2

Part of my roof is made from studio trusses as shown in the picture. I'm trying to determine if any of the load from these trusses is borne by the highlighted wall.

The wall is built with 2x6s, but this may be because it contains a plumbing vent.

The architect has said that any bearing walls would be indicated in the plans, and this wall is not shown as load-bearing. Indeed, in our variant of the plan, this wall doesn't go to the ceiling, being only three feet high. (Edit: to be clear, the plan for our variant of the house shows the wall as three feet tall, but it was built full-height, and with 2x6s rather than the 2x4s shown here.)

Still, it's worrying that these trusses all touch a heavy wall that goes all the way down to the slab. Can anyone tell for sure if this truss has two or three bearing points?

enter image description here

John
  • 169
  • 2
  • 6
  • A slab is not a footing (though there could be one underneath). It's merely coincidence that the wall travels full-height. You can see the thickenened edge footing at the outer walls. – isherwood Feb 06 '19 at 20:29
  • @isherwood, but what about the first floor ceiling trusses ending on the wall? Doesn't that indicate that at least the 1st floor section of the wall is load bearing? – Jim Stewart Feb 07 '19 at 15:30
  • Good point. That's true at least where those trusses rest. It's common for footings to exist under a slab at specific places. – isherwood Feb 07 '19 at 16:10

4 Answers4

5

This is definitely a 3-bearing truss and it requires the support point in the middle. The reason I can see that is because a two point truss is going to have a lot of tension in the lower chord. The lower chord needs to be a continuous tie from one outer bearing point to the other outer bearing point to hold the walls from pushing outward. At the midpoint, you can see that the bottom chord of the right vaulted side connects to the midpoint of the center vertical member. There is not a bottom chord connected at this point tying to the left bearing point to counteract that pulling force. Therefore, that vertical member would be under a large bending force if there wasn't a vertical bearing point below it. With the center vertical bearing point, the right side and the left side effectively act as their own independent trusses each with their own bottom chord from the midpoint support out to their corresponding outer supports.

ThreePhaseEel
  • 79,142
  • 28
  • 127
  • 220
sam
  • 51
  • 1
  • 1
  • Hello, and welcome to Home Improvement. Thanks for the answer; keep 'em coming. And, you should probably [take our tour](//diy.stackexchange.com/tour) so you'll know how best to contribute here. – Daniel Griscom Feb 09 '20 at 03:17
4

It is unlikely that a residential truss has a load bearing center point unless it was carrying another truss load and being used as a girder. That doesn't appear to be the case. It appears that the truss was too low once it spanned the high ceiling area and the clearance was elevated to create a vaulted ceiling at the top of the stairwell. That truss appears to only have two load bearing points. Trusses are also marked at the load points when manufactured. I would still call the architect to verify.

Jerry_Contrary
  • 3,665
  • 8
  • 24
  • I agree, but this was probably a design choice and not a remedy to head clearance issues. There will be a label at the gusset point if it's load-bearing. – isherwood Feb 06 '19 at 20:26
  • 1
    The horizontal part of the shown truss is the basic ceiling height for the 2nd floor (8ft), and the vaulted part continues as a full vault beyond what's shown here (there are five of these studio trusses, then vault trusses to the end wall). Tough to describe but yeah, I'm pretty sure it's a design choice. – John Feb 06 '19 at 20:57
4

I’d be surprised if it isn’t a 3 point bearing truss and the center wall isn’t a bearing wall, because: 1) wall was designed as 3’ high but built full height, 2) wall was not shown as “bearing wall” but wall shown as 3’ high, 3) truss bearing on “Jack trusses” on left side of drawing, 4) vaulted truss does not have thrust brace connected to left side truss.

1) If a wall is changed during construction, it’s usually for a reason. Here, it appears it could be changed easily because the first floor wall and the second floor wall align.

2) Because the wall was NOT shown as a bearing wall (as you say) and the wall was originally shown as 3’ high, any change is due to on site conditions and specific construction procedures. That is to say, the truss manufacturer probably notified the architect and owner that they COULD build the truss as shown but at a greatly increased cost. Architect’s design ideas often are changed due to cost, etc. (value engineering).

3) The connection of the truss on the far left is highly unusual and gets extremely complicated with a 2 bearing condition. (Is it really constructed like that?)

4) If the trusses are really constructed as shown, the center wall becomes more important as a bearing wall, because it does not have a diagonal thrust brace at the bottom of the vaulted truss where it connects to the truss on the left.

A simple check (because you can’t see the footing) would be to see if the wall on the second floor continues (and the vaulted truss continues AND the wired connection on the far left continues.) If you can look in the attic, you will probably find that it’s 2 trusses.

Remember, many adjustments are made “in the field” during construction due to cost, ease of construction.

Lee Sam
  • 22,822
  • 3
  • 19
  • 42
  • Thanks for the answer. I've added a plan view showing the location of the wall and the 5 trusses of concern. (This may also clarify the weirdness with the jack trusses over the entry.) I've verified that the highlighted trusses were manufactured as shown in the elevation. Can you explain the comment about lacking a diagonal thrust brace? I'm not sure what that is. – John Feb 07 '19 at 04:23
  • The trusses I have seen which have only two load bearing points located at the two ends have a linear bottom cord. This cord is always in pure tension with no net bending forces at any gusset. The arrangement here suggests to me that the the wall is load bearing. – Jim Stewart Feb 07 '19 at 14:08
  • It appears the right side trusses for the 1st floor ceiling/2nd story floor end on the wall in question The 1st floor part of the wall in question is therefore load bearing. So the 2nd floor of the wall could also be load bearing. – Jim Stewart Feb 07 '19 at 15:20
  • I'm gonna go with "load bearing" on this, for the following reason: In the plan view, I've highlighted the 5 trusses that touch the wall in question. Just left of this are two trusses above an opening (no wall there). This area has the same ceiling profile (part flat, part vaulted), but the trusses are symmetric, vault trusses. It seems logical that the builder switched to vault trusses here because there is no wall to carry the load of the vertical member of the studio trusses. In other words, if the studio trusses don't need support, they probably would have used them in the opening as well. – John Feb 11 '19 at 21:33
0

From the elevation view, it looks like a 3 point bearing truss. But if you look at the plan view, it looks like the truss is a 2 point view, since the highlighted wall doesn't go the full length of the structure. This wall is only present under 5 trusses, this lead me to believe that the the wall isn't a bearing wall. Assumption: the trusses are similar throughout the length of the structures.

Driss
  • 1