Pattern-cut HVAC holes in I-joist webs
Watching one of the TOH shows a while back, in which they had Tedd Benson’s outfit doing a whole lot of preengineering and shop fabrication of components, one of the things that struck me was having all the I-joists getting their webs bored at a CNC cutter, for plumbing routes.
So I am doing the plans right now for a guy who will do forced-air HVAC, and run the ducts through the floors, and I’m thinking, why can’t he do sort of the same?
It’s not as if he can lay this off on his HVAC sub, all the cuts through the joists. This guy will self-build this whole house, and it is he that will benefit if this job can be made any easier.
If anybody reading this is thinking, “OMG, some dumb homeowner who thinks he can build this himself . . . , ” then throw those thoughts away. This guy is as capable of doing a ground-up total package as anybody who frequents this forum, and I’ll bet he can beat just about anybody’s schedule, also. Since he does everything himself with his own hired hands, there are zero waits for subs, and everything happens in quick sequence.
Back to topic. Round ducting will be used, and the pic attached shows what we are talking about for holes. It seems to me that if you have a pattern for your router, and you know where the hole is to go before you set the joist on its supports, it would be far easier to rout the hole before the floor frame gets built.
Have you done this? How did it go?
Replies
I built my floor system with TJIs. The documentation that comes with the beams, and the more in depth stuff you can get from the company is quite specific about the size and location of holes. Large ones, like you show, can be placed at the extremes of the joist with impunity. However, when they are as close to the ends as you show they should be reinforced with, for want of a better term, web reinforcements. Just pieces of the web material, or plywood (what I used) on both sides of the web, and in my opinion, on both sides of the holes. I glued mine on with PVA.
Stef
Edited 4/20/2009 10:29 am ET by fatboy2
If the guy is truly capable ... then he already has gone to http://www.apawood.org and downloaded this free publication:
http://www.apawood.org/pdfs/managed/D710.pdf?CFID=1703048&CFTOKEN=11415433
The publication addresses all design details, including the size and placement of the holes. I think you'll find the holes you pictured break a few of the rules.
I should have anticipated the remarks I would get in response to hole sizing and placement relative to joist bearings.
You are preaching to the choir on this subject. We are more than well aware of all the engineering considerations when whacking holes in webs, and have all pertinent publications.
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"A stripe is just as real as a dadgummed flower."
Gene Davis 1920-1985
Gene,
From what little I have seen on this product, I was under the impression that you spec'd the locations from the factory.
dunno
"When the spirits are low, when the day appears dark, when work becomes monotonous, when hope hardly seems worth having, just mount a bicycle and go out for a spin down the road, without thought on anything but the ride you are taking." — Sherlock Holmes, 1896
(Structural issues aside) the biggest challenge I've run up against in similar circumstances is that if the joists aren't all nicely aligned at the rim (vertically and horizontally), your perfectly placed holes don't line up.
1. Make sure all the I-joist ends are squared off before measuring out hole placement.
2. Try to remember which end goes where. (You laugh, but...)
3. Check rim joist and sole plate for deviance, either bow or creep. It's not hard to get out by enough to cause problems running rigid utilities.
Otherwise, lord, yes! It's a lot easier to make those cuts with a template & jig saw on a couple of sawhorses than a sawzall in a crawlspace.
Chances are you'll still have to make some modifications, but if you can resist major changes then it seems like a no-brainer.
k
Edited 4/20/2009 11:39 am ET by KFC
"Nothing is impossible for the man that doesn't have to do it himself."
The pre-routed holes would probably work well with flex duct, but with steel duct, there would likely be carving of the sides to accommodate small changes that seem always to occur in the field.
so he's going to install the hvac pipe at the same time he installs the floor joists or he'll have to cut it up into a million little pieces, pipes running through the joists usually interfere with some other run, hot vs return, plumbing etc .. i think this might be allot like pot lights, no matter how carefull you plan the joist locations, they wind up in the way anyways ..
so he's going to install the hvac pipe at the same time he installs the floor joists or he'll have to cut it up into a million little pieces, pipes running through the joists usually interfere with some other run, hot vs return, plumbing etc ..
