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Floor framing. Why put a joist under a non-loadbearing wall?

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Willin

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Discussion starter · #1 ·
Plans often are drawn that show, in the floor joist layouts, off-layout extra joists located under nonbearing walls that run parallel to joists.

When I draw plans, I locate joists under bearing walls only for parallel walls off-layout, but I do it with two joists spaced apart the depth of wallplates above. Thus for a 2x4 bearing wall, two joists are below spaced 3-1/2 apart, directly under. Makes the plumbers and electricians smile.

But for nonbearing walls, why do any extra joists at all? I just make a note to have the framers scab in some cross-cats at 16" centers. That wall above is not going to deflect the floor, and all that is needed is nailing for the plate.

Why not? Just looking for alternative ideas.
 
#2 ·
One reason is to carry the extra dead load of the non-bearing wall. There is the added weight of the framing and the drywall and and anything that might be hung on the wall.

Makes sense to me, a little extra insurance to make sure the floor does not deflect over time and not a big extra expense.

Also it ties into the floor and roof diaphragms (somewhat incidentally) for wind and seismic bracing. Probably not a part of the braced wall lines but helps none the less.

Andy.
 
#3 ·
As a framer, none of us would prefer cutting a pile of solid blocks as opposed to one joist, much less take the time to install them.

As stated above, it carries the additional dead load of the wall and all of its components.
 
#4 ·
loneframer said:
As a framer, none of us would prefer cutting a pile of solid blocks as opposed to one joist, much less take the time to install them.

As stated above, it carries the additional dead load of the wall and all of its components.
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Exactly. Much cheaper than having a guy fill in blocks. Add joist when framing floor structure and you're done.
 
#5 ·
Non bearing walls get no extra framing from me.

I actually make an effort to avoid having them close to the joists.

The last few years all of my designs Have so few walls.

The subs need all the wall and joist space below they can get.
 
#6 ·
Where are you located? Around here doubled up joists are specified under sheer walls a lot, with nailing patterns and or straps that go through the floor, no load bearing just sheer. If its not a load bearing or sheer wall then I don't see why you need it either. But if you leave it out, your inspector can still make you put it in if its on the approved set of plans.
 
#11 ·
TimelessQuality said:
What if there's plumbing in said non-load-bearing wall?
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It depends on the situation, but wet walls typically get a joist set just to the outer edge of the wall so there is full access from the wet side, preferably a 6" wall for ample space to accommodate waste lines and fittings.

The joist still shortens the span between layouts and stiffens/strengthens the floor system without creating issues with the plumbing.

Considerations should also be taken on walls that will ultimately accommodate cold air returns, HVAC feeds or other types of mechanical equipment.
 
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#12 ·
I see what happens when people have good ideas from time to time. When I go in to cut out the floor and there isn't support for a non-loadbearing wall, I have to cut out the ceiling below and install some blocking. 2 minutes of framing work that was skipped turned into demo, framing, and finish work. Not to mention if the wall needs to be made load bearing at some future date. On the other hand, if you're building a throw away house that'll be torn down in a few decades, why not?

Does anyone really think this non-load bearing wall is going to stay where you put it, and not sag just using subfloor?
 
#13 ·
loneframer said:
It depends on the situation, but wet walls typically get a joist set just to the outer edge of the wall so there is full access from the wet side, preferably a 6" wall for ample space to accommodate waste lines and fittings.

The joist still shortens the span between layouts and stiffens/strengthens the floor system without creating issues with the plumbing.

Considerations should also be taken on walls that will ultimately accommodate cold air returns, HVAC feeds or other types of mechanical equipment.
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They're even worse than plumbers. :whistling
 
#14 ·
When I draw plans, I locate joists under bearing walls only for parallel walls off-layout, but I do it with two joists spaced apart the depth of wallplates above. Thus for a 2x4 bearing wall, two joists are below spaced 3-1/2 apart, directly under. Makes the plumbers and electricians smile.

More suprising to me, is the myth that bearing walls can always be supported by just throwing in a couple of extra joists under the walls. The common joists may be spanned to their max carrying a 16" strip of floor load, so how are two of the same joists going support a bearing wall?
 
