Lowboy Deck Height & Legal Load-Height Limits (2026)

OpenDeck

Sep 25

4 min read

Lowboy deck height planning is the work of matching your trailer's deck to each state's legal load-height limit so tall equipment moves at legal height instead of permit height. Nail it and a 12-foot excavator crosses four states clean. Miss it and one state on the route turns a routine move into an oversize filing everywhere you touch. Whether the trailer itself pays for itself is a separate question — our lowboy worth-it breakdown covers the ownership math — but height is why the trailer exists: there is no federal height limit for commercial trucks, and each state draws its own line.

TL;DR

No federal height limit exists — each state sets its own.
Most eastern states allow 13 ft 6 in; most western states and Texas allow 14 ft.
An 18-inch lowboy deck leaves about 12 ft of cargo height in a 13 ft 6 in state.
Measure deck height loaded — air ride squats under weight.
Permit the load when deck plus cargo exceeds the state limit.

Why lowboy deck height decides your permit bill

Height law in the United States is state law. The Federal Highway Administration states plainly that no federal height requirement exists for commercial vehicles. In practice, most eastern and Great Lakes states cap total vehicle height at 13'6", while most of the West and Texas allow 14 feet. Colorado and Nebraska go to 14'6" statewide, Alaska to 15 feet. Louisiana runs 13'6" off the interstates and 14 feet on them.

Every inch of deck height you save is an inch of machine you can haul without paperwork. That is the entire business case for a low deck.

Deck height	Cargo room in a 13'6" state	Typical trailer
22 inches	11'8"	Standard drop deck well
18 inches	12'0"	Standard lowboy or RGN well
12 inches	12'6"	Low-profile RGN or mini deck

Measure your real deck height, not the brochure number

Start with a tape at the deck's working position, then load the trailer and measure again. Air ride squats under weight, and a trailer that sits 18 inches empty can sit closer to 20 loaded. Quote every load from the loaded number, because the scale house and the bridge clearance both see it loaded.

Measure at three points: the front of the well, mid-deck and over the rear axles where the deck crown is highest. Crowned decks steal a half inch you did not plan for. Write the three numbers on a card in the truck — that card settles more broker arguments than any load board ever will.

Know the limit on every state you cross

Region	Typical legal height
Most states east of the Mississippi	13'6"
Most western states and Texas	14'0"
Colorado, Nebraska	14'6"
Louisiana	13'6" off-interstate, 14' on interstates
Alaska	15'0"

State limits get revised, and designated-highway rules like Louisiana's change the answer mid-route. Confirm the current limit with each state's permit office before the load books — two minutes on the phone cost less than one height citation.

Calculate usable cargo height before you quote the load

The formula is one line: state limit minus loaded deck height equals cargo room. On a 13'6" state that is 162 inches, so a 20-inch loaded deck leaves about 11 feet 10 inches for the machine. A wheel loader standing 12 feet 1 inch with the bucket pinned does not fit — lower deck, fold the ROPS, or pull a permit. Run that subtraction before you commit to the load, not at the shipper's gate.

Pick the deck configuration for the freight

Tracked excavators and dozers ride best on a low-profile RGN well — the 12-to-18-inch deck keeps most machines under 13'6" without permits.
Wheel loaders and telehandlers fit a standard 18-to-22-inch well when the boom folds and the cab clears the math from the step above.
Tall crated freight and tanks may clear on a low deck but still trip a state line — height and width get judged separately at every border.

Permit when the math fails

When cargo height plus deck exceeds the state limit, the load moves on an oversize permit from every state on the route. Permit fees run $15-$50 per state, which we broke down in the oversize load permit cost guide. Past roughly 14 feet in many states the route also pulls escort requirements — the pilot car rules for heavy haul loads cover the thresholds. Price both into the quote before you say yes, because the paperwork never rides for free.

Common mistakes that cost real money

Measuring the deck empty and quoting from the brochure height. Loaded squat eats 1-2 inches.
Forgetting the machine's own variance: ROPS up, exhaust stacks, beacons and whip antennas all add height the bill of lading never lists.
Assuming 13'6" everywhere. Western routes hand you two more free inches; the return leg east takes them back.
Chasing height while ignoring axle weight. Bridge formula limits still apply, and our heavy haul axle-group planning guide walks the spacing math.
Booking before checking route clearances. Some state routes carry overpasses as low as 13'4", under the legal limit itself.