I’m always surprised at the wide variations in building practices that come up here. So this is something I’m curious about.
On blueprints that come from plan services/books, I often see the note: “Double joists under all parallel partitions”. But I’ve never seen that actually done. The note isn’t on plans that are drawn locally. (At least not that I can remember)
So is that commonly done anywhere? Or is it an old practice that’s gone the way of the balloon frame?
Keep in mind that I’m talking about interior non-bearing walls – Not beams under bearing walls.
I’m a paranoid exhibitionist. I always feel like I’m being watched, but I don’t particularly care.
Replies
What I like to do is spread the 2 joists with a "sub plate" flush with the top and nail it off at the stud layout of the wall above. This gives nailing at the finish floor edges and allows for any holes in the wall plates without compromising any joists.
For plumbing walls I prefer to spread the 2 joists to just clear the toilet drain and insides of wall and build a ladder of 2x4 edge-on-top at stud layout, with a one-size-larger sub plate under the wall. I will set the toilet off-side joist just outside the rough wall framing and support the bowl with cross joist 2x4+2x6 tee braces set so the 2x4 is under the edge of the bowl sides. The 2x6 gives plenty of support for flooring around the drain hole and is not too hard for the plumber to penetrate.
Be an occasional plumber
SamT
I like to use cut-offs or whatever and just put blocks every 19.2 inches between the joists where a partition will fall.
Gives something nice to nail to and doesn't interfere to much with mechanicals.
It is even a good idea to move any jursts that wil fall directly under a wall that will contain plummin or heat or big wires.
No need to give the subs an extra reason to butcher framing.
Some times I go to 19-3/16" spacing but only if I'm using drywall screws or cutting truss members.
Mr T
Do not try this at home!
I am an Experienced Professional!
that is pretty standard in the chicago suburbs.
I will double up the joists but offset them so they just catch by an 1 1/2". My plumbing walls are always 2x6 which leaves 4" for a 3 1/2" drain.
The 2" left on a 2x4 wall is plenty for the electrician and the only time the tinman needs space on a parallel wall is for a cold air return cutting the top edge on a 45 degree angle prvides him with the air-flow he needs.
If you don't put these joists in over time just the weight of the drywall will cause the plywood to deflect a good 1/4".
This really becomes a problem if you have one edge of a swing door against that area .
Only one side drops and the door binds enough that you will have to rehang it.
Boss,
I've always layed out the wall 3-1/2" and mark a 1/4" on each side of the 3-1/2" mark giving me 4" and then nail a joist on those marks and that gives room for all Plumbing and HVAC.
Joe Carola
That is how I used to do it until I ran into an inspector who pulled out the blueprint , pointed to the notation and said " The plan says under the wall not next to the wall"
I could not convince him otherwise and ended up sqeezing one in under the wall and between the 2 allready there.
Not fun for me or the plumber who had to reroute his main stack.
I built a house with doubled up joist under non-load baring walls about 30 years ago.
In more recent days I purchased a house and wanted to tile a bathroom. I found the floor taking a dive toward one wall by a full 1/4". I went to the basement to discover the non-load baring wall setting clear between two joists, sitting only one 3/4" ply.
At least one joist would have been nice to see. I say just double it up, I have got $20 for a joist.
JMHO.
Boss -
Everything I've ever learned about framing, which ain't a whole lot to be honest, none the less says double joists under every partition. I was shocked when I started tearing into our 'new' place to find actual *bearing* walls landing on the plywood subfloor between joists on both the second and first floors of this place. Even one wall, which judging from the let-in bracing was designed as a shear wall, had no floor framing under it. That one took the better part of a day figuring out how to get 2x10 joists under it to support it properly.
On the other hand, this house was built in the mid 70's and is still here and for its age, fairly plump and level. So .... who's to say. But I sleep better after putting the additional framing in.
Dennis in Bellevue WA
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