#15 ·
Bearing or none bearing, I always use a double if that wall span is the whole room length or if there is a certain situation. Non bearing partitions which run perpendicular to floor ceiling framing do require extra floor framing per 2009 RIC R602.10.6(1) if there is a framing member located above that partition.
Like Andy and Lone said, floor joists must meet strength and stiffness requirements. Strength requirements depend on the load to be carried. Stiffness requirements put an arbitrary control on deflection under load and let's not forget that
Stiffness is also important in limiting,that bouncy feeling when you walk or vibrations from moving loads,etc. Especially when you have a partition span the whole length of the room and heavy furniture is placed against that wall, or there could be a tub sitting on the other side of the wall, a few kids jumping up and down,etc... not having that extra support, it will make that floor bounce like a trampoline.
With that said, even if not a requirement...what are we talking about here... a few pieces of extra lumber that will make a much better floor system... I think its worth having it.
 
#16 ·
greg24k said:
With that said, even if not a requirement...what are we talking about here... a few pieces of extra lumber that will make a much better floor system... I think its worth having it.
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Few extra in the floor, few extra in the roof, few extra in the walls, before you know it you've added $1,500 and if every trade just adds "a little bit" you'll have added 25k before you know it.

Not that I disagree at all but I have this discussion with hos all the time. Them "well why didn't my builder do it like that to begin with?" Me "Would you have paid an extra 20k for your home for all these little things that you wouldn't know or notice when looking at your home?" Them "I would now, but probably not back then." me "now you know to call me for a custom home when you're ready to move."
 
Discussion starter · #17 · (Edited)
greg24k said:
Non bearing partitions which run perpendicular to floor ceiling framing do require extra floor framing per 2009 RIC R602.10.6(1) if there is a framing member located above that partition.
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I read that to apply to braced walls, not just ordinary interior partition walls that are not shear walls. Braced walls need to pick up shear resistance from their connections at floor diaphragms above and below, thus that piece of code language.

That's not what we are talking about here.
 
#18 ·
RobertCDF said:
Few extra in the floor, few extra in the roof, few extra in the walls, before you know it you've added $1,500 and if every trade just adds "a little bit" you'll have added 25k before you know it.

Not that I disagree at all but I have this discussion with hos all the time. Them "well why didn't my builder do it like that to begin with?" Me "Would you have paid an extra 20k for your home for all these little things that you wouldn't know or notice when looking at your home?" Them "I would now, but probably not back then." me "now you know to call me for a custom home when you're ready to move."
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Just a few hundred Rob if that on the whole house... 25-30k is about the whole lumber package to build a 2,500 SF home including lumber, windows and framing and have enough change left to take a few week trip to Florida :thumbsup:.
I don't know what you pay for lumber, but my cost on 2x10-16' is around $10 -12. so if you have in a house 10 partitions which span a substantial distance that I would double up the joist... we're talking about $100 give or take and giving 10 partitions is being generous... My house is about 4,500 SF and I have 3-4 partitions where I doubled up the joist. It's nickel and dime stuff.
 
#19 ·
greg24k said:
Just a few hundred Rob if that on the whole house... 25-30k is about the whole lumber package to build a 2,500 SF home including lumber, windows and framing and have enough change left to take a few week trip to Florida :thumbsup:.
I don't know what you pay for lumber, but my cost on 2x10-16' is around $10 -12. so if you have in a house 10 partitions which span a substantial distance that I would double up the joist... we're talking about $100 give or take and giving 10 partitions is being generous... My house is about 4,500 SF and I have 3-4 partitions where I doubled up the joist. It's nickel and dime stuff.
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Try actually reading my post... I said if EVERY trade adds a little here and a little there, framing is not the only trade in the world.
 
#20 ·
RobertCDF said:
Try actually reading my post... I said if EVERY trade adds a little here and a little there, framing is not the only trade in the world.
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Rob,I know what you said, but the OP is not talking about other trades. The question is about flooring system. As a GC, my job is to make sure the structure is built right... and being that a joist or adding an extra light if I feel it needs one, or adding extra concrete to make a footing stronger... money at this point is my last concern.

I'm sure when you doing a deck estimate and you can get away with a
2X8 for the span you have, but that 2x8 would be close to the max of that span length, you would change to 2x10 even if it cost you $100 more.

With that said Footing, Foundation and Framing are the most important elements of the structure and that is the last place anyone would want to worry about adding an extra joist or a stud if a framer or GC feels it needs one.
 
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