Moving a [possibly bearing] knee wall.. little help here..

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Hey y'all..
I'm working on an old 1 1/2 story house with a finished upstairs/ attic. The "knee walls" (if you can call them that) are rather tall (close to 6') and a lot of space is wasted behind them. The plan is to build a large closet that utilizes some of that wasted space behind the wall, but also extends (minimally) out into the room.
Here's the problem I'm facing. I'm worried about disrupting any load that the knee wall might be carrying. I'm pretty sure it's not designed to be load-bearing (I very well could be wrong). Why do I think that? Well, there is no top plate (let alone two) between the knee wall studs and the rafters. Also, while the knee wall runs in the same direction as the load bearing structures on the main floor and the basement, neither the knee wall I'm working with, nor the one on the other side of the room, are aligned over the load-bearers on the other two levels.
The knee wall studs are cut off at angles and attached directly to the underside of the rafters. They all sit quite snug between the rafters & a single bottom plate, and run the full length of the house/ upstairs. Obviously the movement/weight of the roof (add in wind, snow, etc.) is a load that these studs are dealing with. How much of an issue will it be to move the support of this section back about 2'?
The closet being built will open up about 8' of the knee wall's original stud support and will occur close to the middle of its run. It will come out from the wall at almost 3' and recess into the wall a little over 2', where the new joist-to-rafter wall will be built.
Am I over-thinking this or should I be concerned about some load shifting here? If "moving" the wall isn't much of a problem causer, how would you go about constructing that new closet back wall? The same way as original, with the studs attached directly to the rafters and a sole plate? An angle cut 2X6" top plate between the studs and the rafters? No angle cut, and just a 2X4" top plate with a gap in the rafter-top plate-stud connection?
I'm sure I haven't explained this very well and would be happy to clarify anything I've left out or have a different name for than someone else in another part of the country. So please ask.
Any help at all would be greatly appreciated.
Thanks. Holden
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I think I'd try to build a header (2X8s? 2X10s?) to go under your new kneewall studs assuming you can provide enough load bearing on both ends. That will mean a "step-over" to access the closet but would address your load issues.
--
Dave in Houston



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On Aug 31, 4:14 pm, snipped-for-privacy@gmail.com wrote:

Look at the size, spacing, and span of the roof framing. Check the roof covering for weight. There are several online tables that give appropriate spans. Snow load, wind load, and seismic load must be considered too.
For a small fee, you could get a structural engineer to look at the situation and make a proposal. It would be cheap insurance.
T
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It's almost certainly not a structural wall. Generally what one would expect to see in an attic that would be considered as structural are purlin support braces. They would intersect the rafters at 45 deg and be tied to the attic floor over a continuous, load bearing partitions on the floor below.
One way to estimate as to whether the rafters would need any additional bracing is to look at their size (grade and species if you can find the stamp) and at their span and rafter slope. Then a quick check in a model code (such as the IRC or UBC) and you should find they are sufficient. (If you don't have a model code post the data here & we can look it up for you.)

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It certainly could be a load bearing wall. The fact that the studs are directly under the rafters might be a clue. Modern engineers probably wouldn't let you drop a load bearing wall on to floor joists with no bearing wall underneath, but I have seen such things in old buildings. Speaking of modern engineers, it's likely the whole roof is underframed by today's standards. If you ask an engineer, he's liable to have you sistering on 2x12's on your rafters. Your lumber is also highly, highly unlikely to have grade stamps, if it is old as you say. What do you want? If you want to bring the roof framing up to modern codes, then call an engineer and be prepared for some big work. If it's your house, and if it is working now, I'd guess you could move the wall two feet. But it's just a guess. No guarantees.
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holden.mccrank> wrote

