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Discussion Starter · #1 ·
I am running three new circuits for my new shop. There are existing holes but they are pretty full, so I will need new ones. How far away do the new ones have to be from the existing ones. I haven't actually measured them, but they are about 1.5".

The joists are plywood on the top and bottom, with a flake board web. (well maybe not flakeboard, but you know what I mean...)
 

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1.5 inches is fine. Some engineered joist companies print the drilling info right on the product some you have to get a spec sheet. A couple of 3/4" - 1" holes should be no problem.


BTW , it's called oriented strand board (osb)
 

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Discussion Starter · #4 ·
No we do not know what you mean, got a picture?
Are these engineered joist?
http://maner.com/Engineered Lumber/I-Joist Hole Chart.pdf
Okay, I did a search for my TJI 230 and found a similar chart. 1.5" holes are allowed anywhere as long as they are 6" from the supports. Midpoint between the joists two 1.5" holes can be right next to each other. So that pretty much answers my question; thanks.

A related question... it obviously is okay to nail into the flanges to put in pipe hangers and the like. I am going to put up two 50 pound air filters. Since they are supported in 4 places, it wouldn't be more than 20 pounds from any support. Is a screw eye into the flange okay? Is screwing into the bottom or side better? The alternative would be to put a chain though a hole in the web, and that doesn't seem right.
 
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