br /> |
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wes
Advanced Member
Posts:810
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| 12 Aug 2008 07:55 PM |
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Chris,
OK, that makes a lot more sense. |
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| Wes Shelby<br>Design Systems Group<br>Murray KY<br>[email protected] |
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Jelly
Veteran Member
Posts:1017
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| 12 Aug 2008 07:55 PM |
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Great article by Lstiburek regarding sand between the vapor barrier and concrete - he is rabidly against it:
http://www.buildingscience.com/documents/insights/bsi-003-concrete-floor-problems |
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cmkavala
Veteran Member
Posts:4327
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| 12 Aug 2008 08:07 PM |
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jelly;
sand between earth and VB |
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| Chris Kavala<br>[email protected]<br>1-877-321-SIPS<br /> |
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Jelly
Veteran Member
Posts:1017
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| 12 Aug 2008 08:48 PM |
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Right, but Boontucky's order up there puts it on top of the vapor barrier. I suggest any unconvinced party read Lstiburek's article. Of course that probably won't work on a building inspector :( |
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cmkavala
Veteran Member
Posts:4327
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| 13 Aug 2008 05:52 AM |
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I just re-read her post, she said cold climate, is she in cold climate ??
if boontucky is in Kentucky it is a mixed - Humid Climate |
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| Chris Kavala<br>[email protected]<br>1-877-321-SIPS<br /> |
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Boontucky-girl
Basic Member
Posts:250
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| 13 Aug 2008 08:52 AM |
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Yes, I'm right in the smack-dab-middle of Iowa. Someone else thought I was from Boonesville, Ky, but I live in Boone county, IA. Some have declared us Boone residents to be a long lost county of Kentucky, because of our ways, and I actually embrace this. :P
The beauty of my building site is there is no code, and the only inspection on my site will be setbacks and septic, other than that I'm on my own, which can be a blessing, but also a nightmare. If things are done wrong is my fault!
So, for Iowa cold weather climate this should be suitable?
gravel
poly
foam
wiremesh
concrete |
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Alton
Veteran Member
Posts:2164
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| 13 Aug 2008 01:32 PM |
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Boontucky-Girl,
Unless you plan to tie the radiant heat tubes to the wire mesh, why do you plan to use wire mesh? |
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Residential Designer &
Construction Technology Consultant -- E-mail: Alton at Auburn dot Edu Use email format with @ and period .
334 826-3979 |
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Boontucky-girl
Basic Member
Posts:250
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| 13 Aug 2008 02:32 PM |
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I guess I was under the impression that I need reinforcement in my slab. I actually don't know what the flatwork guy will be doing. I think one of the quotes mentioned fiber reinforced concrete, but we haven't decided who will do that yet. The sand argument was with my hubby, and I wanted to reach a decision so that when the flatwork contractor insists on having that sand , we could tell him, no thanks! Kind of hard if one's for it and the other one isn't.
Now, another question is, do I really need the poly if I'm using under slab insulation? |
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Alton
Veteran Member
Posts:2164
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| 13 Aug 2008 04:23 PM |
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Boontucky-Girl,
IMHO:
Reinforcing wire does not add structural strength to the concrete slab. Reinforcing wire is too thin and weak to structurally support a slab. If installed correctly, reinforcing wire is supposed to prevent small cracks from opening up more. However, it is about impossible for the typical residential concrete crew to install reinforcing wire correctly since it has to go in the upper part of the slab. When allowed, I always skip the wire and use fiber mesh. At least the fiber mesh will add some strength to the slab by being throughout the slab.
If you do use fiber mesh, then plan to see the fibers for awhile.
Now if you plan to use radiant heat, then ask someone if you need the wire to hold the radiant tubes in place.
Compacted gravel and a vapor barrier are very important under an indoor concrete slab. The spaces between the compacted gravel will be large enough to stop the upward flow of water by capillary action. Water can flow upward through compacted sand since the spaces are much smaller.
Anyone else have any thoughts about whether to use reinforcing wire and compacted gravel under a basement or garage slab? I try to learn every day. |
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Residential Designer &
Construction Technology Consultant -- E-mail: Alton at Auburn dot Edu Use email format with @ and period .
334 826-3979 |
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gregj
Basic Member
Posts:326
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| 13 Aug 2008 05:33 PM |
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Posted By Boontucky-girl on 08/13/2008 2:32 PM
Now, another question is, do I really need the poly if I'm using under slab insulation? Yes, you really want the poly. The insulation alone won't do it. I saw in your other post you have radon concern. That's another good reason for poly. Are you putting in the infrastructure for radon mitigation in the gravel under the poly and slab so that you can passively or actively vent the radon as needed? Now would be the time to do it. |
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Boontucky-girl
Basic Member
Posts:250
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| 14 Aug 2008 02:46 PM |
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Yes to Poly. Got it. We are scheduled to do forma-drains right now, but I'm looking into monolithic pour the 1rst row of ICF to footing using tyvek (like fast-foot). But have a few concerns that I still need to investigate. If we go this route, we'll have perf pipe for water and radon.
Thanks! |
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