ECN Forum Forums General Topics of the Trade General Discussion Area prefab floor joists? how too?

Mornin! I need to price a job that has been stick built yet the are using the prefab floor joists. the ones with a piece of plywood on edge and two sticks glued to each edge. just trying to figure out my hours for this job. how to wire it. i'm pretty sure you cand put holes in them. any help would be great

There have been many discussions on this, here is one https://www.electrical-contractor.net/ubb/Forum18/HTML/000053.html

A friend of mine broad back a scrap of one form a construction site. There were these knockoutse scroed in them you just knock out with your hammer.

I don't even conceder if it has enginered joists or standard 2X when bidding. So many varebles in a job I don't think it makes too much difference.

Myself I think it's a plus when they have I-joists cause they drill fast. They don't seem to use cross braces with them here too which is on less thing that might be in your way.

Tom

Tom

At this time last year, I was wiring my first building with these things.....

I was very fortunate in that I had an absolutely free hand in deciding what receptacles went where, light placement, etc. I also, unfortunately had absolutely no information as to room layout, equipment location, etc.

This was particularily vexing, as with this type of construction- and unlike regular feaming- there is absolutely NO going back and making changes or additions later on; you pretty much only have one chance to 'get it right.' Once the drywall is up, any changes call for major, and I mean major, work.

I was lucky; my guesses were 98% on the money. The remaining two were- luck again- possible with minor work. (I was able to remove the cove base, rout a slot for the wires, and re-cover. The MC used was also protected by a length of steel channel).

Yes, some have pre-punched holes for utilities. I have found them to be tough to knock out. They do drill fast and where you drill is not as much of an issue as dimensional lumber.

One thing to watch for is the spacing. I have had to drill some that were on 12" centers. Make sure you have a right angle drill and a very short spur bit.

Silly carpenters almost NEVER put those holes anywhere close to lining up. Rare if they even think of it. Most can be drilled*, per manufacturers +/or engineers instructions. Always check with GC, and engineer if they can or can not be drilled, and for what size holes.

*Add a set of bits into the bid for the job, the glue in them trash bits like no one biz... 2 sets for a large job.

Here's a horror story about these. On a job 6-7 years ago, (When these were kinda new) the GC had a meeting about them, and said under no curcumstances should the ones on that job be drilled in any way. Everything in the cieling had to enter from the sides. (We ran a gutter down both sides and that was it for us, a pipe down each wall and a whip for each set of lights between the joists.) The building was open spanned from property line to property line, short dimention was 50', with several tons of AC equipment on the roof. The cieling had several sections with these engineered beams, and glue lams stacked next to eachother.

While I'm up in the lift at the gutters, I notice the Sprinkler guy drilling the mess right in the middle, so I yell over to him that he wasn't supposed to drill them, and we argue from two different lifts. "Just following the plans..." None of my biz, etc. The GC is no where to be found all morning. My boss shows up, and I tell him. So my boss calls him, and the GC is back in a flash. He then throws everyone off the job site, and he's hopping mad, throwing stuff. We don't go back for 3 weeks or so. When we do go back, there is a giant steel beam down the center of the building. And a new sprinkler sub... Apparently these all started to split at the 4+" holes that were drilled, but that probhably had more to do with the glue lams.

Get manufacturer specs before drilling any holes in them. Get the GC to sign off on anmy holes in the micro lam beams as well.

NJI -

Go to:
http://www.aecinfo.com/1/resourcefile/00/22/89/bcwspe22.htm
This will give information about hole location and sizing.

You can also call Boise Engineered Wood Products at 800-232-0788. They are very helpfull.

Steve

They take longer to staple wires to if you are running the length of the thing. Lots of bounce back.