Interior wall load bearing with floor trusses? 1

[tenn1440]

I just had a structural engineer come out to verify that a pair of perpendicular interior walls were or were not load bearing before taking them down but I wanted to get a second opinion.

I had been told by our home inspector, who is also a structure engineer, that generally with floor trusses most of your interior walls are not load bearing but referred me to his company for an evaluation to confirm.

The engineer came out and immediately said that because the trusses had a double vertical 2x4 right over top of an interior perpendicular wall that the wall was load bearing. There was also a single 2x10 (roughly 3ft long to cover the width of the hallway) attached to the three trusses that go over our hallway, where there isn't a perpendicular wall, that he thought was acting as a header. It also has two 2x4 skirts attached to the bottom of the 2x10 on both edges that look like they're in place to attach the ceiling drywall which makes more sense to me than using a single 2x10 as a header.

After he left I removed more of the drywall in the stairwell to get a better view of the trusses and it looks like the truss is floating above the perpendicular wall that he believes is load bearing. In one of the attached photos you can see the top plate of that wall with a gap under it and the ceiling drywall on both sides. Could this still be a load bearing wall even though I can't see anywhere that the wall is actually touching the trusses? I don't know how any weight could be bearing on that wall with the air gap there but maybe the builders just improperly built the wall and didn't do it to the spec that the trusses were engineered with.

Here are some general specs.

Truss span(running front to back of house): 26ft
Truss spacing: 16" o.c.
Truss depth: 20"

Span from front of house to wall in question: 11'8"
Span from back of house to wall in question: 15'6"

 

[tenn1440]

regular upload won't work so attached is the very rough floorplan sketch

 

[tenn1440]

and the weird 2x10 photo

 

[phamENG]

Is there a wall in the same place above? The doubled web members could be web reinforcement to support a point load from above rather than a reaction below. A 26' span for a 20" joist is certainly reasonable.

I think your intuition is good, but I wouldn't say your engineer is wrong without seeing it in person myself and, probably, analyzing the truss. One thing to remember - you're going to get what you paid for. If you just paid a few hundred bucks for a quick inspection and decision, you're likely going to get a conservative answer. So if there was any question about it, they're more likely to fail safe (this is a good thing). To do a detailed analysis the engineer will likely need a lot more information. Getting full measurements of the house and all of the truss chord and web members requires 1) full access to the entire truss and 2) a lot more time to sit down and run the analysis. Cost of that will vary based on your location and the engineer you choose.

 

[tenn1440]

@phamENG, thanks for the reply. Yes, there is a wall directly above that double web member. I took down some more drywall to make it easier for him to see and he said he's going to come back out tomorrow and take another look now that he can actually see what is going on behind the drywall. With the additional drywall removed I can see the full top plate.

At first I figured it was in fact load bearing because of a double top plate but once I climbed up I was able to see that there is a 1/8-1/4" gap between the top plate of the wall and the bottom of all trusses. If this wall was intended to be load bearing the framers must have missed that part unless I completely don't understand how a load bearing wall is meant to work.

The house is using roof trusses so the SE said that the trusses are only carrying the floor load and that none of the second story walls are load bearing so I guess that double web member would only be there to support the added weight of the wall itself. Could that also be why there is that random 2x10 there?

Attached is a photo of the better vantage point of the bottom of the truss and top plate of the wall in question.

 

[phamENG]

Yeah - probably not load bearing. Unless you have some super advanced magnetic anti-contact bearing points on the trusses. I'm pretty sure those don't exist, though, so we'll stick with probably not load bearing.

The 2x10 is a little bit of a mystery. Without seeing where it starts, where it ends, and to what and how it attaches I really can't say. Might be a clever way of trying to balance deflections - that sort of a point in a trussed floor can be problematic with deflections ripping floors apart at the corner.

With the drywall off and better visibility, your engineer should have a better view and should be able to figure it out. Good luck.

 

[dauwerda]

Many jurisdictions require stamped truss plans to be submitted with the building permit (even when the overall project does not need to be engineered). You may be able to contact your local building department and see if they have the truss drawings on file. If they do, you will be able to see whether the wall was designed as load bearing or not.

 

[msquared48]

My gut feel is that the wall is not currently load bearing. The gap is the main reason here although the trusses do appear to be designed to bear on the wall. Presently, the double studs should see no load.

My next questions are: (1) were the correct trusses provided, and (2) were the trusses supposed to bear on the wall.

As mentioned above, a quick check with the building department could answer a couple of questions.

Mike McCann, PE, SE (WA, HI)

 

[tenn1440]

Just to close the loop on this. The SE and the owner of the company who has been doing this for 40 years both came back out to revaluate after I pulled down more of the drywall. The owner was immediately able to confirm that the wall was not load bearing.

The double web member was in place to support the load of the wall above the truss. Each area where the double vertical 2x4 web member was in a truss also had a double top plate (if that is what it is called on a truss). Above each double vertical 2x4 was an extra 2-3ft piece above it to help absorb the point load of the wall above just like @phamENG suggested.

Thanks everyone for your input!

 

[phamENG]

Top and bottom of a truss are called chords.

You're most welcome - glad it worked out.