Maximum amount of stacked blocks on piers?

Can someone point me in the direction of the IRC maximum amount or have a knowledge of how many stacked wood 2x blocks are allowed on concrete block piers to support the main girder system?

For our understanding from framing contractors, a maximum of three 2x blocks are allowed, then metal shims installed after for final leveling.

If we are wrong, we want to know what is right.

Thanks in advanced!

4", or more, concrete (don’t know about steel shims) is required, I believe. I believe that is because one can buy a solid 4" block ready to go, but not for sure on the reasoning.

And, I believe 5 or more blocks, in one pier, need to be core grouted.

Sorry, don’t have the code.

Edit: Try CODES.docx (10.6 KB)

or this:

Codes by state.docx (7.8 KB)

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2018 IRC for the use of CMU’s in piers R606.7.

The “Codes” do not address the use of wood as shims for the very reason you are stating that it can be compressed and cause movements.

Although not “best practice”, those wood 2x’s are never going to compress, so I wouldn’t worry about it.


I agree with Stephen. You might be going a bit overboard. Home inspectors do not do code inspections and you would have to admit nobody is going to do anything about the issue anyway.


I believe there is no fine line between inspecting for defects and performing engineering and whatever this is it ain’t home inspecting as per any SOP.

This is one of those that falls under the what’s acceptable locally. While HUD has some hard rules that limit the total height of the wood blocking and shimming (varies with the area), IRC does not. If you did not notice any depressions from the beam in the 2x blocking, the only way to verify if it’s adequate is to do some math. This falls under engineering. If plans are not available to show this is acceptable, the only way to get this off your back, if you don’t feel comfortable taking on the liability, is to call it out for review by a SE. Remember, unsupported masonry piers are limited in height by IRC. One cannot just stack unlimited number of 2x to support a beam. Ideally, the masonry pier would go up all the way to the bottom of the beam and up to 1inch is filled with a metal shim. But… we don’t live in ideal world, so… The issue here is that someone can come behind you and throw you under the bus, even if nothing happens as a direct result of these four 2x.

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If that is new construction and you are concerned, call your AHJ for a clarification on what he/she will accept. If it is a 2+ year old house, then those blocks are performing. Around here, our AHJs would accept that.