Masonry Bearing on Wood Bearing On Steel 3

[RFreund]

I have a situation where open web wood floor truss bear on a steel beam. The architect is showing wood blocking between these floor trusses with masonry bearing on the wood blocking. What are your thoughts on this detail?
Should masonry bear on wood that is bearing on steel?

Thanks in advance.

EIT

http://www.HowToEngineer.com

 

[msquared48]

I would bear the masonry on the steel directly, then find a way to support the joists, either off the steel, or the masonry, depending if the masonry is structural or not.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[woodman88]

Well I do not like the idea but it depends on the code and what the masonry is doing.
The 2003 IBC Section 2304.12 states that wood shall not support any dead load from masonry or concrete. But then gives four exceptions that can be done.
The 2009 IBC Section 2304.12 states that wood may support masonry or concrete if long term loading and deflection requirements are met.

Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.

 

[msquared48]

I am aware of the code allowances. Regardless, I would never do it.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[dhengr]

Rfreund:
The reasons for not doing this, or the problems it can cause have not gone away as Mike implies, and I would try not to do it. But, the codes have become slightly more liberal about this detail if all the exceptions are met, and the inherent problems are considered, as Woodman suggests. Putting a few courses of decorative brick atop a good stiff wood structure is one thing; while putting a masonry bearing wall or a heavy non bearing wall on a flexible wood system is quite another. The Arch’s blocking should be well fitted and standing like studs, not on its side like a rim jst. or sill plate, because the latter will still crush and settle over time. Provide adequate bearing, compression perpendicular to the grain at all wood support points. Make the lower course of the wall a bond beam with some rebar in it, and use joint reinforcing in the lower courses, to make the wall act like a deep beam, thus preventing cracking, and spanning over any soft spots.

 

[woodman88]

Well as I stated I do not like the idea of supporting masonry or concrete on wood. But have seen and approved it being properly done (being it was supported on a 8x beam, not the framing in the OP) in custom homes and country clubs.
As per the OP detail, I do not see any way I would be willing to made it work (but I may approve of a detail that did work) and like msquared48 would place the masonry on the steel beam.

Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.

 

[MiketheEngineer]

Well ---- as stated the codes now allow it and from what I read it is not really load bearing - other than just transferring loads vertically.

Not my favorite detail - but you can make it work. Might want to use "treated" lumber.

 

[msquared48]

I just do not like it as wood rots with the intermittent presence of water, eventually, even if it is treated. Just takes a little longer.

So, bearing over wood, eventually you will see cracking in the masonry. Pay me now or pay me later...

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[RFreund]

Thanks guys I appreciate the comments. DHEng - good insight and detail, thank you.

It appears that this detail would only be used to support brick veneer approx 10' tall. So it is non-bearing however I'm still not sure that this is a good detail. I feel like 'soft-spots' could still be an issue and lead to cracking. I will think about an alternate detail.

EIT

http://www.HowToEngineer.com

 

[dhengr]

RFreund:
I can’t see your detail from here, but that 10' high brick veneer would make me nervous too, primarily cracking with so many joints. Be sure your blocking is uniform and consistent to minimize soft spots or much flexing btwn. hard spots. Put a vert. stud type block along side each wood truss too, just for consistency, and then a couple btwn. each truss. At least you want uniform settlement. Maybe lag screw a 6x3.5 angle to the studs, and resting on the sill plate, or whatever, a shelf angle, acting as a tension member and spanning member. Don’t forget wind and water plane system, clean out of cavity, flashing and flashing drip edge, weeps, etc., all on top of the angle. Caulk the angle in btwn. the wood and the underside of the flashing. Make them install the brick ties as they lay the wall up, and plenty of them. Also, remember wood and concrete tend to shrink, while brick tends to grow in height.

 

[woodman88]

You might want to consider a 3.5"x5"+- pocket at the top of the floor truss for a 4x6 beam to sit in and support the masonry. It is easy to do with an open web wood floor truss.

Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.

 

[McLJ]

I have done it for veneer only, and in only very limited cases; otherwise it's a really bad idea in my book. Strength, or over-strength issues aside, wood shrinks. As the wood shrinks it can cause 'settlement' in the masonry.

If the masonry is exposed to weather, treated wood is required.

Another interesting note - brick exposed to weather 'grows'. Combining wood shrinkage with brick expansion can lead to ugly cracks if not carefully detailed.

LJ

 

[shobroco]

Contrary to all of our training and instincts, thousands of buildings were constructrd in the 18th, 19th, & early 20th centuries with wood nailers, lintels, beams, etc. laid right in the walls, and many are still performing as intended. HOWEVER, they were done with lime mortar, which is soft and self-healing for movement, and they mostly fail any sort of rational analysis or inspection. I have very infrequently agreed to masonry support on wood, but only if detailed correctly for shrinkage of the wood, the most likely source of trouble, and only if the load is relatively insignificant. A 10' high wall sounds like trouble in a few years, regardless of your details.

 

[RFreund]

Thanks again guys for your input. Sorry for no sketch, bad form on my part and now that I have time I have no scanner. However I believe we will bear the veneer on the steel.

EIT

http://www.HowToEngineer.com