Sizing floor joists, and thickness and type of plywood sheeting?

[repete]

I wouldn't rule out I-joists.

I primarily use these in the five homes I have built and shop mezzanine. Straighter, lighter and will accept larger holes the solid wood.

 

[plowhog]

Check out AdvanTech Flooring for a subfloor that is water resistant. Let us know what you think.

Looks like a nice product, but not sure it is available in my area. Seems out of stock for all the stores in my area.

Regarding weather, the area of the mezzanine floor is best considered a "dry location." There are occasional drips here and there in the barn, but none that I know of where the new floor will be located.

 

[dougtrr2]

I would go with the larger joist and overbuild the project. Over time you might be surprised at how much weight you haul up there. And it is dead weight that is constantly there. I don't think you ever hear someone saying I wished I would have built it for lighter duty.

Doug in SW IA

 

[Racer4]

You can also space your joists at 12” oc to get a better rating on 2x8s. I wouldn’t go any less than 3/4” for the floor. Advantech flooring is great, but 3/4” T&G subfloor plywood would work just as well.

 

[Sodo]

I'm thinking of either 2x8 joists, or 2x10 joists, 16" on center. From what I have researched, 2x8 would be the minimum. One tricky part is the joists sitting on the top plate of the outer wall of the barn. The rafters and roof material join at about a 45 degree angle, so "some" of the top corner of the joists will have to be trimmed to allow the joist to slide all the way onto the top plate. With 2x8 I would have to cut less material than 2x10, since less of it would interfere with the rafters and roofing. The added height of the 2x10 would require more cutting trimming. I do not want any center supports

So joists are bearing ontop of the wall plate.
A bevel at the top corners for roof slope will have ZERO effect on the capacity of the joist.

The load carrying capacity of your mezzanine joist is determined by the joist height (8" or 10") at the midpoint (7'3") of the 14'6" span.

The bevel at the ends makes no difference.

 

[Alan W.]

https://www.weyerhaeuser.com/application/files/3215/4223/2335/LB-4026.pdf

Heres a span chart that might help you.

 

[ning]

Looks like a nice product, but not sure it is available in my area. Seems out of stock for all the stores in my area.

While it's a completely different product area, an organization I'm involved with has a need for a particular plywood, and due to circumstances that began in '22 the product's availability is sketchy. We were able to get some at local (50mi range) stores the first two years but last year I couldn't find it locally.

I was able to order some from far away and given a decent order size even with the LTL shipping it was less than the (out of stock, don't know when it would get in if ever) locals wanted, per sheet.

Kinda doubt that the price thing would hold for a more typical product but you should price out getting some shipped as it'll land in your driveway, which was worth a lot to me as I wouldn't need to take half my day getting it either...

 

[quicksandfarmer]

Looks like a nice product, but not sure it is available in my area. Seems out of stock for all the stores in my area.

Regarding weather, the area of the mezzanine floor is best considered a "dry location." There are occasional drips here and there in the barn, but none that I know of where the new floor will be located.

Other brands are LP Legacy and DryGuard by Georgia Pacific. What you want is something with a "no-sand" warranty, they're guaranteeing that if it gets wet it won't swell and require sanding to get it smooth again. It's usually expressed in how many days it can be exposed to the weather without problems, about six months is typical.

They aren't waterproof but they are pretty water-resistant.

 

[caver]

I primarily use these in the five homes I have built and shop mezzanine. Straighter, lighter and will accept larger holes the solid wood.

Yep I was reluctant at first but they can have a longer span than a traditional joist if you can go taller. Modern lumber is garbage.

 

[CalG]

Strength often takes much less material than does acceptable stiffness. Deflection is an important part of any consideration.