Remove blocking between LVL joists for HVAC return
Hello,
I am adding a second story using 9.5″ BCI’s and LVL’s as floor joists. The LVL’s are being used on a section that will cantilever about 16″. With BCI’s, I know that blocking is required at cantilevers. Some of the reason for using 1.75″x9.5″ LVL’s instead of BCI’s was for easier blocking (easier as a newbee), not having to use stiffeners at the end where the new wall (load bearing) will sit, etc…. I will still be using LVL blocking at the cantilever. However, I do have 1 bay that is going to be used for my Return Air for the HVAC. Will there be any issue leaving the blocking out of one joist bay? There is no wall or load other than the floor above it. The load is cantilievered out 16″.
Any thoughts from those that do this regularly?
Jim
Replies
How many joists bays either side of the duct?
What is your joist spacing?
What will your decking material consist of?
Would you considering using a flat 2x at the top of, and in the duct bay only, pocket screwed to the joists each end? You could do the same at the bottom of the joists either side of the duct.
Thanks for the input!
There are more joist bays next to the Air Return, but the return is in the last of the cantilevered LVL's (both sides of the bay). Joist spacing is 19.2". The next 4 bays will be BCI joists. I will have to block those with BCI blocking as they cantilever, too. But it is what it is. Kind of went with the LVL's in the area of HVAC because they are so much more rigid than BCI's. They will also all be hangered on both ends, at the cantilever the hanger will be 13" from the cantilever were the blocking is to go.
The flooring will be 7/8 Gold T&G. Recalculating the space needed, I'm finding a single 19.2 x 9.5" high bay will constrict my airflow too much. So, I will need to minimize blocking in 2 bays. However, it shouldn't need to be a no blocking situaton. I need 154ci of space. Devide that by 2 bays and I need a 77ci hole in each piece of blocking. So, if I put blocking in both bays, but cut a whole in the center of each blocking that is 13" x 6" (inside a 19.2x9.5 space) it gives me 1ci more than I have now. Do you see a problem with this plan?
Jim
Jim,
What you suggest is viable if you use blocking that consists of 3/4" plywood with 2x's top & bottom (flatwise would be fine if pocket screwed to the joists). Cut the smallest hole as practical for your ducts and do the corners of the cutout with a hole saw or forstner bit to avoid any potential over-cut.
Careful layout of this blocking fully coordinated with duct size & location is mandatory.
Good luck.
Sounds good. Thanks you!
I think I may add one more set of blocking to the bays on either side, and then add a couple hangers. That would secure it, and resist rolling, also.
Jim