View Full Version : Basement wall thickness
01-14-2004, 05:35 PM
My father in law is building a basement with walls that reach up to 10 - 12 feet in some areas. He was going to use 8 inch hollow block and fill them with concret and rebar. if he uses block should he not use thicker block? would'nt pourd walls be better and if so how thick. the soil around the area is clay. The backfill will probably be around 10 feet is some areas too. Is there a book or web page I can tell him to look. Thanks for the help
Brent, time to consult an architect or engineer. My 42 years of experience tells me that poured concrete would be best. If that is not an option, I would think 12" block , reinforced and filled would be next best way. I am an old carpenter, not a architect or engineer.
01-14-2004, 07:34 PM
The IRC has some prescriptive designs for both poured walls and block ones up to 10' high. The soils that will be used for backfill and the height of backfill are extremely important. The heavier the soil and the taller the backfill, the heavier the needed reinforcing. By the way, the height of the wall is measured from the top of the basement slab, not the top of the footing (unless they happen to be the same--not likely in my area, but...)If the walls are over 10' you will need an engineer if you are using the IRC.
01-14-2004, 07:35 PM
Ditto!! 12in. block or poured concrete are standard issue on basement walls that high around here.FramerT.
Quote¿Sonny 1/14/04 7:34 p.m.
The IRC has some prescriptive designs for both poured walls and block ones up to 10' high. The soils that will be used for backfill and the height of backfill are extremely important. The heavier the soil and the taller the backfill, the heavier the needed reinforcing. By the way, the height of the wall is measured from the top of the basement slab, not the top of the footing (unless they happen to be the same--not likely in my area, but...)If the walls are over 10' you will need an engineer if you are using the IRC."
With all due respect to Sonny,
I will refer to the 2000 IRC, Table R404.1.1(2) Reinforced concrete and masonry foundation walls.
Item e. Unbalanced backfill height is the difference in height of the exterior and interior finish ground levels. Where an interior concrete slab is provided, the unbalanced backfill height shall be measured from the exterior finish ground level to the top of the interior slab.
Also, any wall that exceeds the maximum height of "9" feet are outside the all the parameters of the Tables R404.1.1(1) thru R404.1.1(4).
You would need an engineer's wetstamp to design this.
The IRC is a good reference in my opinion. But, a structural engineer is must. 10 to 12 feet of offset is serious, especially in clay. In my area, 12inch poured walls with plenty of reinforcement would probably be the prescription.
Typically, poured walls go up quicker and finish off better. Lastly, some type of waterproofing system like Koch's TUFF-n-DRI with drainage piping is a must. This with reduce lateral pressure on the foundation and provide a dry basement. I never had a problem in fifteen years building foundations this way. For a few hundred bucks hire an engineer, you'll sleep better.
01-16-2004, 05:34 PM
when (if) you pull permits, the local inspector should be able to tell you what he wants to see and what is required.Plans reviewers in my county sometimes ask for engineer stamps in certain areas depending on the soil.
For my own house with 9' tall walls in some areas I used poured walls and more rebar than usual.
As stated in previous posts,you'll sleep better knowing it is right from the get go.
01-17-2004, 07:43 PM
Hello To all, very good information.
Brent- have you ever considered an Insulating Concrete Form system (I.C.F.'s) for use in this application?
This technology has become the solution for both above & below grade projects, as well as 6 story Condo's, Institutional & Commercial structures.
A very good sourse is the I.C.F.A. web site at
Just an option to consider...
Take care, Sincerely.
I.C.F. North Building Solutions (http://www.icfnorth.com)
01-17-2004, 09:18 PM
bill, With all respect your Building Inspectors should be advising anyone on options offered by the Local Building Code, and not telling you how they want to see it. It's get to see contractor's that are using the IRC on these forums. Later!
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