What size should an RV garage be?

The right RV garage size starts with your coach, then adds clearance on every side. For a large Class A motorhome, plan a 14 to 16 foot tall door, a 16 to 18 foot interior ceiling, a bay 14 to 16 feet wide, and a depth of 40 to 50 feet. Those numbers fit a long diesel pusher with rooftop air conditioners, satellite domes, and slide-outs, plus room to walk around it and open the door. A smaller Class C or travel trailer needs less, but the rule is the same: measure your actual RV, then add room to move. The most common and most expensive mistake is building a door an inch too short, so measure the height with the rooftop gear in place before you pour a slab.

Below are the real dimensions by RV class, how the door and ceiling work together, and how Arizona height limits shape what you can build.

RV garage dimensions by motorhome class

Match the garage to your RV class, since a Class A and a Class B sit at opposite ends of the size range. The RV Industry Association (RVIA) supports a maximum recreational vehicle length of 45 feet and a maximum width of 102 inches (8.5 feet) plus up to six inches for items like mirrors and awnings. That width standard is why a single RV bay needs to be wider than a normal car bay. Here is what each class needs inside the garage, with clearance added:

• Class A motorhome (the big bus-style coach, 30 to 45 feet long): door 14 to 16 feet tall, ceiling 16 to 18 feet, bay width 14 to 16 feet, depth 40 to 50 feet.
• Class C motorhome (the cab-over van-front coach, 22 to 33 feet): door 12 to 13 feet tall, ceiling 14 feet, bay width 12 to 14 feet, depth 30 to 40 feet.
• Class B camper van (10 to 12 feet tall): door 10 to 12 feet, ceiling 12 to 13 feet, depth 25 to 30 feet.
• Fifth wheel or travel trailer with a tow vehicle: door 13 to 14 feet, ceiling 15 to 16 feet, depth 45 to 55 feet so the truck and trailer fit hitched.

These are planning targets, not exact rules. Your coach has its own numbers on its data plate or in the owner manual. Use those, then add the clearance below.

How tall the door and ceiling need to be

The door height and the ceiling height are two separate numbers, and you need both right. A large Class A motorhome runs up to the legal road height of 13.5 feet, and that height already includes rooftop air conditioners and vents on most coaches. A 14 foot door clears a 13.5 foot coach with six inches to spare, which is the practical floor for a big motorhome. Many Arizona owners go to a 16 foot door so they never have to think about it and can fit a future taller rig.

The ceiling has to sit higher than the door. A 14 foot door needs the header above it, the door track, and the opener, so the interior clear height runs 16 to 18 feet. That extra space lets the door panels roll up out of the way and gives you room to work on the roof of the coach, clean the air conditioners, or reach a vent. If you plan a car lift or overhead storage, add even more. Skimping on ceiling height to save on wall block is a false economy, because you lose the working room that makes a tall garage worth building.

Width and depth round out the box. A single RV bay at 14 to 16 feet wide lets you open the slide-outs and the entry door and still walk past. Depth at 40 to 50 feet fits a 45 foot coach with room at the nose for a workbench and at the tail to close the door. If you store a tow car or a boat in the same bay, add its length to your depth.

Arizona height limits that cap your design

Local zoning caps how tall an accessory building can be, and a tall RV garage with a 16 to 18 foot ceiling can approach that cap, so confirm your limit before you design. In unincorporated Maricopa County, which covers rural areas like the Rio Verde Foothills, a detached accessory building in rural and single-family residential zoning may reach a maximum height of 30 feet. That is usually enough for an RV garage, since an 18 foot interior plus the roof structure still clears 30 feet on a low-slope roof. A steep gable on an already-tall building gets closer to the cap, so the roof pitch becomes a real design choice.

Cities set their own limits and some residential zones cap accessory buildings below 30 feet, so pull the zoning for your exact lot. Setbacks matter too. In unincorporated Maricopa County, a detached accessory building may not sit "nearer than three feet to any side or rear lot line" and may not "occupy more than 30% of any required yard." A 50 foot deep RV garage takes a big bite out of a yard, so the 30% rule and the setback can decide where it fits even on acreage. A homeowners association can add its own height and material limits on top of the zoning. For a full cost picture once the size is set, see our guide on the cost to build an RV garage in Arizona.

Clearance and code details people miss

A few dimensions come from the building code and from how you actually use the garage, not just the coach size. Under IRC Section R309, a private garage floor must be a noncombustible surface like concrete and slope toward the vehicle door to drain liquids. That slope matters on a deep RV slab, because a long, flat floor holds water and washdown runoff. Plan the drainage into the slab pour.

Add working clearance around the coach, not just enough to squeeze it in. Leave two to three feet on each side so you can open bay doors, walk the length, and run a hose or a cord. Leave three to four feet at the rear for the slide-out and storage bays, and enough at the nose to stand and work. A coach that barely fits is a coach you cannot maintain. Slide-outs on a Class A can push the coach two to three feet wider on each side when they are open, so a bay sized only to the closed width leaves you stuck. If you ever want to wash or wax the roof, you also want headroom above the slides, not just beside them.

If the RV garage is attached to or shares a wall with the house, IRC Section R302 requires a fire separation between the garage and living space, usually half-inch gypsum board on the garage side, and a self-closing, tight-fitting door between them. That separation does not change your RV dimensions, but it does change the wall and door details on an attached design. Get the coach measurements, add the clearances, check your zoning height cap, and a builder can turn those numbers into a garage that fits the rig you own now and the one you might buy next.

Where Jematell Homes comes in

Clear allowances and an honest cost breakdown are how we start every custom home. We would rather answer your questions before you build than after, so get in touch any time.

Sources

• RV Industry Association (RVIA): RV Dimensions policy (length and width standards)
• ICC IRC 2018 Section R309 (Garages and Carports)
• Maricopa County: Accessory Structures, Equipment, and Setbacks (height and setback rules)
• ICC IRC 2018 Section R302 (Dwelling-garage separation)