ELEDSALL
Registered Users
Posts:3
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| 02/07/2008 12:54 PM |
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| I am working on a total ICF design with a sealed crawlspace. The floor height will be 6" above grade. The stem wall/crawlspace specs call for a 18" by 9" footing with two courses of 16" ICF blocks. I can make the 18" clearance between the bottom of my floor trusses and floor of the clawlspace if I do not have to backfill the inside of the footing. In other words, I can use the 9" footing height into my distance requirement. I don't see that the IRC forbids this practice but I haven't seen it done before. Are there any structural, insulation, water, or other issues here? Comments please. |
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cmkavala
Registered Users
Posts:818
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| 02/07/2008 3:35 PM |
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ELEDSALL;
You will need good drainage or your crawlspace could become a swimming pool |
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Chris Kavala
chris@southernsips.com
1-877-321-SIPS |
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robinnc
Registered Users
Posts:115
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| 02/07/2008 11:14 PM |
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The way I understand it is that there has to be a Min. of 18" from the floor of the crawl space and the bottom of the floor joists.
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dmaceld
Registered Users
Posts:494
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| 02/07/2008 11:42 PM |
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Practice probably varies around the country but around here it's done all the time. Faster to excavate a flat bottom hole than a bunch of trenches! I was going to do it but changed my mind. Here's why.
You will want to insulate the footers. You will be circulating air from the crawl space into the living space, therefore the insulation has to have a 15 min thermal barrier over it. This applies to the ICF crawl wall also. You want the crawl space to be dry as possible. If you have a radon issue you need to vent it out. For me this dictates a perf drain pipe all around the interior of the footer with a vent through the roof. The perf pipe needs to have cover to be most effective. The vapor barrier should be above the pipe. Digging down beside the footer is not good practice as you may undermine the soil under the footer.
Taking all these considerations into account I decided it's best to dig a footer trench, put insulation around the footer, put the drain/vent pipe in there, back fill to the top of the footer, put insulation over the entire crawl space area, and pour a rat slab over it. I'm going to put exterior sheet rock, untaped, on the walls. If you don't pour a rat slab, and I'm not saying you should, the biggest issue you will have is making the insulation on footer fire code compliant. You can use Dow Thermax there. Or since the exposed concrete will be fairly minimal take the easy way out and leave it exposed. The backfill will cover the insulation along the side of the footer. Or you could use Dow Thermax to insulate something like 2' wide over the footer and dirt. Put it on top of the vapor barrier.
Now, if you could arrange it such that you could get 24" free space under the floor you'll be a hero. My nephew HVAC man said any time there's at least 24" for a service man to crawl around in, they love the homeowner!!! And they almost cry with joy if there's concrete to move around on!!!!
If you can stand the additional cost consider dropping the footer 8" and using a 1/2 high course of blocks for the first course.
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Building house - what a way to spend retirement! |
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walltech
Registered Users
Posts:469
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| 02/10/2008 10:05 AM |
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Eledsall, why not go slab on foundation instead? It will save allot of money and negate moisture issues. Besides a crawl with no crawl space seems irrelevant.
Dave |
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blackdogarch
Registered Users
Posts:31
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| 02/20/2008 9:55 AM |
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Check the IRC (Residential Code) with your local buildng official.
Footers to frost depth. Verify stable soil at any depth.
18" clearance to soil from bottom of joists. 12" ok if PT joists.
Use plastic or concrete slab for moisture control.
Provide ventilation tot eh crawl space OR access to the basement (see minimum access sizes)
Insulate the floor joists per code (at least) OR if you do the foundation walls, go min 24" below soil level in crawl space. (You are climatizing the crawl space to the house).
Check sections 319.1, N408, N1102.2.2.8 at a minimum.
The above suggestion for deeper access for the poor plumber (and electricians and insulation guys...) is a very good one.
So is the concrete slab if you do not need plumbing access. Just insulate and use a moisture-barrier iunder the slab (8-mill plastic). |
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dmaceld
Registered Users
Posts:494
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| 02/20/2008 3:41 PM |
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Posted By dmaceld on 02/07/2008 11:42 PM
Faster to excavate a flat bottom hole than a bunch of trenches! I was going to do it but changed my mind. Met with my excavator and concrete guys yesterday. We're still going to do a flat bottom hole, pour the footings, and then back fill in between for the drains and slab. Faster and easier than digging trenches they both say.
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Building house - what a way to spend retirement! |
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Cattail Bill
Registered Users
Posts:246
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| 02/20/2008 3:52 PM |
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| Check with your ready mix supplier they have a pourable fill these days that is cheap and gets as hard as concrete. |
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dmaceld
Registered Users
Posts:494
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| 02/20/2008 6:38 PM |
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Posted By Cattail Bill on 02/20/2008 3:52 PM
Check with your ready mix supplier they have a pourable fill these days that is cheap and gets as hard as concrete. Can you give more details? When I was working at the SPR we used to pour a concrete like mix in trenches over pipes to protect them or in the bottom of wet excavations to have a solid surface to work from. I can't for the life of me remember what we called it. Probably the same thing you're talking about. Structurally it ain't worth crap, but gives a solid surface to walk on. Is it a sand mix with low concentration of cement? That should work for a rat slab.
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Building house - what a way to spend retirement! |
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Cattail Bill
Registered Users
Posts:246
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| 02/21/2008 8:11 AM |
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You are correct it is a sand with some portland in it and I do not use it very often, as it is rare to do crawls in Minnesota.
I am not sure it has a name other than pourable fill. |
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Jelly
Registered Users
Posts:274
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| 02/24/2008 11:55 AM |
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Posted By walltech on 02/10/2008 10:05 AM
Eledsall, why not go slab on foundation instead? It will save allot of money and negate moisture issues. Besides a crawl with no crawl space seems irrelevant.
Dave This is what I was wondering. If you're only going to be 6 inches above grade, why not just pour a slab?
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Jelly
Registered Users
Posts:274
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| 02/24/2008 12:03 PM |
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| Mac, I can't picture the method you're talking about. Do you mean you're going to dig a flat bottom hole down as deep as the bottom of the footers? |
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