Citrus Growers Forum

brianPA2 · Posted: Tue 26 Nov, 2013 1:27 am

bussone wrote:

brianPA2 wrote:

My joists measure 9" thick with 16" on center spacing. I think the 9" is actually 9.25" which means 2x10 lumber.

I am having a really hard time finding a calculator that tell me load capacity for a span, instead of the reverse. But it seems that 2x10 construction can handle at least 20lbs/sq ft static load over a 10ft span. 20ftx24ft is 480sq. ft. which is 9600lbs.

9600/8.3 (lbs/gal water) = 1156gallons of water or 21 55gal drums or 231 5gal buckets.

Uh, I must have done some math wrong either way earlier or just now as that is more than enough. I'm glad you mentioned this.

I have been looking into phase change materials and they look too expensive anyway. Glauber's salt and similar materials are supposedly unstable over time and separate, losing effectiveness. I think water will have to do after all.

EDIT: I think the limitation is the middle support beam and not the joists themselves. I don't think adding unnecessary weight is a good idea.

It's a lot of weight.

Basically: would you park two sedans in your attic? Because that would weigh about the same amount. There's a reason your garage floor has a 12" concrete pour. =)

Yeah, I've decided against any thermal mass. Partly because it seems pointless without a large enough heater (it would slow the roots warming up >55F when the sun comes out if they've been in the 40s-50s all night) and because of the weight reasons.

I have my pots sitting on empty buckets right now and they seem to warm up fast enough.