Those studs are acting like vertical members in a truss and are transferring some of the load from the top chords to the bottom chords. Further, with the bottom plate it is spreading the top chord load across the bottom chords. If you are to remove this *wall* you should find another way to transfer the top chord loads. I'll suggest you build a header along the face of the studs, right under the top chords, and then cut the studs out. However, the ends of the new header will now be carrying a concentrated load which you will need to transfer to a load bearing wall below, or a new post/column. Without seeing the actual scope of what you're doing, you should hire a local specialist to evaluate the whole thing.
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Ok, a little more information (that I should have listed already), in addition to my original post:
The rafters are 2X4s, without a grade stamp. The rafters are spaced 16" OC. The roof slopes at a 45 angle. The full span (from the outer walls to the roof point) is approx 18'. The current knee wall occurs in the middle of that span at approx 9'. Over the rafters (under the shingles) are planks that are 7 1/2" wide and 3/4" thick. The planks run the length of the house (across the rafters). On top of the planks, looks to be wood shingles (??). Covering that layer, is likely a couple asphalt shingle jobs.
Hope this helps paint a better picture. Thanks for the input so far. BTW, how much would it be to get someone out to evaluate this? Ballpark figure is fine. I'd like to get this started, but from what I've heard so far, I wasn't wrong in thinking this could develop into a much larger problem. So, doing it the right way and getting a specialist to take look, probably would be wise.
Thanks again, and if there's more info I could provide, please ask. Holden
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Hard to say without seeing it person, but from your description (3/4 deck, plus wood shingles, plus multiple layers of asphalt), I'd put off the attic remodel in favor of a roofing tear-off and replacement. Even if these are old-style 'real' 2x4s (my assumption from the wood shingles), that is a hell of a load for 2x4s spanning 9 feet, even at a 45 degree angle on 16" centers. Can you see the wood shingles from underneath, through gaps in the planks? (aka 'skip sheathing') How old is the most recent roof? How old is the house? Are there any side-to-side collar ties above the level of the knee walls? Any gussets or blocking where the rafters meet the ridge beam? <Something> is needed on a 12-12 roof like that to keep it from pancaking. (gravity never sleeps, etc.)
Another advantage of a tear-off - if your remodel plans include any dormers, it is a lot easier to cut those into a bare deck.
I agree with the others, and with how it sounds like you are leaning- a site inspection by a professional engineer or or experienced designer is called for. Cost vary greatly by area, but the residential designers, at least, will usually do an initial walkthrough at little or no cost, and tell you how much they would charge for working drawings good enough to get stamped by the permit office. Some areas require architect's stamp for residential, some don't. An old roof may be grandfathered under code, but some augmenting of the structure sounds like it may be called for.
aem sends...
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On Sep 1, 4:39 pm, snipped-for-privacy@gmail.com wrote:

Yes, that is a stretch for 2x4's. But it's not uncommon in old houses. I think you can be fairly sure that the knee wall is serving as a bearing wall. I will revise my earlier post and say that you shouldn't really touch anything up there unless you are prepared to some fairly major structural work. Go ahead and call an engineer, but only if you are prepared to do a lot of reinforcing--it's really unlikely he would tell you that you could move that wall.
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In a previous post marson wrote...

I second that notion. Most old houses will not calculate for today's design loads. Unless you are prepared to do a lot of work, I would just leave it alone.
--
Bob Morrison, PE, SE
R L Morrison Engineering Co
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Bob,
I see this so often, an old place with 2x4 rafters spanning 12' or more . Many times there are 2 and 3 roof layers and the rafters are not noticeably bowed, stressed, or broken. The roof tends to feel rock solid when walking on top.
These things can't make current code, yet they stand just fine. Are codes over built? Was the old lumber that much better? ______________________________ Keep the whole world singing . . . . DanG (remove the sevens) snipped-for-privacy@7cox.net

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DanG wrote:

...
Some of both...
Much of older lumber was "old forest" growth which is typically tighter grain that the "plantation grown" present construction lumber. Also, if it is roughly 50s or earlier, dimension lumber was somewhat larger in cross section (the 1-5/8 finished vs 1-1/2 for 2x stuff) and if it was earlier even larger or occasionally roughsawn was nearly full dimension.
--
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You are also much more likely to see doug fir 2x in old houses-- something you rarely see except in 2x10's and 12's in lumberyards where I live these days. Most 2x4's I see are spf (spruce-pine-fir). I was looking at a unit of 2x4's the other day where every single one had at least part of the pith of the tree--meaning that they are cutting them out of very small trees. I don't think they are necessarily second growth trees, because the growth rings are pretty tight. A lot of spruce, jackpine, and true fir from canada. 50 years ago, I think that noone in their right mind would have dreamed of making framing lumber out of those kind of trees.
At any rate, I think carpenters were also much more likely to push the envelope in the old days--sometimes it worked, and sometimes it didn't--look how many old roofs sag. I'll bet you our modern roof framing is going to last a long time, if moisture doesn't get it first. I'm working on a 90 year old house at the moment, and the old saw "they don't make them like they used to" isn't always true.
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marson wrote:

