Building our box out of wood?

shortbus4x4

Expedition Leader
Who is talking about 4x4's?

They have no business in a camper build. Period.
They barely have any business in residential construction as it is, for a variety of reasons.

If you design such a thickness wall, use 1x or 2x

There is ZERO reason to consider 4x, and many reasons not to.
4x4s posts are for fence posts.

The only place 4x4s belong is under the camper, OP is skipping the 4x4 under the camper and using a 6x6.😉
 

1000arms

Well-known member
Who is talking about 4x4's? ...
I am! :)

... They have no business in a camper build. Period. ...
Incorrect. Period. :) The OP wants a solid and sealed box for a high capacity rig. Rather than go from 2x4 to 2x6 (etc.) the way home construction is often done, using 4x4s is similar to doubling up studs and joists as is often done in home construction. Using the 4x4s allows for greater strength and gluing surface area without reducing interior volume the way stepping up the size of the 2x would if placed in floor,roof, or walls, as there are maximum exterior dimensions the OP plans to follow.

Remember, the OP was considering a 20' container, and wasn't worried about the weight. Although the OP might use thinner skins, the OP could use 4x4s, 3/4" plywood (inside and out), and rigid foam insulation to create a sealed box (using skills the OP has) that probably weighs less than the 20' container idea that was considered (and discarded due to height rather than weight).

I do think 4x4s have no business in most camper construction, but not all. :cool:
[/QUOTE]

I know that most people are trying to build something light enough to work with their particular vehicle, but our MTVR has a 30,000-pound payload capacity, so there may be solutions that wouldn't work for other people, but would work just fine for us.
4x4s posts are for fence posts.

The only place 4x4s belong is under the camper, OP is skipping the 4x4 under the camper and using a 6x6.😉
For most campers, I would agree with you, but the OP's MTVR 6x6 would do quite well with a 4x4-based camper on top! :cool:
 

s.e.charles

Well-known member
4x4 = sure! isn't that why true adventurers carry chain saws & axes?

btw: I noticed the OP didn't have a dedicated Expedition Rated Axe Safe noted on his plans. this should be addressed well ahead of any structural, sheathing, windows, or insulation matters.
 

Alloy

Well-known member
4x material will loose of internal space

Staggering 2x3 on flat for a 2 1/2" wall would limit thermal briding. Like this _ - _ - _ - _ - _ -

Wood structural insulated panels is another option.

Weight should be a concern due to strength of the connections needed to resist the momentum of a heavy structure. Drilling (allot) lightening holes in any solid wood reduces weight and thermal bridging.
 

1000arms

Well-known member
4x material will loose of internal space
Staggering 2x3 on flat for a 2 1/2" wall would limit thermal briding. Like this _ - _ - _ - _ - _ -
Wood structural insulated panels is another option.
Weight should be a concern due to strength of the connections needed to resist the momentum of a heavy structure. Drilling (allot) lightening holes in any solid wood reduces weight and thermal bridging.
4x4s are pretty low quality wood and they warp/twist pretty badly.
I'm not suggesting that using 4x4s for framing is the only option.

I am saying (well, writing) that 4x4s are a possible solution to the OP's question. Although thermal bridging will exist, using 4x4s, glued-in-to-place rigid-foam-insulation, and glued and screwed 4'x8' plywood (to the inside and outside of the 4x4s) allows for a quickly-made solid camper (with a lot of resistance to racking) designed to be mounted to a rig with a 30,000-pound payload capacity.

I know that most people are trying to build something light enough to work with their particular vehicle, but our MTVR has a 30,000-pound payload capacity, so there may be solutions that wouldn't work for other people, but would work just fine for us.
Yes, getting good quality 4x4s would be important, and that might take a bit of effort. :)
 

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Alloy

Well-known member
I'm not suggesting that using 4x4s for framing is the only option.

I am saying (well, writing) that 4x4s are a possible solution to the OP's question. Although thermal bridging will exist, using 4x4s, glued-in-to-place rigid-foam-insulation, and glued and screwed 4'x8' plywood (to the inside and outside of the 4x4s) allows for a quickly-made solid camper (with a lot of resistance to racking) designed to be mounted to a rig with a 30,000-pound payload capacity.


