Fire rating of brick veneer wall systems


(Robert Holland) #1

Just wondering if anyone has any fire rating info for brick veneer wall systems. I’ve managed to track down a document from ThinkBrick.co.nz which shows two way ratings for various constructions but there’s no information about testing or data sources… hoping to not have to just use a James Hardie JHETGJ system with brick veneer on top.


(Geoff Merryweather) #2

I assume the ThinkBrick document you have seen is the technical note TD3
midlandbrick.co.nz/wp-content/uploads/2015/05/Fire-Ratings.pdf.
If it is a new wall, you will need to follow the manufacturers’ instructions including minimum framing size and linings.
Brick walls in a typical modern house are neatly stacked vertical piles of rubble… The timber frame behind carries the roof load and the bricks are only a cladding or rain screen no different than a metal cladding. The bricks are tied back to the frame with wire brick ties hence the wooden frame does the real work and hence needs the universal wall Fyreline inside etc.

If it is a historical building with structural brick walls (e.g. interlinked 2 layers) then the
Brick Industry Association TN16b (Brick Industry tech notes) has some guidance on fire resistance (tested to ASTM E119 being US based). I think this came from some fire tests in a useful book put out by the US Department of Housing called the “The Guideline on Fire Ratings of Archaic Materials and Assemblies” which is a handy thing to have in the files if you do work on old buildings. I understand the cement type is important to the wall performance as well as if it is solid or hollow which affects the minimum equivalent thickness and if there is combustible framing in the cavity between 2 wythes.
Fire Ratings of Archaic Materials and Assemblies

Note the 50mm cavity in bricks needs to be looked at for fire separations such as IT walls. Monier have a detail for vertical junctions and there are propriety products for horizontal joins, depending if you a have a shelf angle and drain flashing at the floor level or a continuous cavity.
The other one to watch is that if there is a heat release rate limit, then the barrier at the rear of the cavity would presumably have to comply with the HRR limit in the same manner as other ventilated cavity wall systems. Many brick walls just use building paper, not a fibre cement board RAB, which would not comply with the cone test limits.
G


(Robert Holland) #3

Thanks Geoff for your very thorough guidance. Yes, that was the document I was referring to and following discussions I’ve had recently with people within the brick industry, I wouldn’t rely on that document as it is based on pre-1993 testing done by Monier, and you can’t get hold of any test reports etc… Apparently there is some ongoing discussions between the brick suppliers and BRANZ regarding fire rating of 2 storey veneer system. Understood that one could rely on the internal GIB for the interior to exterior rating, but I was hoping to rely on the brick for the other direction. It is now apparent I will have to use another layer (e.g. RAB) on the outside of the framing to achieve my 2 way rating. Thank you also for the documents for historic buildings, much appreciated.


(Robert Peart) #4

You may get some guidance on brick wall fire ratings from http://thinkbrick.blob.core.windows.net/media/1402/manual-05-design-of-clay-masonry-walls-for-fire-resistance.pdf . This publication deals with brick walls that are not of the brick veneer type. Note however the constraint arrangements.


(Robert Peart) #5

Oops that didn’t work. Try Design of Clay Masonry Walls for Fire Resistance


(Paul Clements) #6

Hi Rob
Monier in June 1998 produced design note A4 which covers varying combinations of Gib, clay bricks, wall loadings and FHC 1 and 2. Rating varies from 24 minutes to 60 minutes. No mention of testing organisation or test standards.
Paul C


(Geoff Merryweather) #7

Having a dig in the archives, Western Clay Products published a guide which is attached (I hope). It has some info on anchored brick veneer.
Check the details, as for most brick construction it looks like 1hr is it.
While it might provide some guidance for an ANARP solution, I would hesitate to rely on it for new work due to not being a (NZ) tested system and the difference between various bricks and construction appears to make a large difference.


(Robert Holland) #8

Thanks Robert, yes, saw that one.


(Robert Holland) #9

Thanks Geoff, a very useful document for ANARP’ing existing buildings but yes, unfortunately nothing out there for brick veneer systems at all! Something to add to BRANZ’s to do list.