Retrofit fireproof to safe

[Deleted member 174758]

It's not good practice to protect a steel beam with timber battens and board, if protecting a steel beam then steel angles should be used rather than timber battens. Or the fireboards can be screwed together around the beam.

Firstly the timbers used for this cladding are generally pressure treated in a fire retardant. Secondly, the steels themselves are coated with 3 layers of intumescent paint. Thirdly, the timbers are shot nailed to the steels. Fourth, with two layers of FR plasterboard and the joints fire mastic sealed it will take 2 hours or more for the temperature to rise sufficiently to cause charring of the timber. I have seen and installed this sort of fire cladding on a number of occasions in recent years - all the work was to architects drawings and was approved by the structural/fire engineers.

 

[Mottie]

You're all overthinking it. Search 'A4 fireproof document bag' and put your stuff inside that. Sorted!

 

[freddiemercurystwin]

Firstly the timbers used for this cladding are generally pressure treated in a fire retardant. Secondly, the steels themselves are coated with 3 layers of intumescent paint. Thirdly, the timbers are shot nailed to the steels. Fourth, with two layers of FR plasterboard and the joints fire mastic sealed it will take 2 hours or more for the temperature to rise sufficiently to cause charring of the timber. I have seen and installed this sort of fire cladding on a number of occasions in recent years - all the work was to architects drawings and was approved by the structural/fire engineers.

You've been doing it all wrong lol. Intumescent paint is never to be used without a 50mm clear void all around it, it just doesn't work otherwise. And why would you paint a steel with intumescent paint and then clad it - employing two different methods for fire protection? Your timbers will still get super hot and the expand/deform at a different rate to your steel structure, your screws or fixings will be as hot as the fire on the outside and will still char the timbers, reducing their effectiveness - your timber may be fire resistant it is not fireproof, structural engineers know diddly squat about fire protection, fire engineers know all about strategy but not the specific products used, approval for that will always have to be sought from the product manufacturers nowadays, (post Grenfell) nobody else.

 

[Deleted member 174758]

I'd suggest you direct you comments at the architects, structural engineers and fire engineers as well as the BCOs who oversee and sign off all this work - we are instructed to work from their drawings, generally GCs as opposed to specifics, which include all this detail. It's NOT a personal decision - it' a written instruction which is contractually binding.

Having dealt several times with burn-outs which used similar techniques of fire boarding, I personally have seen no sign of the timber battening deformation in the way you state (but then, hiw nany burned out buildings do you work on in a lifetime?). This is possibly because the fire brigade brought the blaze under control early enough. I have, however, seen metal clad framing and even structural steels which have buckled and failed, taking the PB with it, whereas timber joists in the same part of the structure have charred and survived

AFAIK in retail buildings it is standard procedure for the main contractor to intumescent coat visible structural steels before handing the structure over to the fit-out contractors - there may be a gap of many months or even years between completion and hand over to the next contractor (longest period in my own case was more than 10 years)

 

[big-all]

as an aside
if you experiment by making a sample box and try burning as a test please be aware some fairly evil fumes can be given off so be careful
also in a sealed box without ventilation the fumes from drying no nails or other can be quite an irritant

 

[freddiemercurystwin]

I'd suggest you direct you comments at the architects, structural engineers and fire engineers as well as the BCOs who oversee and sign off all this work

I work with all of those every day. I specify fire rated products all the time, I produce the drawings contractors need to follow and often they need to be signed off by the manufacturers, all of which is now test based not based on what was done in the past because someone thought it was OK.