Rebar spacing in ICF foundation walls
Gene_Davis
| Posted in Construction Techniques on
We are planning the layout, and my first thought is to go 18″ centers for vertical, and 16″ centers horizontally (one per block course). All bar is #4. Verts need to fall on 6″ modularity.
The crete core in the walls is 6″ thickness.
This, for a seven course high (9′-4″) foundation with gravelly loam soil conditions, 4000 psf bearing capacity, with one storey wood frame construction above.
What have you done?
Edited 3/10/2007 12:59 pm ET by Gene_Davis
Replies
GeneDavis,
I don't have my assembly instruction in front of me for ICF's so whatever I say, do what the instructions suggest and ignore me..
Having said that it sounds correct.. I tend towards the over kill and I used two on my horizontal plus I wire tied everything together..
at the very top run two bar hort with the corners bend and not lapped
For sandy loam like that you probably don't need as much as that, but it is a tall wall and steel is not all that expensive so go for it.
Have you read my comments and methods in the Jack this house John Henry thread?
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Gene - from your question, it sounds like you haven't seen the prescriptive manual for ICF construction - have you?
It is available free online, HUD puts it out - it has rebar spacing charts for all types of soil and building type, and LOTS more. Its 140 pages or so. If you cannot find it in a google search, email me and I'll send you the PDF.
http://www.google.com/search?q=HUD+%2B+rebar+%2B+ICF+%2B+PDF&start=0&ie=utf-8&oe=utf-8&client=firefox-a&rls=org.mozilla:en-US:officialI'm interested too, if you could identify which link is correct. PDFs are a big usse of bandwidth and ram for me so I don't want to sample too many to find out.or - email me
[email protected]
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Go here. http://www.pathnet.org/sp.asp?id=1014
It's a big download, but good info. 200 pages.
It shows, as I thought, that horizontal bar is doing so little, structurally, that you need very little. A number 4 in the bottom, one at the top, and at third points is sufficient, just about no matter what.
These guys that are saying I need two bars at the top must have shares in Nucor and USSteel. One run at about 12" down from the top will do just fine.
But, as logic would dictate, basement wall height and most particularly, unbalanced load coming from backfill, dictates the verts.
You also need to understand the equivalent fluid density of the soil you have for backfill. What we will deal with on our sites is the type that results in the lowest category of fluid density.
Because our foundation is a walkout, with unbalanced backfill heights varying, we will go high density (12" centers) where we have almost-buried walls, and reduce down to 48" spacings where the walls poke most of the way out.
two bars at top to tie the wall together, and because its code.
I cannot find the code language. The AHJ performs no inspections whatsoever, which is neither here nor there, but the code used here is the New York State Building Code.
Can you cite me the language that governs your installations, please, and the code from which it comes?
The manufacturer's instructions say nothing about it. They do say, however, that we are advised to fasten a continuous waler to the top edge of the forms, to maintain line. We'll do that for sure. We'll also use 2-1/2" steel track to cap the formwall top edges, to give us a nice smooth strike-off surface.
Where else are you placing your horizontal resteel, besides the two bars at form tops?
Piffin - did the link from Gene get you to the manual?
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Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
brownie right about the twins at top, but for others - place them closer top interior than exterior
Welcome to the
Taunton University of Knowledge FHB Campus at Breaktime.
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Gene :
In the installers manual, you are about to recieve, there are Engineered backfill
tables based on the lateral loading of the walls.
The tables are designed around the intended backfill height (your choice) and a soil density of 30 lbs per cubic foot.(drained) Usually.
You will be able to design your rebar requirements and spacings from these tables.
Except for the Lintels,of course. Tables for them too.
Standard bar lap is 40 x's bar diameter. Contact splicing is allowable. No tying.
Backfill with respect after your floor deck is on.
Another tip, one 3/4 in bar equals two 1/2 in bars ( your #4 i think). Over crowding the 6in wall cavity with bars can make consolidation difficult.
Using a bigger bar is always best.
Edited 3/10/2007 7:50 pm ET by ericicf
Edited 3/10/2007 9:15 pm ET by ericicf
When plans are submitted based on the Prescriptive Design Requirements handbook put out by ARXX the city sometimes increases the rebar significantly. Usually it's a structure in an alley, but sometimes it's just "because".
One particular nearby city treats all ICF's the same so one like ARXX with an open center very nearly the same as a wall built with forms is overbuilt quit a bit. #5 12" oc. vert and #4 16" oc horz. is not unheard of for a 9' wall, especially for a 2 story.
Beer was created so carpenters wouldn't rule the world.