Thread: Knee wall support

This is most likely adequate, but I don't like the way it looks. Floor joists are spaced at 16" on center. Studs below at knee/pony walls are spaced a 24" As you can see in the photo the knee walls are double plated on top.

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I don't see anything wrong with it. I'm assuming your concern is that there are not studs directly beneath every joist? Rafters bear between studs all of the time, which is why a double top plate is required. That's a pretty common installation in this area.

Thats what I thought, I just don't usually see 24" spacing on knee walls. Seems like a stupid way of saving a few dollars.

Some are may require ply-wood shear panels.

In Ca. thats a big issue.

Best

Ron

It looks like a load bearing wall.Studs should be under the joists,if load bearing.Look at the framing in most houses,studs over joist,joist over studs,load goes to foundation.Standard practice.The building in the picture is not going to fall down but there might be a little bounce depending on the load above.

A closer look at the picture reveals engineered lumber for the joists,which can span greater distances than regular lumber.Maybe the knee wall is just absorbing the bounce and is not critical to the structure.There is blocking in between the joists.Is there a bearing wall above?If so, joists over studs.Check for plans at town hall?
Looks like a commercial building.

Yes they are engineered I-joists. And no it's not a commercial building. This is how most of the new homes in my area are being built, except for the 24" spacing on the knee walls.

Is there a load bearing partition above?

No there is no load bearing wall above.

This may help...
First define what your dealing with... a load bearing wall...

And, just to be sure...

WALL, LOAD-BEARING. Any wall meeting either of the following classifications:
1. Any metal or wood stud wall that supports more than 100 pounds per linear foot (1459 N/m) of vertical load in addition to its own weight.
(The second classification is for concrete...)


Now how that wall should be built...
A load bearing wall can be no more than 8 feet... (I contend, studs on a sill plate constitutes a wall...)

IBC - 2308.9 Wall framing.
2308.9.1 Size, height and spacing. The size, height and spacing of studs shall be in accordance with Table 2308.9.1 except that utility-grade studs shall not be spaced more than 16 inches (406 mm) o.c., or support more than a roof and ceiling, or exceed 8 feet (2438 mm) in height for exterior walls and load-bearing walls or 10 feet (3048 mm) for interior nonload-bearing walls.


So, uh... wadda ya think? Too far apart?

Originally Posted by Bob Phoenix

This may help...
First define what your dealing with... a load bearing wall...

And, just to be sure...

WALL, LOAD-BEARING. Any wall meeting either of the following classifications:
1. Any metal or wood stud wall that supports more than 100 pounds per linear foot (1459 N/m) of vertical load in addition to its own weight.
(The second classification is for concrete...)


Now how that wall should be built...
A load bearing wall can be no more than 8 feet... (I contend, studs on a sill plate constitutes a wall...)

IBC - 2308.9 Wall framing.
2308.9.1 Size, height and spacing. The size, height and spacing of studs shall be in accordance with Table 2308.9.1 except that utility-grade studs shall not be spaced more than 16 inches (406 mm) o.c., or support more than a roof and ceiling, or exceed 8 feet (2438 mm) in height for exterior walls and load-bearing walls or 10 feet (3048 mm) for interior nonload-bearing walls.


So, uh... wadda ya think? Too far apart?

I had to read your comment twice and your reference, you did mean that a bearing wall with utility grade studs can only be 8', right?

Partially...,
The reference is the table and anything but utiliy grade lumber will be spaced according to that table... But, load bearing walls that are made with utility grade lumber can only be 8 feet tall if they are exterior, load bearing walls... or support more than a roof and a ceiling...(if they're not exterior...) or be spaced not more than 16" apart... (in any case...)

Pretty restrictive, huh?

So, if you couldn't find a grading reference on any of those studs... then it must be utility grade lumber and therefore shouldn't be spaced more than 16" apart...

No matter what there should have been a beam and posts or piers or 16 on center 2x under the floor joists.

Doing it the way they did to save a few dollars at best is pretty lame and should tell one of the rest of the structure.

Look at the money spent on the cocrete footer that the wall is on and then they framed the wall like that. Again, cheap and lame.

In addition to the spacing issue, my opinion would include that the system is functioning as a beam (girder) and must comply with:


R319.1 Location required.