Yes, getting good quality 4x4s would be important, and that might take a bit of effort. :)
4x4s would be advantageous if the box was only going to have 4-6 post supporting the roof......but there is no advantage if the studs are 16" - 24" O.C.
 

1000arms

Well-known member
4x4s would be advantageous if the box was only going to have 4-6 post supporting the roof......but there is no advantage if the studs are 16" - 24" O.C.
Well, what about 3.5" O.C.? No room left for insulation, but hey, the OP's rig can easily handle it. :cool:

I disagree with your statement. :) I think the wide surface of the 4x4s, compared to the thin side of 2Xs, allows for a much larger gluing surface, and allows for better distributing of the loads, especially when the outside and inside 4'x8' plywood-sheets are glued and screwed to two sides of the 4x4s. (I also suggest gluing the rigid-foam insulation to the 4x4s and plywood sheathing.)

That being said (well, written), I don't think the OP would need to go to 16" O.C. if he uses 4x4s for his camper framing. I think 16" O.C. would be a case of diminishing returns, but the advantage of the 4x4's gluing surface would still remain.
 

s.e.charles

Well-known member
plywood in a variety of types is available in sheets up to 12'0". I believe the 16' 0" sheets have a scarf joint. if you have a helper, or are stronger than me, it would eliminate a seam or two.


then there's engineered lumber which has a metric tonne of advantages especially dimensional stability.


don't forget the plethora of framing connectors now required in the coastal regions for hurricane insurance.

the catalog will provoke you to thought: https://www.strongtie.com/



threaded rod and tie rods & turnbuckles being some of my favorite home décor! (seriously; i love this detail)

1588614266768.png
 

MTVR

Well-known member
I did not know about the 16-foot sheets of plywood- that would be advantageous as far as reducing seams. I could get down to a single 16 foot long longitudinal seam, and a slight crown would assist in keeping water from trying to stand on it...
 

Alloy

Well-known member
Well, what about 3.5" O.C.? No room left for insulation, but hey, the OP's rig can easily handle it. :cool:

I disagree with your statement. :) I think the wide surface of the 4x4s, compared to the thin side of 2Xs, allows for a much larger gluing surface, and allows for better distributing of the loads, especially when the outside and inside 4'x8' plywood-sheets are glued and screwed to two sides of the 4x4s. (I also suggest gluing the rigid-foam insulation to the 4x4s and plywood sheathing.)

That being said (well, written), I don't think the OP would need to go to 16" O.C. if he uses 4x4s for his camper framing. I think 16" O.C. would be a case of diminishing returns, but the advantage of the 4x4's gluing surface would still remain.
If greater contact area to resist shear (less of an issue front to back as it is side to side) is needed there is the idea I mentioned before.........."Staggering 2x3 on flat for a 2 1/2" wall would limit thermal briding. Like this _ - _ - _ - _ - _ -"
 

1000arms

Well-known member
I did not know about the 16-foot sheets of plywood- that would be advantageous as far as reducing seams. I could get down to a single 16 foot long longitudinal seam, and a slight crown would assist in keeping water from trying to stand on it...
4'x8' (or cut down), long side vertical for the walls and long side parallel, to the short sides of the camper, for the floor and roof, can be sealed to the framework fairly easily. 16' sheets will require extra work to be sealed where two 16' sheets meet, cost more per square foot, and possibly more difficult to get hold of.

Depending on the work time of the glue one uses, using 4'x8' plywood might be might be a much better choice than larger sheets.
 

1000arms

Well-known member
If greater contact area to resist shear (less of an issue front to back as it is side to side) is needed there is the idea I mentioned before.........."Staggering 2x3 on flat for a 2 1/2" wall would limit thermal briding. Like this _ - _ - _ - _ - _ -"
I think the 4x4s would work better to resist shear, with the greater surface area than 2x3s, and especially when two plywood sheets are butted up against each other and glued-and-screwed to a 4x4.
 
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