Building a California Fire Wall with nice siding?

[Vintage Veloce]

So apparently if you build your garage within 5' of the property line, in the California building code section there is a table in section R302 that says you need a firewall as follows:

"1 hour-tested in accordance with ASTM E 119 or UL 263 with exposure from both sides"

I had hoped to make side entire building with redwood lap siding to match the house. Unfortunately, I haven't been able to find a way to do this.

Actually, the only fire wall assembly I have found that uses 2x4 studs and that meets the "both sides" requirement is this W408

Details here:
UL Design W408

This design lists a variety of siding (exterior cladding) options, but the only wood one is plywood or OSB. I'd end up using a cement siding like Hardieplank to implement this (See 6D in W408).
Additionally, this is a fairly complicated wall with 2 outside layers of type X gypsum and an external layer of heavy 2-sided LP Flameblock OSB.
And this LP Flameblock stuff doesn't seem to actually exist around San Diego.

Is there a better way to do this firewall? If not I guess I'mm make just that one wall with Hardieplank following W408.
Is there an easier way that I am missing? (And am I missing a way that lets me make the wall with regular redwood siding on the outside?)

C

 

[Norcal]

Can you special order the LP product, and why not Hardi? The wood sold today is not very good compared to what used to be available.

 

[Vintage Veloce]

edit, misunderstood Norcal's comment, fixed now
Norcal, I might be able to special order the LP Flameblock, just looking for an easier assembly if there is one.

On the Hardie vs Redwood, I'm not a big fan of Hardie for a lot of reasons, but I'd rather not start a debate about that!

C

 

[aircommuter]

We use stucco or scratch coat with veneer stone.

 

[theoldwizard1]

Check for exterior grade gypsum/plaster board. The problem is, it has nor shear strength so you would have to add wind bracing to the wall.

 

[aircommuter]

If you aren't too far from a lumber yard that is near a SFRA, that is where the code calls for a fire wall on the entire house. In the mountainous area. They may have it.

 

[Rock knocker]

I had a nice response all type up and lost it. The American Gypsum Association has a fire resistant design guide available. It is easy to google up. I think you want to start at WP 8105. One issue may be the location of the shear plywood in the assembly.

I personally would prefer an assembly that used Type X densglass and OSB on the exterior versus the LP product. I don't live in a wildfire zone but does http://www2.wwpa.org/Portals/9/docs/TN2008-01Rev10.pdf
indicate that redwood rabbeted bevel applied exterior to the fire rated assembly meet the flame spread requirements?

Whatever the final answer is regarding the redwood, the design guide will give you many options for your wood framed fire rated wall.

Hope this helps