View Full Version : Horizontal reinforcement for basement foundation walls

April 6th, 2011, 17:22
I never noticed it before but Table R404.1.1(5) does not give the horizontal reinforcement for concrete foundation walls... only vertical.

But every engineered wall will note both horizontal and vertical.

And so I spent today building an easy-to-use spreadsheet that will calculate the minimum steel reinforcement for grade beams and trench footing based on the book, "Simplified Engineering for Architects & Engineers".

The results are consistent with the IRC table for plain concrete (no reinforcement necessary).

Is there anything out there that would justify and/or help calculate the minimum size and spacing for horizontal rebar?


ICC Certified Building Plan Examiner

Mark K
April 6th, 2011, 18:14
The IBC references ACI 318 which in turn sets minimum reinforcement spacing and ratios. Specifically ACI 318 Sections 7.6 & 7.12.

April 6th, 2011, 18:44
Horizontal for UN-Supported concrete walls is here

R404.1.2.2 Reinforcement for foundation walls. Concrete foundation walls shall be laterally supported at the
top and bottom.
Horizontal reinforcement shall be provided in accordance with Table R404.1.2(1). ......
That table only adresses UNSUPPORTED Walls

April 6th, 2011, 18:55
Engineers will typically put in steel for temperature and shrinkage. For 60 ksi reinforcement, the minimum area of steel is equal to 0.0018 x the gross area of the wall for temp and shrinkage reinforcement.

April 7th, 2011, 08:16
Check out footnote l on table r404.1.1(5). You gotta read the fine print.

rktect 1
April 7th, 2011, 10:01
I point this out a lot on plans to look at footnote (l) as well as footenote (g).

(l) makes a lot of upset people, usually because they haden't noticed they needed any vert. rebar but (g) sometimes gets them happy once again.

April 7th, 2011, 10:21
Daywalker and rktect,
You must be using 2012 IRC or some Chicago Mafia/Union code. I could not find a fifth table R404.1.1(5). Is this something provided by your local amendments?

Mark K,
According to ACI 318, 7.6.5; The practical minimum for my grade beams is to have HORIZONTAL rebar spaced no more than 18 inches on center. Otherwise, we would be talking about a concrete wall thickness less than 6 inches ... and we will never see that.
Phil & Mark,
As for ACI, 7.12; I appreciate this minimum to control shrinkage when my calculations for required area of steel to resist tension is nearly zero.

Table R404.1.2(1); This is great. Considering that I see most cast-in-place basement walls poured at 9 ft. tall or more, I will always expect to see at least one #4 bar top, one in the middle, one near the bottom. But I do not know how this jives with ACI 318, 7.6.5 which appears to have a minimum of 18 inches on center.

Originally I was only concerned with grade beams that were either 36 or 42 inches deep. But now I realize that these can be plain concrete unless subject to unusual or extreme loads. As a result of this study, I get the idea that horizontal reinforcement for foundations is never a major concern. Three #4 bar should always do the trick.

Thanks everyone.


rktect 1
April 7th, 2011, 10:39
I'm using standard IRC 2006 table 404.1.1(5)

You were the one who referenced 404.1.1(5) originally.

What are you using?

April 7th, 2011, 11:01
Oops, IRC Table 404.1.1(5) is easily found in the hard copy but not the online version. That's weird.

rktect 1
April 21st, 2011, 15:32
I feel like I am the only plans examiner enforcing this section.

Everytime I mention vertical rebar, contractors and architects go nuts.

Anybody else actually writing reviews with vert. rebar notes?

April 21st, 2011, 21:48
Sometimes 10" poured walls can have no rebar at all. Go figure. I think that the 2009 has more stringent requirements but I just got my copy yesterday and have not really jumped in yet.

April 22nd, 2011, 06:47
I get rebar specified frequently. Usually verticals with (2) #4 within 12" of the top of the wall.

9' wall with 8' of unbalanced backfill can be 8" thick without reinforcing if you use 4000psi.

April 22nd, 2011, 08:30
Vertical re-bar.......standard procedure around here. Been enforcing it for about the last 2 years, ever since we adopted the international 2006 codes.
I do the plan review and the inspections. Took alot of effort on my part to educate the concrete guys. The cry from the wilderness was loud.

rktect 1
April 22nd, 2011, 10:01
I get rebar specified frequently. Usually verticals with (2) #4 within 12" of the top of the wall.

9' wall with 8' of unbalanced backfill can be 8" thick without reinforcing if you use 4000psi.

Only if you have the right soil. Around here we don't have a lot of GW,GP, SW or SP. Even though the architects tell me it is so, the soils report does not.

Take a look at table 405.1.

April 22nd, 2011, 13:51
rktect.. true that, I am blessed with GW.

No soil type was specified.. so it cannot be said that every wall requires reinforcing.

I'm familiar with the table ;)