Protection from decay shall be

provided in the following locations by the use of naturally
durable wood or wood that is preservative treated in accordance
with AWPA U1 for the species, product, preservative
and end use. Preservatives shall be listed in Section 4 of
AWPA U1.
1. Wood joists or the bottom of a wood structural floor
when closer than 18 inches (457 mm) or wood girders
when closer than 12 inches (305 mm) to the exposed
ground in crawl spaces or unexcavated area located
within the periphery of the building foundation.
2. All wood framing members that rest on concrete or
masonry exterior foundation walls and are less than 8
inches (203 mm) from the exposed ground.

Ideally that sole plate should be pressure treated or isolated from the concrete (can't tell from photo if it's PT . The 2x studs should be located directly underneath the floor joists or offset a maximum of 3" from the joist (45° off center allowed = 3" for double top plate).

But the stud placement issue is pretty easy to fix - simply add studs beneath the floor joists where they're missing. Shouldn't take much more than an hour or two for a competent contractor.

Just to clarify a few points made in earlier posts, the joists don't need to fall directly over the stud as long as there is a double top plate.

Also, the laterally unsupported stud height in that table is for bracing perpendicular to the plane of the wall (such as is provided by the floors). The table assumes that the studs are braces in plane (in teh weak direction) by the wall finishes plywood sheathing, GWB, etc.). In the case shown, there is no sheathing so I suppose that it is not actaully a wall, but just a series of posts.

I agree that if it is a bearing "wall", then some bracing is recommended.

Originally Posted by Steve Frederickson

Just to clarify a few points made in earlier posts, the joists don't need to fall directly over the stud as long as there is a double top plate.

That depends on the loads on that knee wall. What is the span of the room and the allowable span of the floor joists?

Not sure where you're comming from Steve,
The table gives a maximum stud length of a bearing wall, (not a minium) if that stud has no lateral support...
(There's another section that brovides for additional lengths with stud bracing...)

The IBC definition of what a load bearing wall is, is pretty clear...
According to Trents long shot photo, at 24" OC, that wall, (as short as the stud mat be...) is supporting at least 2600 pounds of materials... (100 LBS per linier foot... according to the definition)
Causing a load bearing wall, made with "utility grade" lumber to have a required spacing of not more than 16" O.C.

But, I will agree with you, that the studs do not need to align with the joists...

Bob

Originally Posted by Bob Phoenix

Not sure where you're comming from Steve,
The table gives a maximum stud length of a bearing wall, (not a minium) if that stud has no lateral support...
(There's another section that brovides for additional lengths with stud bracing...)

The IBC definition of what a load bearing wall is, is pretty clear...
According to Trents long shot photo, at 24" OC, that wall, (as short as the stud mat be...) is supporting at least 2600 pounds of materials... (100 LBS per linier foot... according to the definition)
Causing a load bearing wall, made with "utility grade" lumber to have a required spacing of not more than 16" O.C.

But, I will agree with you, that the studs do not need to align with the joists...

Bob

If they're using "utility grade" lumber then you have more problems than just the spacing. My local yards carry nothing less than No. 2.

But, as to whether the studs need to be under joists or not... it depends on the loading. Whether you see it all the time or not is of little consequence. If there is significant load on that wall, and the top plates are in effect acting as a beam, then that beam needs to be sized to support the load. If that beam is undersized then the load needs to be carried directly by the posts which must be placed directly under the joists or offset by at most 100% of the beam depth.

Bob,

I was just trying to say that the maximum unbraced lengths in the table do not apply to studs that are not braced in the weak direction (in the plane of the wall). The table assumes that the wall sheathing is providing that bracing. In this case there is no wall sheathing, so the table really doesn't apply.

With respect to double top plates, I agree that if there is a large point load above then it should align with the kneewall studs. However, in the case of normal loads from floor joists, and conventional framing, the joists don't need to line up with the studs when there is a double top plate.

"2308.9.2.1 Top plates.

Bearing and exterior wall studs shall be capped with double top plates .... Exception: A single top plate is permitted, provided ...the rafters, joists or trusses are centered over the studs with a tolerance of no more than 1 inch (25 mm). '

Trent,

Is that the flexible Owl Flex duct and it is tearing? And if so, it all needs to be replaced, or, is that insulation stapled around metal duct?

