Thread: NBCC fire wall narrative

Mortarless CMU firewall for townhomes.

Seen them 3 times in 5 years.
Need NBCC code or Canadian narrative.
I have the 2015 NBCC code and will try to look it up as well.
Much thanks.
mortarless cmu.jpg

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The NBCC, and Canadian narrative of it, will likely only state what is required - i.e., a 2 hour rated wall from foundation to roof deck and or 18 inches above roof deck and or options.

Neither of which will likely address a dry stacked masonry wall.

What you need is for the builder to provide the design standard to which such a dry stacked masonry wall meets.

Down here in the states, the requirement for a CMU wall used for a firewall, fire partition, fire barrier, etc., needs to meet a design standard, and one of the things that design standard requires each concrete masonry unit to bear the UL Classification Marking - here is an example of a UL Design for CMU: http://www.westbrookblock.com/wp-con...11/10/u905.pdf (see that asterisk at the end of "Concrete Blocks*"? Look down at the bottom of the page and you will see "*Bearing the UL Classification Marking")

That marking is because regular concrete masonry units have face shells a minimum 1-1/4 inch thick, CMUs for rated walls, 1 hr, 2 hr, 3 hr, 4 hr, have face shells which are progressively thicker - the cell holes get smaller and smaller as there is more and more concrete in each block, once laid, the only way to tell is the marking on the block.

You would need a design approved for Canada which specifies the block, the marking, and the mortar (or lack thereof).

The code would only tell you that you need a 1 hr, 2, hr, 3 hr, or 4 hr wall ... the design tells you what meets which rating.

I doubt that a dry stacked CMU wall meets any requirements - CMU do not precise fit together, without mortar, what is going to seal the bed and head joints to keep hot gases and flame back, and what is going to keep the blocks stacked together so they do not come tumbling down?

Add to the above that those are stack bond, not running bond - there is little strength in that wall unless it has a lot of reinforcing steel in it and is poured solid (which would address the bed and head joints not being mortared.

Just some food for thought.

I thought there might be fire ratings for masonry firewalls. I know about the mortar bond. It's the mortarless and underwriters laboratories that's the caveat. Put many hours behind those blocks.

UL certifies exterior walls, doors and windows for fire-resistance ratings, exterior wall coverings, metal composite materials and external insulation and finish systems (EIFS).

I will get back when I review the NBCC fire code.

In Ontario in Volume 2 of the OBC - "Fire and Sound Resistance of Building Assemblies" (Supplementary Standard SB#3) provides listed "assemblies". I'm sure you will find something similar the NBC, since OBC is largely based on the base requirements of the NBC.

Regarding concrete block normal weight fire separations - with hollow core concrete block (Wall number B1) 140 mm and 190 mm concrete block (B1a - 140 mm bare concrete block provides a 1 hour FRR for both load bearing and non-load bearing walls). (190 mm block provides 1.5 hour FRR for both load bearing and non-load bearing walls).

There's no mention about coursing or mortar requirements.

Originally Posted by Claude Lawrenson

In Ontario in Volume 2 of the OBC - "Fire and Sound Resistance of Building Assemblies" (Supplementary Standard SB#3) provides listed "assemblies". I'm sure you will find something similar the NBC, since OBC is largely based on the base requirements of the NBC.

Regarding concrete block normal weight fire separations - with hollow core concrete block (Wall number B1) 140 mm and 190 mm concrete block (B1a - 140 mm bare concrete block provides a 1 hour FRR for both load bearing and non-load bearing walls). (190 mm block provides 1.5 hour FRR for both load bearing and non-load bearing walls).

There's no mention about coursing or mortar requirements.

Thanks, Claude.
Ever see mortarless CMU in firewalls?

I am awaiting Quebec's amended code this year.
I have downloaded Secure PDF files as mention. Likely going to order a paper hard cover volume. Hard to negotiate the codes on online PDF NRCC guidelines.
Question to anyone. Any tips would be greatfull if you use the online Secure PDF files.
Learn curve like anything else I guess.

There is a mortarless and stackable concrete block made in Ontario. It has been around for quite some time. However regarding your photo, it would be difficult to tell unless you know from the original build.

Structurally it may be questioned unless theres some further investigation on how the blocks are adhered. There also may be concrete or mortar fill with or possibly without rebar.

From a visual home inspection perspective your narratives are primarily limited, to what you can see. Further evaluation required.

Originally Posted by Claude Lawrenson

There is a mortarless and stackable concrete block made in Ontario. It has been around for quite some time. However regarding your photo, it would be difficult to tell unless you know from the original build.

Structurally it may be questioned unless theres some further investigation on how the blocks are adhered. There also may be concrete or mortar fill with or possibly without rebar.

From a visual home inspection perspective your narratives are primarily limited, to what you can see. Further evaluation required.

Exactly. Further evaluation by a licensed professional.

NBC 2005 and 2010 Firewall and Fire Separation Requirements

The purpose of this bulletin is to review National Building Code (NBC) of Canada 2005 and 2010 requirements for firewalls and fire separations in relation to the Advantage ICF System®.

Monolithic Concrete Wall Thickness Fire-Resistance Rating
Minimum 150-mm thick Type N concrete 3 Hour
Minimum 171-mm thick Type N concrete 4 Hour

The following NBC definitions will help to understand these differences:
1. Fire separation means a construction assembly that acts as a barrier against the spread of
fire and smoke. NOTE: The fire-resistance rating of a fire separation may be waived in
some cases on the basis of the presence of an automatic sprinkler system.
2. Firewall means a type of fire separation of noncombustible construction, which
subdivides a building or separates adjoining buildings intended to resist the spread of fire. A
firewall has a fire-resistance rating as prescribed in the Code and has structural stability
to remain intact under fire conditions for the required fire-rated time.
3. Noncombustible construction means that type of construction in which a degree of fire
safety is attained by the use of noncombustible materials for structural members and other
building assemblies. Except for closures, the NBC states that required fire-resistance
rating for a firewall shall be provided by masonry or concrete.