Supporting row of bookcases between open truss joists
oquest
| Posted in General Discussion on
I’m looking to put a row of 5 (full) bookcases along a wall in a 2nd floor bedroom. The wall is parallel to the floor joists and sits directly on top of a joist. The joists are 24″ apart, so the bookcases would end up between joists. I estimate the total weigh at 1500 lbs with a 11′ x 1′ footprint. I will be having hardwood floors laid down next month (4″ wide planks, perpendicular to the joists) and the current subfloor panels are APA 23/32″ OSB, which are rated to support a partition load at 126 lbs/ft. At minimum, I would like to replace the subfloor along the wall with APA 48/24 sheathing panels, which support 173 lbs/ft. Since the one joist is beneath the wall, I believe I would need to add bridging/blocking between the joists to attach the subfloor and also to have the added weight support. Since the joists are open truss, I was thinking of using face mounted joist hangers. However, I’ve read that bridging between open truss joists is not recommended. (Specifically, they are 16′ long, 2×4 chords, 11 7/8 deep, wood is 2100f/1.8E, unknown manufacturer – the house was build in 1989). I would like the bridging for the support, but if it’s to be avoided, is the only solution to cut out part of the wall at the bottom and attach to the joist there (with notches in the panel for the studs). Any suggestions/recommendations would be greatly appreciated.
Replies
1. talk to an engineer. may be the cheapest way to avoid unnecessary work.
2. load path below the joist isn't explained in the post. open span at the 1st fl ceiling is different from partition wall below.
3. replacing sheathing may make condition weaker since it usually spans under the partition wall. typically need to offset joints in floor sheathing.
4. dumb way is to add a lvl under the wall to take load, including any supports to take point load down to foundation.
5. crazy way would be to turn the wall partition into a shear wall and make cabinets super strong and hang them off the wall.
6. if you want to do the research with the manufacturers, then figure that there weren't many companies making open truss joists for residential in the 80's. look at old FHB to see who was advertising back then. also support for an open web truss today won't be much different than it was 40 years ago.
7. talk to an engineer.
Thanks, was trying to get in touch with an engineer, but no one was getting back to me. Finally got a reply today. In any case, there's a 1st floor wall directly under the 2nd floor wall and yes the subfloor panels span under the wall. There was one part that was replaced at some point in the past (see photo).
You are over thinking this. In 50 years of construction I have never heard of an engineer being consulted for the placement of residential furniture. The average book weighs about 8 oz. Assuming an average thickness of 1", that's 3000 inches of books. That's 250'. That's more than twice the amount of shelving you are planning on. Residential floor loads are usually figured at 50 psi. But that doesn't you can't put more than that in one place. That's
for the whole floor. Assuming that 2' in front of the bookcases will have no load except when someone is standing there, your floor will easily support the intended loads. Don't. worry about it.