I was looking up the legal DOT heights (13.5ft) as well as the minimum recommended clearance between truck and bottom of the 5th wheel overhang (6in) then crossed it with the most recent height measurements for Ford trucks (no bias, just the first one I could find).They don't have a direct measurement to the top of the bed but they had a measurement from open tailgate to ground 36.9in (F350 biggest wheelbase) then a height from the bottom of the bed to the top 21.1in, totaling 58in.Adding the 6in for bed clearance - 64in.Now take the federal max height 13.5ft (162in), and minus 2in (personal choice for peace of mind) which leaves 160in.Minus the 64in and that leaves you with 96in or 8ft.My question is, if you take off an extra foot for insulation and structuring (would be a bit excessive but using it for a more conservative outlook), could the interior of the overhang portion of the 5th wheel be 7ft?

Good question. But why 7 ft for the bedroom (in most 5th wheels)?I just measured our floor to ceiling in our 2022 Grand Design Solitude 378 MBS bedroom and it is 6.5 ft (78").

I am thoroughly confused. If you want to know your air draft simply measure from your highest point to the ground while hooked up.How difficult is that?

Veebyes wrote:I am thoroughly confused. If you want to know your air draft simply measure from your highest point to the ground while hooked up.How difficult is that?Unnecessary, but this is theoretical, I don't have a unit, but am planning a build and want to know if my theoretical numbers make sense.

Cptnvideo wrote:Good question. But why 7 ft for the bedroom (in most 5th wheels)?I just measured our floor to ceiling in our 2022 Grand Design Solitude 378 MBS bedroom and it is 6.5 ft (78").I figured there is about 6ft or so for the overhang, which would make the dimensions of that space, 8'w by 6'd by 7'h. So a decent room.Plus I'm 6ft2in so though 6ft6in isn't too bad, it's right above my head haha.

4" above your head sounds fine for a room that is only used for sleeping and getting dressed.

Theoretical heights. | Good Sam Community

30 Replies

Second_Chance
Explorer II
May 12, 2022
Someone with a CDL and experience straightened me out on this on another forum recently. There is no such thing as a legal "DOT height" from the Federal government. 13'6" is the minimum height for overpasses on the interstate highway system. Some states have their own regulations. That said, there is no such thing in my books as a "theoretical height." The only thing you can rely on is an actual measurement with the trailer on the truck on level ground.

Rob
Cummins12V98
Explorer III
May 12, 2022
I am 13' 4" at highest point, my top of tailgate is 55" loaded or not and have 6" bed clearance. Never heard of anyone being higher.
ACZL
Explorer
May 12, 2022
My '17 F350 DRW 4x4, CC w/ 8' box and '18 Big Country comes in at 13'4" last time I measured it. The national bridge height is 13'6" not 13'5". BUT there is a built in add'l foot on MOST bridge clearance heights. We still have 6" of clearance from top of box to underside of 5er. One thing you have to take into consideration (unless you have airbags) is that the rear of the truck will squat down w/ 5er on so this brings down the top front height of your 5er. RV transporters don't have problems and they have all kinds of truck configurations. Just sayin'.
way2roll
Navigator III
May 12, 2022
I am also confused. Are you building a FW from the ground up? I am sure specs/dimensions are readily available for most production units. Why live in theory, go to an RV dealer and take measurements.
MNRon
Explorer
May 12, 2022
There's usually an AC on top of that roof that you haven't accounted for
Cptnvideo
Nomad
May 12, 2022
4" above your head sounds fine for a room that is only used for sleeping and getting dressed.
MatthewThomas
Explorer
May 12, 2022
Cptnvideo wrote:
Good question. But why 7 ft for the bedroom (in most 5th wheels)?
I just measured our floor to ceiling in our 2022 Grand Design Solitude 378 MBS bedroom and it is 6.5 ft (78").

I figured there is about 6ft or so for the overhang, which would make the dimensions of that space, 8'w by 6'd by 7'h. So a decent room.

Plus I'm 6ft2in so though 6ft6in isn't too bad, it's right above my head haha.
MatthewThomas
Explorer
May 12, 2022
Veebyes wrote:
I am thoroughly confused. If you want to know your air draft simply measure from your highest point to the ground while hooked up.

How difficult is that?

Unnecessary, but this is theoretical, I don't have a unit, but am planning a build and want to know if my theoretical numbers make sense.
Veebyes
Explorer II
May 12, 2022
I am thoroughly confused. If you want to know your air draft simply measure from your highest point to the ground while hooked up.

How difficult is that?
Cptnvideo
Nomad
May 11, 2022
Good question. But why 7 ft for the bedroom (in most 5th wheels)?
I just measured our floor to ceiling in our 2022 Grand Design Solitude 378 MBS bedroom and it is 6.5 ft (78").

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Theoretical heights.

30 Replies

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