Fire wall

[richard.selwyn]

Not sure if this is in the right section, but here goes.
I have a very good client who needs a 1 hour rated fire wall adding in the attic of his hotel to comply with local fire regs.  The attic is currently separated from the rest of the hotel by a single sheet of "sheetrock/plasterboard" screwed to metal studding.  Whilst I generally build built in furniture for him he absolutely wants ME to insulate his attic.  I don't want to do it and am not qualified, but even if someone else does the job I would like to make sure it is done right.  No one, from the firebrigade to the local authority to the other builders can agree on what constitutes a 1 hour fire wall.  The roof timbers are exposed.  The building is traditional ancient timber frame and brick.
I seem to think that 2 sheets of 12.5mm firerated sheetrock would work, but what do you guys think? How can one make a join between the wall and the exposed roof (laths and slate) ?
(I've just fitted over 2,000 euros worth of firedoors and doorclosrrs for him so would like to be helpful)

Help please!
Richard

 

[Alan m]

as far as i know thare is a formula for working this out . i seen it in a textbook once. it has got to do with the thickness of the sheetrock etc and other variables. doubling the layers of shhetrock will help the fire rating but how much i dont know for sure. look up engineering books .

as for the roof members. i presume yoi are building a stud wall as a party wall . i would bring it up as far as possible and return the sheetrock (of whatever thickness is needed  )back across the roof line for a couple of rafters to help slow the spread of the fire

 

[Holzhacker]

Ah, fire walls, the topic of many Code discussions. A couple of notes.
Yes, 2 layers of 5/8" firecode drywall is essentially considered a 1 hour firewall for practical purposes. Most municipal inspectors will let that pass and not think about it any further So on the one hand you would be safe doing that.
However, when it come to "fully compliant" fire walls, whether 1,2,3 whatever hour rating. There are specific rules and design criteria to follow. A 1 hour wall can be built several different ways. The design criteria covers everything from drywall thickness, layers, screw size, type, spacing, tape joints, expansion joints, you name it.
The easiest resource for you, the one I usually use for litigation work and refer clients/contractors to is the USG manuals. USG puts out many different manuals for various types of drywall construction. I'm guessing all are posted on their website somewhere, I have hardcopies of the ones I need so I can't give you a direct link. www.usg.com should get you started. Try looking for these manuals. One or a couple should be appropriate to your situation.
SA925 - Area Separation Wall systems; SA925 09250 - Area separation Fire wall/party wall systems; SA924 - drywall/wood framed systems
SA923 - Drywall/steel framed systems
Also the 'Gypsum Association' puts out a 'Fire resistance design manual' that I also use as a reference. You can try looking for it but you typically have to buy it.
PM or email me if you want and I can scan a few 1 hour pages and send them to you.
Hope that helps, Markus

 

[Brice Burrell]

Ha, remember this is a worldwide forum [big grin], Richard is from France so your reference isn't going to be much help.

 

[Holzhacker]

Brice, I thought about while writing the reply. Hopefully for him USG sells in France or there is an equivalent. Quite frankly, I'm surprised they care about fire wall separation codes. From what I've seen they don't seem to care about plumbing codes too much, or structural in vintage buildings.
As we like to say here, 'The Plumber protects the health of the nation'.

 

[richard.selwyn]

Thanks for the replies. Other countries' codes are interesting to me since the code here seems incomprehensible. Why go to all the trouble of insisting on  a one hour fire wall then allow a half hour door?
Anyway I'm am somewhat the wiser, but still don't really have an answer.  [unsure]
Regard,
Richard [embarassed]