"Stick Built," "Engineered Trusses," and Load Bearing Walls

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I guess it goes without saying I'm not an engineer or contractor. A friend who's an unbelievable DIYer asked me if a (small) bathroom wall I plan to tear down is load bearing. I couldn't answer. He asked if my home is stick-built and if the attic has trusses.
I changed the subject.
I searched for "trusses" on Firefox and found a great site from some Canadian truss company. I do understand what a truss is, but what I don't understand is why a home built with "engineered trusses" should have anything to do with whether I tear down a measly 6 or 7 feet of (joist-perpendicular) wall.
Anyway, would I *ever* appreciate some dialogue here on these subjects. I don't even really know what I'm asking, although from my research I realize that if a particular attic joist ends on the measly wall I want to tear down, that wall can't be torn down because it is therefore load bearing.
Well, if anyone understands this, please post on why people ask if you have engineered trusses when the subject is demolition of a measly wall. :)
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snipped-for-privacy@yahoo.com wrote:

Engineered trusses are kind of particular about how they are supported. They can't handle something they were not engineered for. A joist wall perpendicular to the joist may well be load bearing and removing it could be a very serious error.
You will not be able to find good information on the web or in this or any newsgroup because you need someone with a good engineer's knowledge to take a look at your specific application and advise you.
--
Joseph Meehan

Dia duit
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Unless you know that the Measly 7 ft wall isnt critical get a pro out, and you dont know. It is not paralel to the joists, so its likely holding something up.
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No expert, but a "traditionally" constructed roof needs some type of support in the form of a beam or Load-bearing wall in the house.
Support for a roof built with engineered trusses comes from the "sides" of the house, and is distributed that way, so you wouldn't need a "load-bearing wall" in the house.
A caution, I am not much of a carpenter or builder. Just repeating what my contractor told me when he build an addition to my house that included engineered trusses.
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In article <1143504045.091993.155540
says...

Not always.
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Couldn't prove it by me...that's why I noted the caution. :>0
As others have said, get someone who KNOWS before you go ahead.
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...

...
I'm not sure why you would feel so sure that's not load bearing. It may very well be, when you consider that if supports ARE used, they will occur at either the center or, often, the 1/3 marks of a span. Even if it's a short wall, you still don't know what's hidden on top of it, as in some spanners that for farther than the wall does.
It "probably" isn't load bearing, maybe, but then again, "maybe" it is. The danger is in doing the "testing" of removing it ;-).
I'll be curious to hear what others say to this last point, but ... I've been told that in some houses, especially those that have suffered remodels, non load-bearing walls have inadvertantly become load bearing and thus removal could be an iffy situation.
FWIW,
Pop
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snipped-for-privacy@yahoo.com ( snipped-for-privacy@yahoo.com) said...

Stick-built roofs tend to only span about the same distance as floor joists and would require load-bearing interior walls to support them.
Engineered trusses tend to be designed to span from exterior wall to exterior wall.
We built our own home and it is about 33' wide. The first and second floors have 13.5', 9', and 9.5' spans (add the 6" per bearing wall and each exterior wall you get 33'!). The roof trusses span the WHOLE distance.
In fact, most of the partition walls are steel stud walls and were installed after the roof was in place. Almost all of the second floor was ONE large room when the roof was first finished! Talk about open concept! ;-)
We did install one partition wall made of wood in the back half of the house near the centre to provide support when the trusses were first craned up there and placed on their sides, but it provides no bearing support for the trusses once they were installed upright.
--
Calvin Henry-Cotnam
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Calvin Henry-Cotnam wrote:

I like that "tend to be" Readers be sure to read that part carefully. As they all are not. I would suggest that "Engineered trusses are designed to span from load bearing surface to load bearing surface.
--
Joseph Meehan

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Joseph Meehan (sligojoe snipped-for-privacy@hotmail.com) said...

But isn't that statement true for ANY type of roof?
The question, of course, is what are the load bearing surfaces?
It is safe to say that the outside walls are, but it is not always obvious just what other walls are.
With our house, the back half of the house has trusses that span the full width, but the front half is two different sets of trusses since the slopes differ at the front due to a room above the garage that is lower (you can see some photos of the roof work at http://newhome.daxack.ca/Photos/Roof ).
It is fairly obvious, probably from just looking at the exterior, but definately from looking in the attic, that there is a bearing wall separating the two front halves. It is not so obvious that there is one wall about 5' long that is a bearing wall that extends from an outside wall in a direction that is perpendicular to the trusses above. It can be seen in the photos near the bottom, labelled "Viewfrom front bedroom".
--
Calvin Henry-Cotnam
"I really think Canada should get over to Iraq as quickly as possible"
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said...

