Squash Blocks

Hi. Will;

Hope you are doing fine.

Take a look at this and it should explain Squash blocks.
[In addition to point loads, squash blocks are required below bearing walls. If there is a load bearing wall above the beam, then your suspicion is correct.

I spend most of my career crawling under farmhouses, but occasionally recent additions are constructed with engineered building products. I have pointed out omissions of squash blocks, filler blocks, etc., on numerous occasions and the contractors always claim - “It’s AHJ inspected and approved.” Turns out in my rural area the AHJs do not evaluate these floor systems since they should be installed as per manufacturer’s specs.

Go to APA performance Rated I-Joist frame 1D.
Hope this helps.

Marcel:) :slight_smile: ](http://www.apawood.org/level_b.cfm?c<P> </P><P><FONT face=)</IMG></IMG>

Thanks George.

I thought we were talking about the flooring because that is what is shown in the pictures. Walls are always sheeted with the 1/2 OSB, occasionally black fiberboard is used in non sheer locations.

There were big homes in california where they started using 1 1/8" plywood for floors in all the bathrooms. Man, it was heavy! Can’t remember how they made the flush transition back to 3/4" at the doors.

Did I miss something?

I read above that 1/16" gap is necessary for the squash block(s.) Those in the pictures seem to be gapped at 1/4 - 1/2"? I would think if this is true that these are going to be a problem down the line if the underside of the I-joists are not shimmed - right?

**Squash Blocks
**Sawn pieces of lumber to be nailed to each side of an I-Joist at the location of a post, load bearing wall, or concentrated load up to 4000 pounds. The squash blocks are cut 1/16" longer than the depth of the I-Joist to insure proper load transfer.

Here is a pretty good APA guide on Squash Blocks …

Re: Squash Blocks
**Squash Blocks
**Sawn pieces of lumber to be nailed to each side of an I-Joist at the location of a post, load bearing wall, or concentrated load up to 4000 pounds. The squash blocks are cut 1/16" longer than the depth of the I-Joist to insure proper load transfer.

Thanks guys,

My point is that the blocks shown appear much longer that they should be and will distort the load transfer - won’t they?

Dennis, it looks to me like the bottoms of the blocks are resting on the beam and there might be a small gap between the blocks and the sheathing.

It looks like there’s a gap of close to 3/8" between the joist and the beam, so the blocks will pick up the load before the I-joists touch the beam.

If the load increases for some reason (snow, impact, etc.) it will be transferred to the beam through the squash blocks. I don’t think anythng will distort… the load path wil be through the sheathing, to the blocks, to the beam and then on down to the foundation.

The purpose of the squash blocks is to pass the load around the I-joists.

Since the gap between the joists and the beam is bigger than the gap between* the* blocks and the beam, when a load is applied, the blocks will pick it up before the joists.

When the gap above the blocks has closed and the blocks are fully loaded, there will still be a gap between the joists and beam.

The blocks will transfer the load to the beam and from there it will be routed to the foundation.


I do not disagree. However, if shims are not under the bottom of the I-joist the full load is transfered through the surface area of the 2x4" block ends. The top of the block, being met by the particle board sheeting could push its way through the sheeting because the load in this area is not shared by neither the top nor the bottom of the engineered I-joist. I realize at this point (and not before) that the blocks are there because a bearing wall is just above, so the top of the sheeting is pressed into the bottom plate of the bearing wall by the block. And, the bottom of the blocks now distribute the weight from the bearing wall above to the outermost edges of the support beam/post/etc. When shims are used the weight is evenly distributed across the top of the sheeting and the top of the beam/post/etc as the engineer intended. Further, the manufacturer of the I-joist compile their span specification with the intent that the bottom of the I-joist will be stressed in compression at this point - without the shim the bottom is stressed in tension, a very different scenario than the manufacturer intended. I would fear unanticipated lift of the ceiling joist at the top of the bearing wall and perhaps distortion of roof line. Right?
This, I believe, is why a maximum of 1/16" is specified when the block is cut.

Kenton you are correct
If there is something wrong here it is that the beam was installed lower than the exterior walls. Because these joists do not come with crowns in them they are strait. If the beam was installed at the correct height everything would look the way it is supposed to.


Thanks for the informative link. Curiously, it specifically states, 1) that the squash blocks are not intended to replace blocking along the length of the load bearing wall, rather intermittently to allow passage of duct work; and 2) the 1/16" extens above the top of the I-joist cord (NOT the bottom.) From this article and the pitcures at the beginning of this post, I would note that two inappropriate conditions exist.

I think the intent of (1) is that squash blocks are not a general replacement for solid fire blocking (required at all bearing walls with ceilings). The intent of (2) is that the block be 1/16" oversized and “jamb fit” to ensure that bearing is on the blocks and not the I-Joist web.

Note that for certain I-Joists and light loads, some manufacturers don’t specify squash blocks. Even in those cases I still think it is considered good practice to have squash blocks at any bearing wall locations whenever there isn’t solid blocking.

JMO & 2-nickels

The only thing left that is yet a thorn in my side is the extreme gap at the bottom of the I-Joist. I just cannot believe that it is okay to be contrary to recommended practice. If any of you live close to a Trust Joist EWP plant (or another mfg.) it would sure be nice to get their final word. On the other hand, I can e-mail the question. :slight_smile:


Yep. That wall should have solid blocking to uniformly tranfer the load to the beam. The squash blocks create a series of point loads. It’s a squirrely situation because if the downstairs wall is supposed to pick up the load from a bearing wall above, you’d expect to see joists resing on that wall.

Well said. :slight_smile:

Actually, the purpose of the squash blocks is to transfer load from a bearing wall above to the girder. The bearing wall bottom plate and sheathing transfers stud loads to the squash blocks. That usually works fine as long as jack studs for large openings or posts are directly supported by joists (or blocking where it falls between two joists).

It looks like an unfinished basement, so solid fireblocking wouldn’t be required. But blocking or some other means to prevent rotation of the joists is required at ends. However that blocking is usually not “jam fit”, so the load is primarily transfered through the squash blocks even when there is solid blocking.

That is strange that the I-Joists are up above the beam plate, and I am left wondering if there are shims under them. Perhaps there was a slightly deeper member bearing on that girder, so the floor level is higher than the joists in that area?