Floor joist...

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1793

1793

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Louisville, Kentucky
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I was at a job the other day at a new home and I went into the basement of this two story house. I was surprised at what I saw. I was under the impression that size and number of holes would weaken the strength of the beam.
 

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1793 said:
I was at a job the other day at a new home and I went into the basement of this two story house. I was surprised at what I saw. I was under the impression that size and number of holes would weaken the strength of the beam.
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It may be fine



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If this is something that was done at the factory then the size and placement of the holes was engineered into the joist. The engineer's stamp of approval is all that is needed.
 
By the shape of those holes, it appears that they were not cut onsite, meaning I would think they were engerniered for the application.
 
I have seen thes before in that type of joist, but not as large. They are just like a knockout in a j-box, you just take a hammer and rap it a couple of times and it pops out.
 
1793 said:
I was at a job the other day at a new home and I went into the basement of this two story house. I was surprised at what I saw. I was under the impression that size and number of holes would weaken the strength of the beam.
Click to expand...

I've seen plumbers cut 4" holes in these truss joists. You just have to keep them a certain distance apart.
 
Visit the trade group for the rules. It's the "engineered wood association," or www.apawood.org .

The short version: there's no way those holes are allowed.

Field made? I think so. Factory KO's never line up that well. Someone just did a very neat job.

You're right ... the size and placement of the holes does matter- and the 'rules' are quite different than they are for ordinary lumber. They're different, yet again, for gluelams.
 
If these are not factory placed holes, then the joist manufacturer provides a chart which should be supplied with the joists. The chart will list the conditions under which holes can be bored in the joists. These holes seem a little large, but may be ok. The size of hole allowed will depend on the design specifications of the joists and the distance of the hole from bearing points. The farther the hole is from the bearing points, the larger the hole can be.

The chart will be conservative in its allowances. If the holes are not allowed by the chart, there should be a phone number on the manufacturer's information booklet which can be used to contact the manufacturer's engineers. They will look at specific jobs and determine whether the holes are allowed in a specific case.
 
renosteinke said:
Visit the trade group for the rules. It's the "engineered wood association," or www.apawood.org .

The short version: there's no way those holes are allowed.

Field made? I think so. Factory KO's never line up that well. Someone just did a very neat job.

You're right ... the size and placement of the holes does matter- and the 'rules' are quite different than they are for ordinary lumber. They're different, yet again, for gluelams.
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You might lose that bet. See here for some info on Trus Joist. The TJI 110 product is available with an overall depth of 9-1/2" with a web of 7" and allows a 6-1/2" rectangular hole at 4'6" from an end support, so you have just 1/4" of web left top and bottom. I can't tell from the photo for sure, but it looks like there's enough web left. I'd say the holes could definitely have been field cut.
 
gadfly56 said:
You might lose that bet. See here for some info on Trus Joist. The TJI 110 product is available with an overall depth of 9-1/2" with a web of 7" and allows a 6-1/2" rectangular hole at 4'6" from an end support, so you have just 1/4" of web left top and bottom. I can't tell from the photo for sure, but it looks like there's enough web left. I'd say the holes could definitely have been field cut.
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Great link. Thanks for posting.
 
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