What are the odds that this is an engineered design?

Originally Posted by Brandon Whitmore

What are the odds that this is an engineered design?

Does not really matter. With a doubled top plate the trusses, studs, rafters, etc., DO NOT need to be aligned with the studs below.

Think about it a few minutes: Many walls are 16" on center studs with the rafters, trusses, joists, etc., being at 24" on center ... HOW can you get them to "line up with the studs"?

You can't.

Does not really matter. With a doubled top plate the trusses, studs, rafters, etc., DO NOT need to be aligned with the studs below.

Think about it a few minutes: Many walls are 16" on center studs with the rafters, trusses, joists, etc., being at 24" on center ... HOW can you get them to "line up with the studs"?

You can't.

Thanks Jerry,

Read post number 2 on this thread

Hmm, engineered lumber, clearly seen, but no one bitched about the vapor barrier on the insulation? shouldnt it be on the conditioned side?... Again you ar not engineers. state the obvious and move on. BTW nicw references AD and others, if only they were applicable

Your monitor must be better than mine. I don't see any vapor barrier on the unconditioned side of the joists. I do see the wire or string used to hold the insulation in place. Why would they need that if there is a vapor barrier?

Originally Posted by Joe Driscoll

Hmm, engineered lumber, clearly seen, but no one bitched about the vapor barrier on the insulation? shouldnt it be on the conditioned side?... Again you ar not engineers. state the obvious and move on. BTW nicw references AD and others, if only they were applicable

You don't always need a vapor barrier covering the insulation in the floor over the crawl.

Each home needs its own eval.

Just because many may say vapor barriers are needed. Or a code says there is a vapor barrier needed. Or some "expert" says a vapor barrier is needed. It does not meen one is always needed for the particular home in question.

Everyone keeps quoting what should be done. How it should be done. Why it should be done. The book (any book) says it should be done. It does not meen it is the best way to do it in this home or if it will cause more harm than good in this home.

There is no fix all cure all that can be tagged to every crawl.

Back to the original post. I for one think that for the sake of doing the "right thing" in the framing of that knee wall I personally would have taken the extra minutes (literally) and couple dollars more that it would have taken and framed the knee wall with the studs under the floor joists.

Why....then there would not be a bunch of idiot inspectors like me questioning if it should have been done that way for one. It is not like a roof that is framed over 16 on center wall studs and the roof is 2 feet on center ad you could only mathc several studs the length of the wall. If this will tell you anything...the engineered floor joists are 16 on center. Span must be fairly great. Walls have to be buitl on top of this floor throughout the home and then the roof on it. Drop the freeking knee wall stus inder the floor joist and be done with it.

Why....then there would not be a bunch of idiot inspectors like me questioning if it should have been done that way for one. It is not like a roof that is framed over 16 on center wall studs and the roof is 2 feet on center ad you could only mathc several studs the length of the wall. If this will tell you anything...the engineered floor joists are 16 on center. Span must be fairly great.

One thing I find strange is the fact that they could have ditched the 2nd top plate, and used that framing for the extra studs-- it wouldn't have taken much more time, and would have been better. Heck, they even went to the trouble of leaving out a section of strip footing for easier access, and installed a header at this location-- can't say I've ever seen that on this type of install.

Originally Posted by Brandon Whitmore

Thanks Jerry,

Read post number 2 on this thread

Brandon,

I know, but then others said something else in later posts ... just catching your back is all.

Just a little advice to anyone who bought a code book,don't just look at the pictures actually read it.It really should be a requirement that HI have some kind of construction background.How many homes can one man inspect in one year?

It really should be a requirement that HI have some kind of construction background.

MG: This has been my contention for 30 years.

How many homes can one man inspect in one year?

MG: At least 500, assuming that he has no construction background and not a clue as to what he is looking for.

I see,from their websites, some inspectors claim many thousands of inspections over the coarse of 6-7 years.I would think 250-300 would be a good year.

Anyone boasting high numbers like that are doing drive bys. hell I inspected 12 homes driving to the job site today

Makes you wonder what other bull s**t they claim, now I'm not talking AHJ or multiple inspector firms here, we know they do thousands.

If they did two a day, *everyday*, no weekends, no vacations,etc. it would not add up to a thousand a year