One hour wall termination

[Robert]

Hello. I need a 1 hour wall because I am less than 5' from property line (CA requires protection on both sides of the wall). The Roof/Clg. assembly is exposed beams with a wood plank ceiling and concealed rafters/insulation above (spray foam insulation...no airspace).At the interior condition: Can the 5/8" type "x" gyp. bd. terminate at the wood plank ceiling (rather than all the way up to the roof sheathing) if we add a second fireblock between the rafters above? I believe that a certain thickness of wood can provide the equivalent fire protection that the gyp. bd. can but am not sure how thick, and if it would even be considered 1 hour. Please see the crude sketch. Thank you.

View attachment 2185

rake.PDF

rake.PDF

 

[north star]

& : : &

Recommend that you discuss this proposed installation

with the AHJ FCO and or BO, ...to get their input first.

& : : &

 

[Robert]

The inspector suggested adding the additional wood fireblock, though I don't know what thickness will satisfy 1 hour.

 

[Builder Bob]

Check with NDS calculated fire resistance. The proposal will still have to be approved by the AHJ

 

[Robert]

Thanks will do.

Does the size requirement in Type 4 Heavy Timber construction have anything to do with fire resistance?I believe it does and was going to use that as a guide if I couldn't find any listed assemblies for this condition.

 

[Builder Bob]

Type IV does not have any concealed spaces.... besides this is in the residential code and not the commercial codes. not sure if AHJ will let you mix and match code books.

 

[Robert]

Thanks....looks like the NDS has the char rate and depth of sawn lumber that I can apply for a 1 hour rating.