1/2" plywood vs 3/4" plywood

[CampingOdyssey]

Hi everyone, I'm putting in a floor and some cabinets in my minivan. I'm wondering what thickness is best to use 1/2" plywood or 3/4"?

In the back where I'm doing the build, I took out the carpet. In that area, the back 1/2 of the floor is pretty flat but the other half (where the middle seats were), that whole area dips down about 3/4" of an inch with multiple seat hooks sticking out of the ground. I was going to lay the plywood all the way across the flat part and the part where the hooks are, since they're about even. I have some insulation that I'll put in the area around the seat hooks and may lay some thin insulation on the flat part or just leave it bare. For the layout, I'm leaving it mostly open (no bed or sofa). About 34" of floor space and about 18" of cabinets along one side. I won't be able to walk on it, but I'll be crawling and moving around on my knees. I was going to go with 3/4" but it seems like it might be overkill. Would 1/2" be ok in that situation? Was thinking where I have my battery, I may double it up to an inch, but the rest of the build keep it at 1/2"? What do most van builds use? Thanks for the help!

 

[maki2]

1/2” will work unless you have a wide span over an area without support from the vans structure and are putting a lot of weight over that area. Your body weighs a lot.

 

[Spaceman Spiff]

^^ Agree.
You can add some support over the cavities where the seats were (a second layer of 1/2" would work well).

 

[eDJ_]

In my experience 1/2 inch should work for an average weight young person. (under 200 pounds) Above that weight I'd suggest 3/4 inch plywood.

I've seen some use lattice wood strips between the metal floor's raised ribs to reinforce a thin flooring. But for all that trouble & expense it may be better to use 3/4 inch plywood.

But 1/2 inch should be a minimum.

 

[NctryBen]

They use 1/2” on roofs and with trusses 2’ apart it isn’t to bad to work on. Usually usb sheeting... that’s hauling up bundles of shingles and everything. My concern would be if you were putting down a flooring on to of that. Like peel and stick vinyl might or probably wouldn’t hold up. I imagine you’d do something...

 

[user 37446]

Back after a 2 year absence... (Used to be TWIH)
Anyway, 1/2 and 3/4" (or 5/8 even) are good, thicker allows more "purchase" for wood screws to grab so as to keep things from moving. It's not like the additional 1/8 or 1/4" is going to cause you an issue on weight or height. Cost is a lot more for 3/4" CDX than 1/2" but that shouldn't always be the main consideration.

 

[afblangley]

Another option is to lay 1/2 rigid foam board across the metal floor and 1/2 plywood on top of that. In addition to its insulating qualities, foam board is a vapor barrier and provides sound deadening.

If there’s a chance you’ll appreciate the utility of being able to reinstall the seats on occasion, you can build the floor up leaving a cutout for the seat hooks (and cargo tie downs) and lay a thin piece of plywood across it to create a flat floor when not in use. This is what I did in my passenger van.

 

[user 37446]

Good ideas, especially GM full sized vans which I have read/seen have hard to remove seat brackets.

 

[Malamute]

I cant imagine 1/2" not being enough on a vehicle floor. If theres any noticeable flex from a concentrated weight point you can run the strength axis cross ways instead of length ways in the vehicle, in other words, the greatest resistance to flex in plywood and OSB is with the piece going long ways across the gaps. That would entail cutting it and youd have a seam at 4' from whatever end you started from. Plywood of a given thickness is more rigid than OSB and holds screws better. I also believe it outgasses much less than OSB.

I used to always throw a sheet of 1/2" plywood (not OSB) on my pickup bed floors to make them level and protect the metal floor from the abuse they usually get.

Im not aware of anyone using 1/2" ply or OSB on roof sheathing unless a cheap house, everyone I know uses 5/8". The difference is quite noticeable in the amount of flex with 24" centers on rafters or trusses. 3/4" is only used on sub-floors as far as I know, and its quite heavy. That would be bridging 16" floor joists, with whatever finish floor going over that. If for any reason I were to upsize from 1/2" id go 5/8. not 3/4. The only reason Id use 3/4 would be on a subfloor of a house with 16" spacing of supports and you were going for code floor load ratings.

 

[BelgianPup]

I can't imagine any spot in a mini-van being so large that 1/2" plywood wouldn't support most humans.

The weight of a sheet of 1/2" plywood ranges from 48 to 68 lbs (depending on type of wood. The weight of 3/4" ranges from 70 to 88 lbs.