A lesson learned about trusses. Even though they are designed to span the whole distance this is not without some flex. This is what happened to me.
36' wide house, trusses designed to span the whole width. The problem was caused by the fact that there ARE other support walls. The only spot in the house where the trusses actually span the whole width of the house is about 4 ft wide, after about 8 years the ceiling there cracked. The crack was repaired and it would actually stay closed for a year or two. Final fix was made by fabricating a beam out of plywood and 2x8 to span from the trusses that were suported by the interior walls across those that were not . These trusses were fastened to the beam with metal straps and the crack repaired for the last time.
Beam is in the attic and the trusses hang from it.
If the interior walls had been built so they did not support the trusses there probably would never have been a problem.
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Sounds like you have an odd shaped house.
It's fairly typical that truss ceilings will "lift" off interior partition walls on a seasonal basis. So, "floating" the trusses doesn't always work either.
There's a variety of tricks required to avoid such problems.
--
Chris Lewis, Una confibula non set est
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Thanks for the explanations!
David
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The problem is called "Truss Uplift" and is mainly a concern in colder climates. What happens is that during the winter, the bottom chord remains relatively warm as it is burried in insulation (e.g.: the trusses in our house have bottom chords mainly made of 2x5 stock - yes two by five - while the insulation is at least 14" deep).
The other members of the trusses are up in the cold and they tend to contract in the cold. This contraction has an upward force on the bottom chord. This can lift the bottom chord, and your ceiling, away from partition walls.
Our partitions are framed with steel and were done AFTER the roof was in place. For steel, the top chanel is attached to the ceiling structure, which was a concern for the second floor as the trusses span the entire 33' width of the house. Our method was to use two channels: one attached to the bottom of the chord, and the other attached to the studs. The stud channel was inserted into the truss-attached channel. This provides lateral support while allowing truss lift to not damage the steel stud walls.
This does not prevent any gapping of the drywall between the ceiling and the walls, but after three winters we have no visible cracking in those joints. I suppose our trusses have been designed to minimize uplift.
--
Calvin Henry-Cotnam
"I really think Canada should get over to Iraq as quickly as possible"
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Is the wall in line with other walls, like the sides of a hallway? Is it on top of a wall in the first story? If yes it is providing support. Whether the support is necessary should be determined by a structural engineer.

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Jeff wrote:

Yes, it's in line with the side of the hallway. Since this is a ranch home (with what--thanks to you guys--I now realize is definitely a "stick-built" roof), there's no second floor.
The 10 X 10 square that forms the bathroom area of the blueprints (main bath + 1/4 of the sf for a powder room) is about 8' away from the main hall load bearing wall, so Mr. Meehan's theory of "thirds" seems to hold here...*except* that none of the bedrooms on the opposite side of the hallway, nor the living room, have any such "third" partition walls.
Ha, now that I think of it, the ceilings *are* sagging a little in the bedrooms! Anyone have any surplus pillars they want to sell?
But you guys not only taught me some good lessons but convinced me not to even think of getting out my reciprocating saw. Give a girl a reciprocating saw and there's no telling what she won't tear down :) I almost tore down the load bearing wall of a four story home I owned when I was younger, so if you all have daughters--never give 'em a Sawz-All without an engineering lesson!!!
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Your friend is trying to make an educated guess as to whether the wall is load bearing. On the top floor under a full truss roof, interior walls will tend not to be load bearing. In a rafter style roof, interior walls have a considerably higher likelyhood of being load bearing.
(See Henry's posting).
But neither way is a certainty.
The only way to be sure is to have someone know knows what they're doing taking a look in the attic.
--
Chris Lewis, Una confibula non set est
It\'s not just anyone who gets a Starship Cruiser class named after them.
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There's really only one way to find out. Climb up into the attic and see what's resting on top of the wall, then climb down to the crawlspace/basement and see what that wall is resting on.
If the wall is running parallel to the ceiling joists or floor trusses, it's not load bearing (unless you see something in the attic resting on top of the wall). If the wall is running perpendicular to the joists/trusses, you'll need to investigate further.
If the wall is truly a bearing wall, the wall will be transferring that load to something UNDER the wall. If you only have floor joists under the wall, it's unlikely it is is load bearing. If you have a beam or support wall in the crawlspace running the same direction under the wall (or offset a foot or two either way), there's a good chance that wall is supporting some kind of load.
If there's a door in this wall, another indicator would be to check the framing in the wall above the door. Bearing walls will need a header above the door, where partition walls are typically framed without a header. You could check this with a studfinder to see what framing is inside the wall above the door. Having a header doesn't necessarily mean the wall is load bearing (I put headers over all my doorways, even when they weren't needed), but if the header isn't there, it's unlikely it is bearing any weight from above.
If you have any doubts, hire a pro to come have a look!
Anthony
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Sounds like your super-DIY friend might like to help. Next time, say "well, what do you think?" and see if he can offer something helpful.
A competent DIY should be able to take a look at the framing, the joists, walls, etc., and decide if the thing is possibly load bearing, and to what degree. A bathroom wall even if perpendicular might be extraneous. Or, of little enough value that just adding a short beam with two posts (hidden in the adjacent walls) would be enough to take care of the floor above. But noone can tell frome here.
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kevin wrote:

Funny, I was just watching one of those "Re-Bath" commercials. The had a traditional bathtub surrounded on either end with pillars!
Anyway, in regard to the double-plate for the door header, my feeling is that whether mine has a double plate or not, from what Pop (?) said, the way the ceilings are sagging on the half of this ranch house that has *no* supportive walls, I tend to think that these mini-walls in the bathroom have more than done their job in keeping a similar problem from developping on that side of the house.
Hey everybody, thank you all VERY much.
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