Thread: Squash Blocks & I-Joists

Are squash blocks needed where I-Joists support the bottom of stairs?

Your opinion??


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Yes, because those are not intended to carry the load like that at the end, they need resistance to that squashing effect, thus the squash blocks.

I agree, and you can never have too many squash blocks with engineered joist!

Rim board would have been a lot easier. I doubt it would ever be an issue, unless Aunt Bertha weighs 1,000 pounds and is dancing on the stairs.

Not required. Read Manufacturer specs. and requirements for understanding of squash block usage. I see no need to recommend them in this instance. There is no substantial load transfer here.

Eric,

I agree, four of those are plenty even when the load is across the ends.

If the stairs are not properly installed and supported at other areas then that is a different issue.

Originally Posted by Eric Barker

Not required.

Read Manufacturer specs. and requirements for understanding of squash block usage.

There is no substantial load transfer here.

.
How much weight ( how many stairs ) coupled with the probable ( over the life of the stairway ) one time Live load could the Stairway be Expected to Carry?
* I'd go for the blocks.

Originally Posted by Eric Barker

Not required. Read Manufacturer specs. and requirements for understanding of squash block usage. I see no need to recommend them in this instance. There is no substantial load transfer here.

Eric,

Would you guide me to that and point it out?

This ( http://www.ilevel.com/literature/TJ-9001.pdf ) shows squash blocks as being specified at (go to page 3) detail B2 and states "Use B1 or B2 at intermediate bearings with load bearing or shear wall from above". Now go to page 2 and see B1 and B2.

B1 is web stiffeners and B2 is squash blocks.

Looks to me like the correct way would actually have been Rim Board or Rim Joist. Which is even stronger than squash blocks.

Looking for some education, where does it indicate that nothing would be required?

Properly installed staircases have intermediate support (studs or braces) and stringer fastening to the adjacent framing.

The max load on that bottom area resting on the four I-joists would be nothing of concern.

Even if that application falls under the same category as a load bearing wall it should not be and is nothing to worry about.

Its one of those calls that can be made if your unsure but I would not write that up as a problem.

Specs call for the squash blocks when there's a load bearing wall above such as transfer from second floor. In a ranch, for example, the blocks are not required at the load bearing points - the I-joists are only carrying the weight of the floor which should be able to carry 40 lbs sq/ft.

So for a stair landing there's no such weight or load transfer. Looking at Erby's photo I don't think that there's an issue and to say otherwise would be an uphill battle.

Did everyone notice that those I-joists have LVL chords instead of regular lumber?

Originally Posted by Bruce King

Did everyone notice that those I-joists have LVL chords instead of regular lumber?

Weyerhauser says their I-joists have recently been "Upgraded" to increase span, load, and overall construction costs. -We are one of the communities that have experienced tragedy from one of the earlier (possibly incorrect) installations of I-joist floor systems, and so naturally skeptical. (pile of dead firemen in the basement tangled in remains of I-joist floor system) We have only just begun seeing these again in residential construction.
-I have struggled to keep up with the mfr.s info especially blocking requirements, the last 5 or 6 years, it is very compressed, dense data, and it does get revised from time to time. You need to read and re-read and look closely for your specifc application.
-My office has engineered blocking for quite a few applications that I-Level didn't mention. With this latest upgrade I see the literature now includes quite a bit of blocking. (is that a good thing or a bad thing?)

-I agree, there doesn't appear to be any undue load at the bottom of the stairs, if they have been properly installed otherwise.

-And I also agree, with wooden i-joists you can never have too much blocking.

Originally Posted by archivoyeur

Weyerhauser says their I-joists have recently been "Upgraded" to increase span, load, and overall construction costs. -We are one of the communities that have experienced tragedy from one of the earlier (possibly incorrect) installations of I-joist floor systems, and so naturally skeptical. (pile of dead firemen in the basement tangled in remains of I-joist floor system) We have only just begun seeing these again in residential construction.
-I have struggled to keep up with the mfr.s info especially blocking requirements, the last 5 or 6 years, it is very compressed, dense data, and it does get revised from time to time. You need to read and re-read and look closely for your specifc application.
-My office has engineered blocking for quite a few applications that I-Level didn't mention. With this latest upgrade I see the literature now includes quite a bit of blocking. (is that a good thing or a bad thing?)

-I agree, there doesn't appear to be any undue load at the bottom of the stairs, if they have been properly installed otherwise.

-And I also agree, with wooden i-joists you can never have too much blocking.

Sad about the firemen but that could have been any type of frame. Fire burning, twisting and melting everything everywhere.

