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Discussion Starter · #1 ·
Hello, I am framing in part of a steel building and was looking for some recommendations on how to frame in the ceiling. The room is 18x24. My first thought was to use 18 foot 2x8s across the entire 24 feet and then add some blocking. Will that be enough support? Thanks
 

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retired framer
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18 ft is to far for even 2x10s. I think you want to look at TGI joists and that might allow some storage above if there is room.
 

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Discussion Starter · #3 ·
Thanks. I assume those joists can span the 18 feet without blocking? How tall would you recommend? Locally I can get 9.5, 11.875 and 14 inches
 

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retired framer
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Thanks. I assume those joists can span the 18 feet without blocking? How tall would you recommend? Locally I can get 9.5, 11.875 and 14 inches
The people that sell it can help you with the right size and the on center layout and plywood above if you want the floor above.. :wink2:
 

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If it is just a celing, you could probably live with the 2x8, although 2x10 would be better. If you plan on storing stuff up there, or having people walk on it, I would go with the TJI.
 

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https://www.awc.org/codes-standards/calculators-software/spancalc


Douglas fir south grade #2, 16" joist spacing, 20 psf live and 10 dead, L240 deflection. Looks like 2x10 works. Lumber yards will have availability, prices, etc. Must check for llat, warp and crown. Those sizes in the forum usually are garages or a workshop. As such, many of them don't have ceilings. Just rafters with ties. Before the roof, search how to insulate.
 

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Discussion Starter · #7 ·
Thanks.. it will be just for very light storage since I'll only have about 2 feet until the steel framing starts. If I made a beam of 2*12s could I run 12 foot 2*8s off that ? Might just be easier to get I joists, but much more money!
 

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Always best to check span tables. For a rough estimate, figure max span in feet is 1.5 times the height of the joist in inches. So a 2x8 max span is 12'. To span 18', you'd need 2x12. An 18' 2x12 is a chunk of wood! Probably better to use a beam and 2x8s.

Maybe trusses would work? That's out of my area of expertise. But it may be worth a call to your local truss mfgr.
 

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Beam may work but you must have the right size beam. There is no guessing for that. Beam also needs extra footings so the cost may add up. I joists are more sure materials but definitely higher cost. It is worth asking though for even 24" spacing and comparing with having to use 5/8 drywall and such. If for storage, why ceiling? No matter what you do, ceiling alone doesn't keep out weather and such. Also, as a storage, do you need clear span room? Use some posts in the middle?


My garage is about 21x21 and it has one post about midway. Double 2x10 beams and 2x10 ceiling joists for flat roof. I can put another floor on this.
 

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Discussion Starter · #11 ·
it seems like the 18 foot beam with 12 foot 2x6s would be the cheapest option. how many 2x12s thick would the beam need to be? This 18x24 room will be fully contained in a 24x30 steel building, so weather wont be an issue. Insulation on the ceiling and then a few sheets of plywood to store lightweight items on the top of the room.
 

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retired framer
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it seems like the 18 foot beam with 12 foot 2x6s would be the cheapest option. how many 2x12s thick would the beam need to be? This 18x24 room will be fully contained in a 24x30 steel building, so weather wont be an issue. Insulation on the ceiling and then a few sheets of plywood to store lightweight items on the top of the room.
We use 2x12s for a 16 ft garage door header and the least they get is 3 so I would say 3.
 
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