Load Bearing Wall?

[Jonmanning123]

Can someone help me put my mind to rest...?

I am looking to take out a wall. My roof has trusses at 24" OC or so. Each truss, however, has a gusset plate at the CL in the bottom chord. Is this normal? See the attached picture. By the geometry, I cannot figure out how this wall could be load bearing but it has two horizontal 2x4s at the top which makes me a bit concerned. Is this normal for a partition wall?

Thanks for any help!

 

[SLTA]

Likely not load bearing. Some folks put double plates no matter the wall. How old is the house?

Hate to say it, but best to confirm by hiring a local structural used to residential investigation to check it out. If you're really worried, header off the opening you want with posts and footings down to the foundation.

Good luck!

Please remember: we're not all guys!

 

[txeng91]

Like SLTA said the wall should not be load bearing; a vertical in the truss at the bearing location would indicate that it is. That being said the wall could be providing additional support if the truss can not span on its own, but 23' is not very far for a roof truss. Not sure what the web/chord connections look like but if they are just nailed together, the truss probably wasn't engineered and the connections could be undersized. If they are all metal plated, they likely were engineered to span the 23'. You can get a structural firm to analyze it and see if the truss is rated for the span. Or like SLTA said you can frame a header over the opening, assuming its not a very long span, without affecting the current performance of the system.

 

[msquared48]

Truss is not configured to have a support point at the wall. The wall should not be in contact with the bottom chord. There should be a 1/4 to 1/2 inch gap between the wall top plate and the truss bottom chord. Way too common a mistake with framers.

Mike McCann, PE, SE (WA)

 

[dik]

Double top plates are used to tie walls to each other, either at corners or at intersections... one plate is secured to the wall at right angles. Conventional wood construction. There is often a gap at the crossing wall to permit deflection.

Dik

 

[BAretired]

It shouldn't be load bearing, but it could be helping the trusses in carrying load, so it pays to be conservative. Make sure the trusses are capable of carrying the load over the 23' span. I would be particularly suspicious of the bottom chord splice at midspan.

BA

 

[MotorCity]

I agree that the truss was most likely not designed to be load bearing on the wall. However, I would bet that over time it has become load bearing since the framers do not usually provide a gap between trusses and non load bearing walls. As such, if the wall has become load bearing and you remove it, you will most likely see an increase in deflection of the bottom chord. This could cause cracking in gyp board ceilings or any other finishes attached to the bottom chord.

 

[msquared48]

True, it could. And to any framing below the wall too.

However, if this is a residential truss, I would not expect the truss deflection to be more than 1/4" or so under full load.

Mike McCann, PE, SE (WA)

 

[Nor Cal SE]

Jonmanning123, based on your sketch I'm presuming there is no 2x/other blocking immediately above the double-top plates in question that runs between truss bottom chords, is that correct? The absence of blocking would further legitimize the earlier statements from others that this wall is not load bearing.

 

[concretemasonry]

The joint in the bottom chord is quite common since 23' long lumber is very rare.

I would worry about the center joint if it was a site built truss since it takes some engineering to make a wood "gusset" plate work and be reliable. I doubt the person/contractor was able to even get metal plates and used some plywood for the truss connection since truss manufacturers will not sell metal truss plates to contractors because of liability.

When I was involved (partial owner) in a truss plant some years it was automatic to have the center truss plates on both sides of the truss. Obviously, the truss engineers from the plate supplier we used often designed the truss with critical plates on both sides for strength and handling purposes.

I appears the contractor on the site framed the walls with double 2x4s at the top of the interior wall because it was intended for the wall to be carry a significant load due to the truss deflection.

Dick

Engineer and international traveler interested in construction techniques, problems and proper design.

 

[JStructsteel]

As engineers, would you "say ok" based on engineering judgement, or measure up the truss and do an analysis?

 

[XR250]

As engineers, would you "say ok" based on engineering judgement, or measure up the truss and do an analysis?

If you do the analysis, how are you going to know if the plates are adequate? Their capacity if proprietary AFAIK even though I have heard 80 PSI tossed around. Furthermore, you then have to pull up the insulation at each truss and each plate and determine if they were installed properly with the proper number of teeth on each member. You would never stay in business doing it properly.

I typically just look at the truss and see if the chord, web sizes and spacing seem consistent with other trusses I have reviewed and make a decision based on that.

 

[Jonmanning123]

Thanks for the responses everybody!

I'm a tunnel structural engineer by trade so I'm almost a bit embarrassed that I couldn't figure this one out right away. Everything online says - "when in doubt consult a PE." But what if you are one? No one can know it all, I guess...

I went up into the attic and there is no blocking immediately at the wall. All the center plates appear to be in good shape. I also ran some analysis too just for fun. I took the wall out this weekend and there was no noticeable sag. Thanks for the help!

 

[XR250]

I appears the contractor on the site framed the walls with double 2x4s at the top of the interior wall because it was intended for the wall to be carry a significant load due to the truss deflection.

Balderdash! 99% of interior walls are typically framed with double 2x4 top plates

 

[hokie66]

Perhaps too late since you have already removed the wall, but non-bearing walls can sometimes be bracing walls for lateral forces.

 

[txeng91]

Perhaps too late since you have already removed the wall, but non-bearing walls can sometimes be bracing walls for lateral forces.

.

There are certain circumstances where that could be true, but with this configuration there's not much of any kind of load path for this wall to provide significant lateral bracing. That being said, I see people specify lateral bracing in configurations like this all the time while blindly going off the code wall bracing tables.

 

[msquared48]

Unfortunately very true.

Mike McCann, PE, SE (WA)

 

[hokie66]

dnlv,
You may be assuming a diaphragm at the roof level. But in many countries, the effective diaphragm in houses is at the ceiling level, so the internal wall would be on a direct load path.

 

[XR250]

I agree with hokie66 - specially when you have a gable roof. 1/2 the wind load goes into the ceiling diaphragm unless the endwall is balloon framed or some complicated kicker mechanism was installed in the attic.