I have a set of prints for a custom home. The house is calling for TJI’s for the first floor. Code requires that the underside is to be rocked with 5/8†and fire taped. The basement will not be finished until a later date. Most unfortunately, the inspector will not allow me to soffit out the ductwork and rock it after all the mechanicals are installed. What do you think is my best approach?
My thought is that furring down the joist with a double 2x should allow most of the mechanicals to be surface mounted on the bottom of the joist. I can then rock over the top of them without making the subs drill everything out – lets assume that I am going to do this.
I will still need to fur down, rock, and tape above the ductwork. My thought is that I will do this before the ductwork is installed because I don‘t believe I will be able to at a later time. Then after the remaining mechanicals are installed fur down, rock, and fire tape the remaining. Is this extreme? I can not think of a better way, but I think there must be one that is not coming to mind. Any experience with this or thoughts?
Rocking over the top of the mechanicals will cause some problems tying in at a later time but I have to be realistic. Without a print for the basement I feel that covering them is the best coarse of action at this time.
Replies
What is the reason for not being able to soffit the mechanical chases? Is there a way to install draft stops assuming this is the issue? Where are you?
John
I'm in the Chicago Area. He wants the drywall in direct contact with the TJI's. Why? I don't know.http://www.multichambernailgun.com/b2/
Did you ask?
Sounds kinda odd. I'd talk to someone else who has built homes and finished the basements in your area to see how they worked around this hurdle. You can't be the only person who has encountered this problem. Did you let him know that you plan to finish the basement? You need this to complete the framing inspection? How are the plumber and electrician supposed to work with the ceiling in the basement already rocked? Is it possible to just rock where your ducts will run, then let everyone else finish their stuff, then come back and complete the the drywall and tape it?
Why not just install a full sheet along the path where the ductwork will run? A lot of times in basements the trunk lines run parallel and close to a beam or bearing wall. I wouldn't think the furring would give the HVAC guys any more meat to fasten to than the I joists already do.
When you say "mechanicals", are you just referring to HVAC or are you including PL and EL in that? If the latter, I would insist that the conduit and supply pipes be in the joists bays and not below the ceiling level. Waste lines should be up there whenever possible.
Does you inspector want the sheetrock for fire code reasons or to brace the bottom chord of the I joists?
Jon Blakemore
RappahannockINC.com Fredericksburg, VA
I appreciate everyone’s input. I am working 6 -12’s this week. I will have to respond to everyone next week. Thank you for your input and thank you for your patients.
The inspector wants the drywall in direct contact with the bottom of the TJI’s. Building a soffit around the ductwork after would leave a cavity open between every joist space allowing fire to run freely. In my original posting I stated that I would fur down, rock, and tape over the ductwork before it was installed and finish the remainder after all the other subs are finished. I’m still looking for a better way. Any thoughts?
I think you bi is trying to get you to elminate a complete open plenum that will feed a fire if it starts. In MI, we had to break the ceiling plenums into 500 sf max in some localities.
You are right on the money. I have to eliminate the plenum. http://www.multichambernailgun.com/b2/
We had to break the plenum up into sections no greater than 500sf. It was much better to do it before all the mechanicals were done. Then, go back and patch where necessary.
the last code ref I saw on this I thought said 1000sqft. Is it smaller now? Was it a code ref that drove you to <500sqft?
The last time I had to break up a plenum, the requirements were 500ft. That might have been a city requirement. There were many cities that never checked.
is there a difference between areas of open web floor joists and a plenum? I'll have to dig it up again. I'm under IBC 2006.
A plenum is created in open web joists. To slow down a fire, the fire department insists on the open web joists to be draftstopped into segments not larger than "x" amount of square foot.
I'll see if i can dig up the ref today. We are talking the same thing.
why do you need to fur anything down? Rock the joists where the ducts will run, let your electrician and plumber do their thing, then finish rocking the joists, tape and finish. Then you can have your HVAC completed. I'd still ask the building inspector how he suggests you go about finishing the basement.
I can’t ask the other trades to drill every pipe in every joist, I have to allow them to surface mount to the bottom of the joists. After they have installed all their pipes [surface mounted to the bottom of the joists] I can add furring to the bottom of the joists and rock almost the entire ceiling without having to tape into any pipes.
As far as finishing the basement you can always install a drop ceiling or surface mount and fur down again. The foundation has 10’ walls.http://www.multichambernailgun.com/b2/
furring across the joist will still create a fire chase . would it not?
The furring goes parallel with the joists not perpendicular.http://www.multichambernailgun.com/b2/
I think you should buy yourself a right angle drill and make all the holes for the Electrician and Plumber yourself. That would probably be cheaper (both materials & labor) than a double layer of furring, and you would get, IMHO, a better job.
Jon Blakemore RappahannockINC.com Fredericksburg, VA
Maybe I just use patient subs, but when ever I tell them that there is the potential to finish the basement, they always run everything they possibly can in between the joists. Main lines run along a center beam, and then up and over from there. I've never felt bad asking them to do it this way. HVAC of course will take up alot more room, but aside from the trunk line, most of it can still be run in between the joists. Am I missing something here?
TJI's are solid web trusses aren't they ?
So they should have knock outs for the smaller pipes and electrical.
I would think it would be possible to have HVAC partial installation done and rock around that and then simply rock the TJI's.
Van of Fire Stop foam works for between joist areas penetrations.
They can't get your Goat if you don't tell them where it is hidden.
I think you need to ask your BI some pointed questions.
In my experience what the BI wants or thinks is a good idea personally and what the actual code requirement is are two different things.
If he can show you chapter and verse where his way is the only right way? Then you just have to deal with it.
I'm betting he can't. Instead he's going to point you to a code which allows for some interpretation. And that in turn will put you in the position to bargain a little with him and maybe meet in the middle.
New Jersey used to (maybe still is) full of BI's who made their own personal "Good Ideas" the code until someone questioned it.
Very good point but his final decision is the rule whether it is right, wrong, or I agree with it.http://www.multichambernailgun.com/b2/
Can you use mineralwool batts to show the inspector that combustible materials are protected and fire stops provided around the duct? Hope this helps.