...
I think that also depends in large part on where one is...in the SE, it would have been a high probability of being yellow pine even 100 years ago, as are most of the buildings here in the area where I am. Even though we're geographically closer to some of the fir forests, the railroads initially didn't extend on west so everything came from the east...
In the 40s/50s, probably that became more nearly 50/50...
We still don't see a whole lot of the Canadian "white wood" except for precuts...virtually all other construction is still SYP and it definitely is virtually from cared-for plantings...
--

--

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Everything in the 1929-built frame house I once owned was early 20th century SYP and it was all 2X4 including the rafters (though there were purlins and considerable bracing to load bearing walls. The point, though, that the wood fiber was so dense you couldn't drive a casing/finish nail less than an 8p w/o pre-drilling.
--
NuWave Dave in Houston



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Interesting about the SYP in the south. Here in the upper midwest In the 90's we were getting a lot of it for structural lumber. Now it isn't so common for some reason--buy a 2 x 12 and 9 times out of 10 it is hem fir or doug fir. I was told the Japanese were buying it, but who knows for sure. Definitely never see it in old buildings. I remember way back when having a lumber yard try to sell me some. I scoffed, but have since learned that it is actually stronger than doug fir.
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I think the "some reason" may have to do with tariffs and trade agreements. I seem to remember lots of bitching from American producers about the breaks given Canadian lumber. I know from my years working for the railroad that we handled lots and lots of lumber that crossed the border up in the northwest.
--
NuWave Dave in Houston



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Dave in Houston wrote:

It does get hard w/ time, that's true... :)
House/barn/elevator/etc. here all from 1910-mid 20's and all SYP. House all 2x4 (almost full-dimension smooth surfaced), barn is mostly 2x6 and 2x8. The haymow columns are 4 2x8's nailed, 24-ft long to the gambrel ridge. Most of them are knot-free. All are very close grain and besides that the pitch when fully dry as it gets w/ time adds to the hardness.
When doing the new roof and restoration, found some old left over Doug fir from the new construction we did in the late 50's to add a feed mill and overhead bins/elevator leg/etc. About 2-dozen each 2x10 and 2x12 20-footers. Most of them are clear as well, w/ just a couple with a small knot or two. I wonder what it would cost to replace one of them now! :)
--


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(snip)

You are so right about common lumber back then, versus common lumber now. Scraps and cutoffs I threw on the burn pile as a kid, I would take home and stash now, for small projects and spot repairs. Who knew? I think we have cut all the easy good lumber in the lower 48, and I'm not sure how much Canada has left. One of these days the old east block countries will realize what a gold mine they have in all those old-growth forests in their undeveloped areas, or even in the areas that were basically abandoned for fifty years because the USSR couldn't get their act together. Baltic states have patches of old farms that basically were ignored from WWII to the mid-90s- some of those old woodlot trees are looking rather respectable. When I was over there, I saw truckloads of timbers that made me drool- the metric equiv of a 4x12 or so. They were making freaking pallets out of them.
aem sends...
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When I originally read your post, I assumed a form of construction completely different. However it would definitely not a knee wall. It appears to be a system of braced rafters (2x4's spanning 18' is way below practice without bracing). I agree with marson and Bob that it might be better to leave the supports alone. (Sorry for not seeing a better picture of this.)
However, it still may be possible to add a closet space behind the supports; but to do so would require the services of an engineer as you will need to design a header and columns to offset the cut support(s). As long as the closet door was kept small, 30 inches or less, the header would be framed like any bearing wall carrying roof load & would most likely be minimal. But it would have to be engineered as no model code has specific provisions for this specific type of constriction (at least none I'm aware of) and it's unlikely the local code official would by off on it with out a PE calc. An additional consideration is whether the attic joists are heavy enough to carry the added storage loading. Again, a local engineer would be able to quickly analyze this for you.
The rafters are 2X4s, without a grade stamp. The rafters are spaced 16" OC. The roof slopes at a 45 angle. The full span (from the outer walls to the roof point) is approx 18'. The current knee wall occurs in the middle of that span at approx 9'. Over the rafters (under the shingles) are planks that are 7 1/2" wide and 3/4" thick. The planks run the length of the house (across the rafters). On top of the planks, looks to be wood shingles (??). Covering that layer, is likely a couple asphalt shingle jobs.
Hope this helps paint a better picture. Thanks for the input so far.
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