# Pilaster use in cast in place walls



## Jay (Feb 6, 2019)

General question:  How many of you design a projecting pilaster into cast in place walls?

My experience has been that they are sometimes needed and sometimes can be accomplished as an integral pilaster (flush with wall) via additional steel reinforcement.  Years back with CMU walls they would always be included per design loads and also Building Code requirements.  Have a current job whereby I have a long and deep basement wall alongside what will be a very active driveway.  Mason bid the plans and is now installing form work.  Of course, now he decides to alert homeowner that the two pilasters I have in the plans are not needed.  Mason claims the pilaster is doing absolutely nothing structurally.  I think he's just being lazy and trying to get to the next job.  Thoughts appreciated.


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## classicT (Feb 6, 2019)

Can you please clarify, is this cast-in place concrete or is it grouted masonry?

Pilasters are not near as common in cast-in place concrete walls as they are in grouted masonry. Either way, would definitely be dependent upon the overturning forces at top of wall and reinforcement within.


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## RLGA (Feb 6, 2019)

I think the structural engineer may have a difference of opinion, if it was designed by a structural engineer.


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## khsmith55 (Feb 6, 2019)

Agree with Ron the pilaster may or may not have been used as a design element. Simple solution, have the Mason "over stamp" the Engineers drawing deleting the pilasters, oh and get a copy of the Masons E&O Policy too.


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## Mark K (Feb 6, 2019)

There are several issues here.

It is inappropriate for the contractor to state that a structural element is not needed.  One might even ask if he is practicing engineering while not being licensed.  From a contractual perspective it would be appropriate to say build as per the approved construction documents.

You might ask the contractor how much money he will give back to the owner if the pilaster is not needed.  Is the potential savings enough to justify the additional engineering costs and the process of submitting the revised documents to the city for approval.  Will this have an impact on project schedule?

While walls can often be designed to accommodate large point loads this is something that the structural engineer would need to consider


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## Mark K (Feb 6, 2019)

The mason cannot overstamp the engineers drawings unless he is a licensed engineer or architect and unless the project owner wishes to replace the engineer and have the mason take responsibility for the whole project.  What does the general contractor have to say about this.


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## khsmith55 (Feb 6, 2019)

Mark, was being cynical.


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## Jay (Feb 6, 2019)

Ty, sorry for my lack of info.  This is cast in place reinforced concrete foundation wall for a new residence.  I added one single pilaster on a 40 foot long wall which also acts as bearing for a drop beam, along with beam pocket.   

Mark, good point!  I often ask contractors in these situations why they didn't bring things like this up earlier when they were bidding the job.  It's always the day it is supposed to be installed, that a question arises.  And indeed, the contractors never offer a credit, it needs to be requested.  Imagine that?


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## Msradell (Feb 6, 2019)

I don't believe I've seen a Pilaster in a residential job in over 5 years. A couple may have had a short section with additional reinforcing that's even very rare. I just finished with 1 that back wall of the basement 80' long x 12' tall and it didn't even have any additional reinforcing.. I don't even regularly see them in commercial applications except if the walls are CMU instead of poured.


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## RLGA (Feb 6, 2019)

If you designed it, and they bid on it as designed and signed the contract, then enforce the contract. If the contractor wants to change things to make it easier for them, then ask for a credit. If they won't offer one, then tell them to build it as indicated on the contract documents--no further discussion.


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## classicT (Feb 7, 2019)

Jay said:


> Ty, sorry for my lack of info.  This is cast in place reinforced concrete foundation wall for a new residence.  I added one single pilaster on a 40 foot long wall which also acts as bearing for a drop beam, along with beam pocket.
> 
> Mark, good point!  I often ask contractors in these situations why they didn't bring things like this up earlier when they were bidding the job.  It's always the day it is supposed to be installed, that a question arises.  And indeed, the contractors never offer a credit, it needs to be requested.  Imagine that?


Ok, on the same page.

Most likely, the crew has typical wall panels and lacks the appropriate forms to pour pilasters. This means that they have to cut and build new forms, which detracts from their wall form inventory.

Due to the high compressive strength of concrete, pilasters are not typically required for concrete, especially when one considers that the load disperses at a 45-degree angle. This means that a point load on a 10-ft tall wall is dispersed over approximately 20-ft of footing line (given no openings). While this can be a beneficial property of cast-in-place concrete, if the designer does not want the load spread along a footing line, a pilaster and isolated footing may be desirable.

Ultimately, as many have said, the contractor is responsible to build to the design. Failure to follow the design should not be permitted unless the design is re-performed at their expense.


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## ADAguy (Feb 8, 2019)

Consider the use of the pilasters as he has indicated: beam support, possible surcharge, weight of vehicles, etc.
Lastly, if he bid it he bought it, No? This a GC or CM project or by owner?


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## tmurray (Feb 8, 2019)

Mark K said:


> The mason cannot overstamp the engineers drawings unless he is a licensed engineer or architect and unless the project owner wishes to replace the engineer and have the mason take responsibility for the whole project.


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## ADAguy (Feb 11, 2019)

That would be a "righto"


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## Jay (Feb 11, 2019)

Mason is building per the plans.  This is a spec house for a builder.  I have done about 6 homes with this builder and have had some pilasters in previous designs with no questions.  

As far as I am concerned, the pilaster may very well be not needed if you really get down to the nitty gritty, but the codes as we know are a minimum standard.  I once witnesses a backhoe driver moving his rig very close to a poured foundation wall.  They backfilled without any floor deck or supports (not my project) and I saw the backhoe driver hit the foundation wall.  Guess what happened....? the wall moved a bit.  I can't help but wonder if a pilaster could have helped stabilize that wall?  That scenario has always been stuck in my head.


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## Mark K (Feb 11, 2019)

I doubt that a pilaster would have had a significant impact on the damage induced by the backhoe.


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## Jay (Feb 11, 2019)

Would have to be a very large pilaster!


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