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nickfinity
Registered Users
Posts:7
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| 02/21/2008 12:12 PM |
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| Hello,
My wife and I are (finally) finishing up our plans. We're going to have use ICF for our basement and first floor walls. According to our architect and installer we can go with 6" all the way. Is there any benefit to going with 8" block instead?
For some reason I had my mind set on the idea of using 8" block. It would be a bit more expensive than just the additional concrete cost (although it would require a bit less rebar, but not much) because apparently the 6" block comes from a different plant than the 8" block and shipping cost is more.
I guess I'm just trying to feel comfortable with the decision to go with 6" after having set my mind (whether I should have or not) on 8" block.
Thanks,
Nick |
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renangle
Registered Users
Posts:91
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| 02/21/2008 12:29 PM |
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Nick,
You inquiry sounds somewhat familiar, I am curious as to the location of your job...our manufacture (and others) make block in different locations. To answer your question, if you architect says you are fine with 6" all the way, then I wouldn't really give it a second thought. We have done 6" all the way up, 8" to 6", and 8" all the way up. I would say that it really comes down to peace of mind, if you feel more comfortable spending (ca. $2000.00) to feel comfortable for the next 10 years spend it.
I hope you enjoy the new home.
renangle |
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walltech
Registered Users
Posts:469
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| 02/23/2008 7:37 AM |
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Nick, here in Michigan we use 6" 100% of the time above grade for 1 and 2 story homes. Bucking 8" is a little more difficult due to the 13" lumber needed unless doing v-buck or inside bucks. Also jambing the 13" wall will be more expensive, but that deep well may be what your looking for.
Dave |
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nickfinity
Registered Users
Posts:7
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| 02/23/2008 11:59 PM |
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renangle - Thanks for the info - and I sent you an email (through this site).
Dave - Thanks for the help. The deep well would be nice, but I'm not sure it's worth the extra money. We're going to get it priced out both ways, but I'd be surprised now if we went with the 8". |
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OKBlocker
Registered Users
Posts:635
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| 02/24/2008 12:14 AM |
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| We use nothing but 8" in Oklahoma now. Too much backfill pressure for 6". All 8" wall with #5 rebar on 16" centers horizontally and 12" on center vertically. Long walls have "dead men" built in. Contact me for more info. |
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nickfinity
Registered Users
Posts:7
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| 02/25/2008 10:13 PM |
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How much backfill do you feel comfortable going with when you are using 6" walls? Our land slopes down so the basement isn't completely backfilled.
Thanks,
Nick
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Ian with ICF Builders
Posts:0
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| 02/26/2008 2:41 PM |
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| Why not just have the basement engineered by an engineer that is familar with the soils etc. and can design the basement walls accordingly rather than "guessing" on something that is one of the most important parts of the house? For what it is worth, engineering is cheap insurance especially if you are not sure which way to go. I would be VERY HESITANT to take the free advice of the installers here as GOSPEL especially since very few people that post here have any formal education with regards to foundation design, soil analysis, structural concrete or any other professional training relating to design or engineering of structures. |
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Th.E.
Registered Users
Posts:7
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| 03/01/2008 1:07 PM |
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| 8" is the minimum thickness for proper structural design. Even if you are not in a seismic region it is still advisable (although some optimization may be possible). The rebars should be properly designed and detailed by an engineer. The details provided by the ICF material providers are insufficient. |
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walltech
Registered Users
Posts:469
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| 03/02/2008 8:57 AM |
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Th.E. : As I read your post it appears your saying that "Prescriptive Methods Two" is a insufficient document. Why would professional engineers such as the team of P.E.'s who contributed too PM2 endorse such a document along with the NAHB, Portland cement and numerous ICF related manufactures if it was so insufficient?
I understand that PM2 doesn't meet the requirements of ACI 318-06 which you are bound too by your engineers stamp,
but tens of thousands of homes are built too PM2 with much success. I'm surely not stating that Nickfinity should build with 6", just that its common here in Mi and Nick should do his diligence locally and see what other ICF projects are using, and work with his local ICF supplier along with the BI as too whether he needs engineering.
The.E. give us your thoughts on PM2.
Dave
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southwind
Registered Users
Posts:7
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| 03/02/2008 9:38 AM |
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| We never used 6" below grade. Remember an architect is not an engineer and my thoughts on below grade applications is that there is no substitute for mass. |
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Th.E.
Registered Users
Posts:7
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| 03/02/2008 12:01 PM |
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"southwind" makes a valid argument. To clarify a bit, mass is good, but "mass concrete" is not; proper reinforcement is also required.
Concrete has only 1/10 of its compressive strength in tension, given that there are no cracks (even hairline cracks). When a wall is laterally loaded (like in a basement due to earth pressure) then tensile stresses develop. A single line of reinforcement, in the middle (as per many ICF manufacturers), is not adequate in the design of retaining walls. Proper rebar detailing to resist compressive loads, is also very limited to non-existent by most ICF material manufacturers/providers.
In regard to "Prescriptive Methods 2" one should be very careful on its intended use and therefore its limitations. "Introduction" and "1.3 Scope" tries to clarify these.
By the way "nickfinity", for a basement use a solid type of ICF wall. |
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