Furring down from trusses
I just received the engineering for my truss system and see that where I want to fur the 5 in 12 scissor trusses down with a 2×6 (so that I can insulate the attic out to the ext. walls), the notes say, “This truss design requires that a minimum of ½” gypsum sheetrock be applied directly to the bottom chord.”
Trusses NOT over the vaulted great room spec “rigid ceiling directly applied or 6-0-0 oc bracing.” Bracing is allowed in lieu of rigid ceiling elsewhere in the house.
I still want to add additional insulation like I had posted on GBA.com earlier, https://www.greenbuildingadvisor.com/community/forum/energy-efficiency-and-durability/101764/insulating-512-scissor-truss-system, but now I need to meet the requirements of the truss engineering too.
Furring down from the scissor truss removes the sheetrock from being “directly applied” to the trusses AND creates a hinge between the sheetrock (diaphragm) and the truss.
Before I talk to the engineer, is there some way that a combination of blocking and/or bracing would satisfy the structural role of the sheetrock? The obvious need is to prevent the bottom chords of the vaulted area from deflecting laterally when the roof is under a load, snow, wind, or seismic.
I WILL NOT take any replies to this post as being legal or engineering advice. This is just ideas for a solution.
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Replies
Have the truss company add the dropped 2x6 into the design. They can press on the drop section with side plates. This then makes it part of the truss and solves you issue.
It would help to have a drawing of the truss, but I would think that you could install drywall to all bottom cords and then frame your fur-downs. We do it all the time when creating duct chases inside the conditioned space.
Sorry, I should have looked at your link first. You need at least 15"-16" heeled trusses to properly insulate with R49 plus you need 2" for the ventilating baffles. Your insulator can blow-in insulation before you install drywall by using a net under the bottom cords, cutting 22"x24" blowing holes and sealing net. Insulation will not slide on a 2 1/2/12 pitched truss. It is done every single day in the SW with low-scissors and flat roof trusses.
Tim, Armando, Thanks. This whole thing is a work around because the builder priced raised heels like he didn't want to do them.
These ideas help.
You can do a standard truss then have the truss yard press on the drop you want on the ceiling. This could keep the construction standard except for the drop at the ceiling level. Instead of the raise at the heel, that is causing you contractor to deviate from his standard construction.
Option 2
Yes, you can have the truss design made to have other than the drywall ceiling as bracing. The truss yard can make that change. They would change it in the truss design software to callout alternative bracing. You need to talk to the truss mfg. They have limited choices in the truss program for the bracing configuration. Ask them how it can be changed and what options they can select in the design program.
"because the builder priced raised heels like he didn't want to do them." REALLY? I question your builder knowledge and integrity! Pay now or pay later. Not having heeled trusses can create a whole other issues for you later on, and more than likely, you'll pay more for the fixes. Also, your trusses are not meeting code. I can tell you for sure, your builder not only doesn't own a code book, but probably never read one either.
I only see as an option to condition the attic with CC rigid foam above the roof decking and OC foam under the roof decking, making it much more expensive than the heeled trusses. Horrible advise from your builder.