Anyway I would have treated the understair situation the same as I would have treated and joist termination of any floor with a rim joist.

All these questions and ifs and maybe's. How much could it have possibly taken to end the joist run properly. Not to mention the underside of the floor being wide open.

Squash blocks are not required, but lateral support for the ends of the joists are. See details A1, A2, & A3 in the provided instructions, they need a rim joist made from LSL or another TJI, or a blocking panel

Originally Posted by Fred Weck

Squash blocks are not required, but lateral support for the ends of the joists are. See details A1, A2, & A3 in the provided instructions, they need a rim joist made from LSL or another TJI, or a blocking panel

Would not simple squash blocks serve the same purpose? The idea is to keep the top/bottom cords from crushing under the weight that they are supporting. They are most vulnerable at their ends.

Heck, could not hurt anything anyway to recommend them. Truth be known, that staircase will not really be producing that much of a load.

Originally Posted by Scott Patterson

Would not simple squash blocks serve the same purpose? The idea is to keep the top/bottom cords from crushing under the weight that they are supporting. They are most vulnerable at their ends.

Scott,

That was my first thinking to, but after reviewing the installation instructions the use of the rim joist/header is shown as being required where there is a load transferred from above, and it does not specify a load bearing wall, as one post suggested above.

Also, a "properly installed stairway" does not require intermediate support, it can bear at the top and the bottom of the stringers.

Additionally, if there is any shifting under load, only the rim joist/header would keep those upright, squash blocks would not provide that same lateral support.

Unlike some other posts above, I would not be designing and accepting something which the manufacturer themselves does not accept. Not sure why others would or do, but that is them and not me.

As a Carpenter, I would put something in there to help distribute the dynamic vector forces which occur during day-to-day use of the (load bearing) stairs and landing. If an objective is to be able to shoo away critters, then use squash blocks and diagonal bracing; if critters are not an issue, then the installation of blocking or a rim joist put to rest any uncertainty of shifting or unexpected failure of this structural system.

As an Inspector, I would encourage the buyer to have a local code enforcement official sign off on this.

Originally Posted by Thomas Kirchner

have a local code enforcement official sign off on this.

They probably already did!

Originally Posted by Thomas Kirchner

As a Carpenter, I would put something in there to help distribute the dynamic vector forces which occur during day-to-day use of the (load bearing) stairs and landing. If an objective is to be able to shoo away critters, then use squash blocks and diagonal bracing; if critters are not an issue, then the installation of blocking or a rim joist put to rest any uncertainty of shifting or unexpected failure of this structural system.

As an Inspector, I would encourage the buyer to have a local code enforcement official sign off on this.

Hmmm

A carpenter huh. I must be getting old. When I was playing carpenter years ago in Mass and started talking "dynamic vector forces" I would not have lived that down for years.

Just ribbin yuh. No offence

Originally Posted by Ted Menelly

Hmmm

A carpenter huh. I must be getting old. When I was playing carpenter years ago in Mas ans started talking "dynamic vector forces" I would not have lived that down for years.

Just ribbin yuh. No offence

Ted,

I wrote him off as being a "carpenter" as no "carpenter" talks like that.

At least not any of them I've seen in the last 20 years or so ... (of course, even calling them "carpenters" is using that term very loosely and with literary license)

Welcome to THE inspectors board, Thomas. We need a good "carpenter" here.

Originally Posted by Ted Menelly

Sad about the firemen but that could have been any type of frame. Fire burning, twisting and melting everything everywhere.

Once fire has entered an unprotected wood framing space the building is toast. Fire codes usually are meant primarily to slow progress of flames to the fuel. I remember reading a fire test that showed the difference in time to collapse of a conventional framed roof to a trussed roof was like 10 minutes vs. 9 minutes. Once the flames are in the attic space the building is unsafe no matter the method of construction.

Originally Posted by Erby Crofutt

Are squash blocks needed where I-Joists support the bottom of stairs?

Your opinion??


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Since you're looking for opinions, if I were a framer, homeowner, architect, or code official, I would want a letter from an engineer stating that they are not required. Not every condition is clearly called out in the manufacture's online PDF files. Maybe you could point out that it might be a problem and recommend they seek a professional opinion.

I guess you never really know who you're gonna meet these days. I read some engineering books a long time ago.

Originally Posted by Thomas Kirchner

I guess you never really know who you're gonna meet these days. I read some engineering books a long time ago.

I slept at University once. All those old vibes just kinda worked their way into the brain cells. Man my head hurt for years after that.