huangyhg

fireprroofing timber structures
we have an old mill (timber)structure and the owner would like to use the second floor for misc. metals fabrication shop. to fireproof and protect the wooden floor and the beams below they are thinking of placing a light weight concrete slab over the hardwood floors. does this present a fire hazard problem? is there another way to firepproof the hardwood floor and timber beams below?
any information would be greatly appreciated

i dont think you can "fireproof", it will just make the fire spread slower from main to upper floor (or other way). i would be more worried about the load because the second floor might not be strong enough for a machine shop plus the lightweight concrete you are adding.
we can check the strength. it should not be a problem since this was a manufacturing facility. the first level has slab on grade and it has been operatiing as a fab shop for many years. the main concern is about metal grinding and welding on the second level.

you would only have to fire proof if the building code requires you to. ie height and area limitations and the fire resistive requirements for structural elements sections.
i can see where the client maybe worried about welding slag getting in the wood timber joints. most likely you don't need to fireproof the structure per code requirements.
the problem with adding concrete is that the subsequent mass becomes a seismic consideration. by adding this mass to the structure, the code requires that the structure be able to resist the resultant seismic force. most timber mill buildings were not designed for seismic at all.
look for something lighter that will not burn. maybe checkered plate in localized welding areas? gypcrete may also be an option.
are the beams and flooring above being hit by metal embers or slag? if so a layer of fire coded gyp board will help.
good luck, let us knonw what you decide.
i am sure your local fire marshall and insurance company will have plenty of advice -- most of it you probably won't like.....
sprinklers may help
good luck
boric acid dissolved in water can be sprayed on wood for fire retardant and termite control. there are companies that provide this service.
i saw a new product demonstration - real heavy sales pitch which turned me off - called no-burn that appears to be something you may want to look into.

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