That's a good point - on the TOH episode, a lot of the floor and wall sections were prefabbed offsite with the plumbing, HVAC and electrical already installed, so they got around that problem.
I like the pattern and router idea.
However, I think it may be easier to cut the holes in place vs. on the ground.
1) Misalignment is possible during installation which would negate any significant time savings.
2) I think it would be less work to move your ladder/work bench around and deal with cutting over your head vs. moving the I joists around and having to measure and cut each one individually. If these are 40' 16" monsters, just moving a joist to a different spot on the horses can take quite a bit of effort.
Just my opinion.
Jon Blakemore
RappahannockINC.com Fredericksburg, VA
If your guy wants the mechanicals run within the floor joists, then look at 18" deep trusses. Have the plumbers and sparkies run their stuff right at the bottom of the top chord. Then the only problems come from plumbing waste lines. A little planning there will go a long way.
If truss sway braces need to stay, then increase the height, or install them differently.
In order for the I joist idea to work, everything will need to be coordinated beforehand between the carpenters, plumbers, HVAC and electricians. Plans will need to be modeled in 3d and checked for collisions and hole placement.
I'm not saying it won't work, but the amount of planning required would be intensive, and all involved would need to stay within the lines.
It is relatively easy to order trusses with a larger rectangular opening or two that will accomodate larger rectangular duct. That opening needs to be accessible from the exterior to avoid installing duct in 20" pieces. And yes, someone may still put the truss in backwards.
$.02
Edited 4/20/2009 1:47 pm ET by danski0224
I think it would be easier with parrallel chord trusses from a truss company. Boss and I talked about this a long time ago here. Get the HVAC guy in touch with the truss company and it may be that no extra work is required when the trusses are built with HVAC in mind.
Cutting things on a cnc may not be any quicker unless he finds someone to do the software file for him. Learning a 2-d or 3d software package has its own learning curve and then there is the cam software and the cnc interface software. It's probably a lot less hassle to just cut the stuff out on site.
I think it is a great idea.
I always tried to get the plumbers, HVAC installers and electricians together on site, at the same time, to layout joist bays, heat registers, drain pipes, can lights, and so forth, before the plumbers began their butchering.
In theory it would be possible to do all this from a set of plans if they are detailed enough. All critical joist and stud bays need to align and the framer will not be allowed to deviate from the plan. A doubled stud in the wrong bay may not allow room for a duct and say a vent pipe. Plumbers may want to know rafter locations to locate which stud bay they could run vents up. The joist layout would have to be exact (allowing for plumbing drain locations, stair headers...) with no deviations.
It's all possible, and it would be cool for the trades to come in and have all their holes cut for them--can you say price reduction? And if this were a volume home builder, building the same model over and over, the time/cost savings could be tremendous.
But, the amount of time spent in planning, extra care taken in framing and the risk of the unforseen, change orders, or even making a mistake, for a single home would negate the benefit. If it were me, I would utilize the great router/template idea to cut holes after the framing is complete and the trades have marked out their territory.
Edited 4/20/2009 3:10 pm ET by levelone
I figure he should install the beams, then just set up an NC laser at one end and cut them all in place. All the holes would be guaranteed to line up. (Keep a fire extinguisher handy!)
If I am not mistaken tji ijoist has the service avalibale to pre cut you holes for heat runs. And electrical. its next phase job pack.
Edited 4/20/2009 6:58 pm ET by mgard38
Gene
It is still early enough in the game to look @ a different product that has proven to me to be very cost effective in the past. Take a peek @ the Deitrich Trade Ready Floor System, it comes pre punched to allow for any type of HVAC layout and its fast. The first time you may lose a little efficiency in the learning curve of how it all comes together but you make it all back up later, especially if this gentleman is running all phases himself. I have used it many times for structural light guage metal framed homes and condos,its easy to hybrid too, LGMF floor system, and wood framed Exterior and Interior Partitions. The FP is sent in, engineering is done joists are rolled, rim is built with layout in place, hits the site and put it together. I have seen productivity savings across the trades of 30 - 40%, we swear by the stuff. It took me a while to sell it to the guys, but now they want nothing else. Just my 2 cnts.
Trace