Floor I joists

Picture from a pre-drywall (basement ceiling) inspection but could be found also on a completed house.


The only answer I would have is, "what does the manufacturers specification note with regards to hole sizes and spaces?

One would certainly think by looking at the engineered joists an issue exists.

But like Tyrone said, when an engineered joist is used, one would need to see the manufacturers guidelines regarding…

Drilling with a Chain Saw…:shock:…or very large Hole Saw…:shock:

In general, my answer would be 2, 3, and 4. No I-joist manufacture allows that size or number of holes, period. However, I have worked with several I-joist manufactures to design floor joist for this exact situation.

As a home inspector or third party engineer this situation should be a read flag. Supporting documentation should be requested. Not doing so would be a liability in my opinion.

Since an HI is not certifying capacity or compliance, APA Guide #Z725 can be used as a general reference for I-Joists.

Actually that may be close to being acceptable (workmanship aside), as I-Joists generally can have multiple holes almost the entire web depth as long as they are not near an end and spaced with at least 2 x Hole Diameter of clearance (see page 16-18 of the APA guide available at www.apawood.org).

JMO & 2-nickels … :wink:

The holes look larger than allowed, and the holes do not look round indicating improper enlargement or knock-outs have been enlarged.


Downloadable pdf framers guide.

Second joist from top of picture give you a clue (Right side)… These “holes” were field modified. Notice that the “hole” is not a perfect circle knock out.
At first I was thinking that the sizes maybe fooling since this “insulation” (looks like insulated ducting) maybe fooling but the spacing and number of holes, is just to much per the APA guide that Raymond’s link posted.
Great info Raymond!

Floor a little “bouncy”…hmmmm:o

This would be a good topic at regional meeting groups. I don’t see many engineered floor joists, but some can be very confusing particularly when and where blocking is required, et ceteras.

If there are too many large holes ( I voted for too many large holes) the whole joist is not safe. Hmmmm.

Truss Joists systems are not covered in the building code part 9, but rather is covered under manufacturers guidelines. Some truss joists come with webbinghttp://www3.telus.net/selkirk99/selkirk/Beams/Joists/joist.jpghttp://www3.telus.net/selkirk99/selkirk/Beams/Joists/opjoist.jpg

There are too many variables in this situation. I work with a floor joist company that markets their product for these exact situations. They provide calculations, details, exact dimensions for hole sizes and locations, as well as shop drawings. Stating the floor system is “not safe” when this may not be the case undermines the client/homeowner’s confidence in builder and the home. Additional information is needed from the builder and/or engineer.

As for the floor joist with webbing, you typically can get a larger duct in the joist with a web.

Too many variables = further investigation by structural engineer. By the photographic evidence it appears there is very little webbing left to maintain integrity. It would be interesting to find out if in fact these joists are up to snuff.

There is a company here in VA that manufactures the cure for those I-joists.

Check this out:


Thanks that is a great site, an innovative product! It appears that it can also be used on regular joists as well. This gives credibilty to my theory that notched or cut joists can be sistered without sistering running the full length of damaged/cut joists.


I had an inspection that we questioned the I-beam joists. Checked with manufacture, e-mailed a few pics. They had a rep come by and look. It all checked out, but if you went by manufactures specs it was questionable.

Give a call, see what the manufactures says.

There is noththing wrong with this picture if all the parameters of the Manufactures guidlines were followed.

Off the cuff, I would say that if these joist are at least 11" - 7/8 , are most probably alright, considering the distance between the holes. I would recommend that the Manufactureres guidelines be the determining factor on the evaluation of this concern.

Would recommend a reputable Building Contractor to evaluate the concern as noted.

A Structural Engineer at this point would not be prudent, due to the Engineered Product at hand. Reference to the Manufacturer will be his answer at about $500 dollars.

Hope this helps.

:slight_smile: :slight_smile: :slight_smile:


It is obvious from the pictures that “two times the max diameter” between the holes is not present therefore it is a bad installation.

If the correct spacing was present and it had only two holes it may still be bad due to the required distance from a hole to the load bearing end.
The specs always show two holes max and never three, not sure if three are allowed when the other distances are correct or not, one phone call to a manuf. did not answer all of my questions but I did not have the series number available either.

I did not measure etc. since I did not have the type and series numbers for these to look up the specs. It is obvious that the flanges are not LVL material which means these are the cheaper less strong I -joists available.

I recommended further eval and that the client obtain the builders response in writing. The floor was more bouncy than typical using a 240 pound test force.

Which manuf. uses punch out holes this big? These were cut with jigsaw or sawzall probably.

What is your secret that you can tell the distance between the penatrations?
Am I missing something here, or is this why I am recommending Manufacturers Giudelines?

I do know about the diameter size distance.


Regardless of how many notches, they can’t be less than 2’’ (I believe it’s 2) from top or bottom of joist.

Erol Kartal

All I-joist manufactures provide pre-printed guidelines for drilling the web members that are conservative. My first step is to review the published information for the specific manufacture. If that doesn’t work I then call the manufacture with all the specific information.

You can remove the entire web from a truss and it can still work. The concern is when you do this close to an area with higher shear values (the ends of the joist). I know some manufactures give the 2” to make sure they don’t accidentally hit the top or bottom chords.

I have found that I-joist manufactured with solid wood top and bottom chords are better. They don’t have as many issues with delaminating. There are also more restrictions with the engineered bottom and top chords. You can’t nail into the sides of the engineered chords.

You do not need to cut a round hole in the web. However, it is found that using a hole saw will create fewer mistakes such as over cutting or hitting the chords.

The other item to consider in this situation is the floor joist size/specification. If the engineer (of record or the floor joist only) performed calculations on the three holes, they could have increased the floor joist to address any potential concerns.

This is how I would write this up as a third party engineer:

“The engineered floor joist over the XXX have been drilled to install duct work. Each joist has three holes. The number, size, and location of the holes do not meet the manufacture’s published guidelines for drilling of the I-joist web. The builder should be contacted to obtain documentation for the modified floor joist. If such documentation is not available, the floor joist should be evaluated by a licensed engineer.”