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Architects engineer changed rebar spacing in foundation walls from 40" OC to 35" OC could it stay at 40" or larger?

Peterp

Peterp

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Joined
Mar 19, 2023
Messages
4
Location
Long Island
Hello

I'm building a single family home on Long Island NY with an 8' basement and no issue with soil in area.
Our foundation and rebar was originally the following on the plans see below... Note the 40" OC for #6 rebar.
The architect asked an engineer to review their plans and they changed the spacing to 35" O.C... Is this overkill what is the code for rebar spacing? For anyone who's building in NYS or North East what did your foundations call for with rebar gauge and spacing?

8" POURED CONCRETE FOUNDATION WALL W/ #6 REBAR @ 40" O.C. VERTICALLY & #4 REBAR @ TOP, BOTTOM, & 1/3 POINTS HORIZONTALLY ON 10"x20" CONTINUOUS FOOTING W/ (3) #4 BARS, SEE SECTION/DETAIL

Thanks
 
Is your interest in using the least required? If you want the protection of the architects insurance, don't bother. It won't be worth your time.

It probably is overkill, but very, very small cost compared to whole house.
 
Actually, 35" is a lot wider spacing than we normally see around here. I just saw the plan for a house where the Vert Bars were #5 Bars at 18" and the Horz Bars were the same. As the reviews posters have mentioned if that's what the engineer specified that's what you should go with, there is no standard spacing for rebar.
 
Peterp said:
Is there no maximum spacing code per gauge of rebar?
Click to expand...
I'm not much help as we don't do basements here in California. I used to build them in Colorado but that was so long ago that I don't recall the details. I can tell you that every time that I have built something for myself, I beefed up on the engineer's plans. That's because engineers seem to find a place between failure and just past success. So I would place the #6 at 24"oc with #4 horizontals at 16"oc.

Call it shrinkage crack control if you like. There would be two bars at the top and two bars at the bottom and the footing steel would be doubled.

Our resident gadfly engineer would disagree. "After all a licensed engineer has determined a perfectly acceptable plan."
 
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If the owner of the project has concerns they should talk with their engineer. If the owner has lost faith in their engineer they can hire another engineer. But if they go this route use care in selecting an engineer with a good reputation.. If the concern is to minimize project cost it may cost more money to save on the cost of the reinforcing.

Without detailed knowledge of the project it is not possible to make statements regarding what the code would require.

I am used to seeing smaller bars closer together but if we are talking about retaining walls in the basement you could see more reinforcement.

Unless the building department wants to accept the liability associated with this project the building department should respect the engineer's decision as long as it is more than the minimum required by the code.
 
To the OP... most of what is said above is an opinion. The one person who has the requisite experience and familiarity with your project to determine the sufficient amount of reinforcement, is your engineer. Follow his/her plans. If you don't think they are correct, either talk to them or hire a new engineer to review/redesign.
 
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Peterp said:
The architect asked an engineer to review their plans and they changed the spacing to 35" O.C.
Click to expand...
Nothing wrong with the Architect asking an engineer for a peer review of the plans. I commend the architect for doing this, it is an indication that you have a good one. There are a lot of factors that go into the design of a foundation wall. What is the height of the wall, unbalanced backfill, is it supported on the top and bottom from lateral movement, will it be subject to hydrostatic pressures, is the wall supporting light frame construction or concrete construction, what is the length of the wall?

Maybe the engineer changed the rebar spacing based on the soil classifications as required by the code. Maybe the arch wasn't sure what the soil classification for you site was when he did the drawings and therefore asked the engineer for the review.
Perhaps if you ask the Architect or engineer why the change, they will provide you with a simple explanation.


1679330637540.png
 
I don't think anyone here will second guess an engineer and/or architect. If you were building it yourself, I might have looked at the New York Residential Code, available online, as an extra check for you.

You should ask for an explanation, so you know why. Asking for a second opinion from another engineer or architect would likely cost more than any possible savings, so not recommended.

Lots of houses built without architects and engineers. On the other hand, design professionals usually bring much value to a building, often along with some very conservative above minimum choices. I personally wish all houses had architects involved, and commend you for having one.

There's near unanimity in responses here, which is very rare.
 
Engineer's can and will specify items greater than what the code requires where circumstances dictate they must. Unless you get a new approved plan set, follow the engineering you have.
 
Hey all thanks for the replies, to be clear we already built this house and did follow the plans and engineer. I was curious more about why they'd choose that size rebar / spacing. I'm currently planning another new construction and will get another engineers advice if the rebar is similar.

Another builders plans in the area had no rebar called for in their walls so the builder asked their mason to add it but didn't know the size or spacing and the town had approved those plans. They did have rebar called for in their footing but not the walls
 
Table R404.1.1-2 is for masonry block foundations. Your original post stated a poured concrete foundation wall which would be Table 404.1.2(3) that I posted above. Yes, the table states the spacing # 6 @ 41" OC based on the SP soils you have would be the minimum you are required to do.
Remember the codes are a minimum requirement or put another way the worst building you can legally build.

Your arch may have used the code and the engineer may have used one of 3 other permitted design manuals to arrive at the spacing he is requiring.
R404.1.3 Concrete foundation walls.
Concrete foundation walls that support light-frame walls shall be designed and constructed in accordance with the provisions of this section, ACI 318, ACI 332 or PCA 100.

What are you questioning and why?
 
The reality is there might not have been any rebar required in accordance with the code. However, the engineer might have specified some based on their professional discretion related to local conditions, expected level of performance, building geometry, etc.

There is no guarantee that the rebar schedule for this house is suitable for any other.
 
TABLE R404.1.2(8)
MINIMUM VERTICAL REINFORCEMENT FOR 6-, 8-, 10- AND 12-INCH NOMINAL FLAT BASEMENT WALLS b, c, d, e, f, h, i, k, n, o

m. A plain concrete wall with a minimum nominal thickness of 12 inches is permitted, provided that the minimum specified compressive strength of concrete, f ¢c, is 3,500 psi.
 
We're the plans submitted to the AHJ and approved @ 40-inches O/C or is this pre-submittal, planning stage?
 
Peterp said:
Another builders plans in the area had no rebar called for in their walls so the builder asked their mason to add it but didn't know the size or spacing and the town had approved those plans. They did have rebar called for in their footing but not the walls
Click to expand...
I have only seen one foundation without rebar, a 4-ft tall foundation without rebar and it was cracked so bad in several places and the walls where so out of plumb. This foundation was poured without inspection and was present prior to my arrival at that municipality. I was asked later by a guy that purchased the abandoned property if they were to get an engineer involved to rectify the issue could they build on the walls? He determined that the cost of engineering was going to be more than removing the foundation walls and starting anew. One or two crack repair solutions might have worked but this foundation looked like counsin eddie's grill.
 
Msradell said:
Actually, 35" is a lot wider spacing than we normally see around here. I just saw the plan for a house where the Vert Bars were #5 Bars at 18" and the Horz Bars were the same. As the reviews posters have mentioned if that's what the engineer specified that's what you should go with, there is no standard spacing for rebar.
Click to expand...

We installed rebar at 32" OC on a recent engineered 12' tall CMU wall on a single story small commercial structure in the pacific NW in a high seismic zone. It all depends on the engineering...
 
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