Floor joist sizing


I'm replacing the lower level floor joists in a 135 yr old farm house. Basically sitting 6" off the ground on a rock foundation. The current joists (what's left of them) are rough oak 2x10 on 24" centers. Length = 15.5'. If I go to 16" centers and support them in the middle, would a 2x8 Douglas Fir be sufficient, or should I stay with the 2x10? Flooring will be underlayment then 1x6 pine planking. (similar to original)
THANKS,
--
Steve Barker



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Steve Barker LT wrote:

2x8 will hold but probably will be more "bouncy" even on 16" instead of 24" spacing. If it were me, for that application I'd stay w/ the 2x10 and use treated for the extra moisture resistance and still be far less expensive than Doug Fir (unless you're in the PNW where it can still be found--ask the average worker-bee at the local yards here for "fir" and they'll think "fur" and when you tell them what you mean the response will be "Never heard of it!" :( )
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thanks for your reply and input. Here in the KC area the PT is about a dollar more than the DF in the 2x10x16.
--
Steve Barker



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the years. While you have the floor open, I'd strongly consider doing some digging and making that glorified sleeper foundation into an actual crawlspace with a vapor barrier, and usable access for wiring and such. If that isn't practical, I'd make all the new timbers out of treated wood, and use a solid poured concrete pier up the middle for your center support. I suppose house jacking and a proper foundation are out of the question?
aem sends...
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Raising the whole thing would have been nice, but the "wings" so to speak off the kitchen are on slabs. And it would be cost prohibitive. I've already done about 80% of the wiring and have the plumbing planned and none of it goes under. We even had a guy do a superb job of putting in a high efficiency heat pump/furnace/ac unit with full duct work with minimal hassles. I hadn't even planned for this floor fiasco, but we opened it up to level it and found the joists in a bad way. My preliminary plan for the center support is to dig out the loose dirt and get to some solid ground and lay down a PT 6x6 and block up on top of that. I don't think pouring concrete is possible. I'm on a bit of a time crunch and winter is moving in here fast. I figger if what was there lasted 135 years, then anything I do will out last me for sure. And we plan for this to be the last stop. <G>
thanks for your reply and input,
--
Steve Barker



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