stlouisz
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Posts:12
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| 07/10/2008 2:18 AM |
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What are the advantages of using 6 inch core vs 4 inch core on the first floor of a home? My architect is interested in using the 4 inch because he feels it will impact the house design less (initially drawn for 2 x 6 construction). Specifically, there are several corners which have short runs because of windows near them. Also, he would like to use 8 inch core for the basement and thus use that as a ledge for the floor joists.
All my research indicates that 6 inch core forms seem to be the most popular, but I'm not sure why. Is there disadvantage to a 4 inch core form? Thanks.
stlouisz
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smartwall
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Posts:57
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| 07/10/2008 8:02 AM |
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| I sell 4 inch for above ground, gives the user more floor space for their buck |
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icfcontractor
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Posts:237
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| 07/10/2008 11:02 AM |
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Stlouisz,
The short answer is most installer find the 6" way easier to work with. When I put my arm inside a 4" form and grab something like a ziptie or piece if rebar, my forearm gets stuck in the block. Then compound that with the seismic requirements in my area and the rebar mat makes it almost impossible to insure a good quality pour.
Setting your joists on the ledge created by the transition from 8 to 6 is a pain and there are way easier and faster way to accomplish the same thing. Although if you use 4", the transition from 8 to 4 would make it easier but still not my preferred method.
Remember you are asking for free advice and opinions on the design and engineering of your home. It brings me back to the old adage, "You get what you pay for."
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Paul Stevens
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Posts:149
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| 07/10/2008 6:58 PM |
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I will usually use 6" all the way to the roof, hang the floor with 2-8" anchors every 16" and away I go. I have also done the method that you are talking about. Depending on which block you decide to use will depend on your rebar spacing, which will have an impact on your pour and consolidation of concrete. Some ICF companies have engineering that requires less rebar than others, (I never quite understood this since 6" of concrete is the same as 6" of concrete regardless of which block it goes in, right?!?) so that would have an impact on you pour and how easy it would go. Also with a 4" block you are only saving 2" of living space, is that really a big difference???
Although I have done a 8" to 4" transition before with success I would probably not do it again due to the ease of a 6", footing to roof truss build.
Paul Stevens |
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SoCalScott
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Posts:41
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| 07/10/2008 11:09 PM |
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I agree with the two posts above on the point that 6" is definitely easier to work with. That being said it comes down to engineering (I know that engineering is not necessary in most parts of the country), but concrete walls 101 tells you that steel placement and size combined with concrete thickness and psi determine loads shear etc.
If your plans aren't engineered I would play it on the safe side and go 6" and use the recommended steel pattern provided by your ICF companie's generic engineering. If you have an engineer and his calcs work out with 4" by all means go for it. But again, the 6" is much easier to work with. Ask your local rep to show you the two forms side by side and you'll see why.
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miformguy
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Posts:27
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| 07/10/2008 11:34 PM |
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When you say "first floor" I assume you are building a single story building on a basement. A lot of people don't like the 11" walls for looks (thick jambs), loss of floor space, and cost..not just concrete but extension jambs. You can use a taper top on your last course of basement and get maximum bearing surface. I prefer to go with 6" all the way but that's what makes this country great...we have options. It comes down to what you like and the installer's comfort level with the product. Thinner walls take more care to insure you don't get voids but will allow for higher slump to help avoid it. Make sure your installer is capable with whatever you decide.
Virgil Schmidt |
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ICFconstruction
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Posts:173
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| 07/11/2008 8:06 PM |
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| Six inch is the way to go. With six inch you can do larger lintel widths. |
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