floor framing: 2x2 vs. 2x4?

[nikwax]

I see that some of your frame your floors with 2x2 and others use 2x4. What advantage does 2x4 give over 2x2 framing? 2x4 is obviously heavier. I'm using 1/2" ply for flooring.

[Arne]

I used 3/8 on top, with 2x3's and 1/8 on the bottom with full foam insul in between..

The strength comes from the 1/8 on the bottom....

what spacing are you using.... ?

I put a piece of 3/4 ply between 2 boards and stepped on it.. very rigid...

I put a piece of 1/2 ply between 2 boards and stopped on it... not very rigid.

I'd try that and it will give you an idea of what your spacing should be.

[Roly Nelson]

I'm afraid I went a bit overboard on my first build. I used 2x4s, bolted to frame longitudinals and cross members. If I were to do it again, it would be 2x2s over metal members and only heavier lumber where spans from side to side are involved, not bolted to solid steel. My personal feeling about floor thickness is that most floors are way too thick. We never stand on these floors, rarely kneel on them, and just sit or lay on them with a mattress below us. My first floor was 3/8", the second floor was simply an 1 3/8 hollowcore door with 1/8" skins. Works fine for me. Just my 2 cents.

Roly, (why is there no "cents" key on the keyboard, just a $$$$ key)

[Kens]

I did 2x2 with 1/2" ply remember you dont walk on it you lay on it.

[halfdome, Danny]

It depends if you flush your walls with the chassis or you hang the walls to cover the chassis. You'll need wider wood to cover the chassis but anything 2" (1 3/8") is too thick in my opinion unless you don't want to purchase 1" Popular like I did. I prefer Popular over 2nd or 3rd growth Hem/Fir, it just doesn't have the strength as Popular, but to each his own. Danny

My 2,000th Post

[Micro469]

I used 1x2's with 3/8 ply top and bottom, filled with 3/4" styrofoam. Very solid.. I haven't fallen through yet...

[nikwax]

I should have been more specific: I'm building a Puffin-like trailer, so I will be standing on some of it. I may just follow Steve W's build with 2x4 or at least lay out the plywood and walk around on it with different combos.

[Gerdo]

2x2s are plenty. 2x4s are overkill!

[Miriam C.]

I think Steve build his with heavier because he is standing and was over the wheels by 12" on each side. More support needed there.

[steve wolverton]

:thumbsup: I think Steve build his with heavier because he is standing and was over the wheels by 12" on each side. More support needed there.

Miriam is exactly right. The only reason I used 2x4's is because they had to support the extra 12" overlapping the sides of the camper. For what it's worth, I was crawling around under the Puffin last night and I'm very happy with the way it's holding up. Nothing looked bent, warped, or even strained. I should have used 2x2's and that would have cut the weight in half.

[Arne]

I would have used 2x2s, but used 2x3s instead because I will be bolting things to them, like frame supports.... I only have 1 metal xmember in front and one in back, so middle of floor has no metal under it. I was concerned about the frame falling in (twisting) from suspension side stress, so am going to triangulate with a metal strap from frame bottom to floor,, ergo, the 2x3s in certain areas.

[Gerdo]

Mine is 2x2s. I only sandwiched under the sleeping cabin and a single floor under the galley. I could get away without a sandwich floor under the galley because it is 3/4" thick (this is where I could have saved alot of weight, I used 3/4" FRP plywood for both the top and bottom of the sandwich)

[nikwax]

:thumbsup: I think Steve build his with heavier because he is standing and was over the wheels by 12" on each side. More support needed there.

Miriam is exactly right. The only reason I used 2x4's is because they had to support the extra 12" overlapping the sides of the camper. For what it's worth, I was crawling around under the Puffin last night and I'm very happy with the way it's holding up. Nothing looked bent, warped, or even strained. I should have used 2x2's and that would have cut the weight in half.

Hi Steve,


So even with the overhang, you'd do 2x2?


Going over the Lil Guy article, he used 2x2 as well. Hmm.

[steve wolverton]

So even with the overhang, you'd do 2x2?
Going over the Lil Guy article, he used 2x2 as well. Hmm.

2x2's would be plenty as the weight is also displaced through the plywood floor. You're only supporting 12" of overhang with the 2x2 (or 2x4) as the trailer frame is supporting the bulk of the weight.

I did the math on it somewhere in the forums, and each 12" of overhang ended up supporting 15-20 pounds or something like that. I'd be willing to bet that if you screwed a 2x2 onto a picnic table with 12" sticking over the edge, and began stacking weight on it, you'd be surprised how much it would hold - and that's without the addtional strength of the plywood flooring that would allow even more weight.

[Arne]

The front and back support the walls, and the wall and frame only have 12" of wood, so no problem...

Think of it as a box. The front and back wall straddle the frame and they support the walls.... it would take a lot to distort that overhang.