Well.... The building inspector here in town shot down my plans. I need to have a fire block every 10' both horizontally and vertically. Never mind that cellulose is more fire retardant than wood. So now I'm wondering if I should just scrap the entire Larsen truss idea and go with a regular tip up double stud wall. The only issue there is insulating the band joists. How are people doing this with double stud walls?
Also the inspector told me that 5/8" drywall was an acceptable fire break. I just can't imagine cutting little pieces of drywall to fit in the cavities in between the studs but maybe this is the best thing to do from an insulation point of view.

Does anyone have any ideas?

Posted By S-F on 22 Mar 2011 09:57 AM
Does anyone have any ideas?

Yes, ask himto cite the section of the code he is getting that from?  is he refering to draft stopping ?

I don't want to agitate this man as he has the power to make my life quite difficult so I have to be careful. By draft stopping I assume you mean keeping the balloon frame from becoming a chimney? All he said was that the code demands a fire block every 10' both horizontally and vertically.

Posted By S-F on 22 Mar 2011 10:45 AM
I don't want to agitate this man as he has the power to make my life quite difficult so I have to be careful. By draft stopping I assume you mean keeping the balloon frame from becoming a chimney? All he said was that the code demands a fire block every 10' both horizontally and vertically.

Plan reviewers and inspectors often overstep their authority, Everyone has a boss including the pope. I have often gone over heads if I am being asked to do something that is not legally required........ It is not an unfair question, so if you won't ask, it does no matter what any one on the forum thinks, just open your wallet and do anything he asks you to do.

Well I just talked to him and he read the passage from the code relating to this. It states that blown insulation isn't a fire block unless the manufacturer has proof of testing which demonstrates that it ie effective. I have been in touch with the cellulose manufacturer and they are sending some paperwork to me to show the inspector. Well see how that all goes. If he still won't agree I'm going to have to go with the regular double stud wall and wrap the whole thing in 2" of XPS.

Fire blocking is normally required by code. We stud to ceiling height and then We substitute a sheet of 5/8" drywall with a piece of 1/2" OSB a top it to bridge between the walls. If you line up the studs top and bottom this is adequate. Brian

Had I known it would be relevant I would have remembered what it was as he told me but, alas, I forget. As it turns out the code doesn't demand 10' in both directions but 10' horizontally and between each floor.

Draft stopping is common at ceiling drop/stud wall intersections , I have never heard of the horizontal stop

Well, I got some information from the cellulose manufacturer which I'm going to forward to the inspector today. Hopefully he'll buy it. If not, does anyone have any recommendations for me? Should I just build a double stud wall, try to web off each joist bay to dense pack them and then wrap the whole house in 2" XPS? Seems like a lot more work.

I think I have it figured out. I'll just extend the sub floor out to the sheathing. Can't believe I didn't think of this before. It's hardly any more work and should satisfy the inspector. Now the only question left is if they are going to demand metal bracing in the structural wall even though the outside is sheathed.

S-F;

if your sheathing is foam then you will need either metal strap, metal "T" or 1x4 "let-in" wood bracing

I'm using OSB not foam. The foam was an idea to deal with thermal bridging if I had to scrap the Larsen truss.