Brick veneer horz. deflection 2

[WWTEng]

What limits do engineers apply to deflection of steel stud backed veneer? H/600 seems too stringent.

 

[haynewp]

H/600 is very stringent but that is common now. It is recommended by the BIA I believe and required by the UFC if you are doing government work. I used to use H/360.

 

[Ron]

WWT...do a few wall failure investigations...not for collapse but for water intrusion...you'll see why the more stringent requirements make sense.

 

[concretemasonry]

Ron is spot on.

Especially when the moisture resistant barrier is not 100% and the studs corrode where the screws pierced the galvanized studs. - Total rebuild possible in the future.

There is a problem when the veneer is more rigid than the back-up.

Dick

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

 

[WillisV]

@Ron - it has been found through tests that there is no difference in water intrusion between L/360 all the way up to L/720. See

http://www.structuremag.org/Archives/2008-5/C-CodesandStand-Sprague-May08.pdf

I use L/600 per BIA generally, but in reality L/360 is just fine.

 

[WWTEng]

Thanks all.

Ron, ConcMas: Should it be more stringent of H/600 & 0.3"? I mean H/600 for 20' is 0.4", is that acceptable or should 0.3" be the limit.

 

[hokie66]

The link Willis posted is interesting, and I agree with its conclusions. Brick veneer will always be stiffer than a stud backup, so the emphasis should be on protecting the studs and using corrosion resistant ties, preferably stainless steel.

 

[abusementpark]

The building code only requires L/240 for brittle finishes.

I thought the L/600 criteria from BIA was for in-plane deflection (e.g. a lintel beam).

 

[DST148]

@WWTEng - See recent thread507-324646. Reading through this thread, it seems ACI 530-08 has done away with 0.3" deflection criterion.

 

[WillisV]

Be carefule here, you guys are mixing two different criteria. The masonry code, ACI 530, provides deflection limits for horizontal (supporting beam) type deflections. It used to be L/600 or 0.3", and it is now just L/600. The criteria for maximum deflection of facade type veneer for designing the backup as discussed in this post is given in BIA tek note 28b (which I again disagree with per my post above but use because it is the current standard of care) which can be found here

http://www.gobrick.com/portals/25/docs/technical notes/tn28b.pdf