Boat Storage Building: Door Heights, Depth, and What Fits

A boat storage building is a garage or shop sized for your boat on its trailer, so it stays out of the sun, snow, and rain between trips. The honest answer on what size you need is that the hull length on the brochure won’t tell you. The trailer tongue, the motor, and anything mounted up high are what decide the door and the depth.

Here’s how to measure, what to plan for, and what’s worth adding while the building is still on paper. This guide is for a private building on your own property. If you’re developing a commercial facility, see our boat and RV storage facilities page.

Measure the Boat on the Trailer First

Take these four measurements with the boat loaded the way you’d park it:

Measurement	What to include	What it decides
Overall length	Trailer tongue to the back of the motor or swim platform	Building depth
Overall height	Ground to the highest point: tower, T-top, radar arch, or windshield	Door height and eave height
Overall width	Widest point of the boat or trailer fenders, whichever is wider	Door width
Tow vehicle length	Only if you want to leave the truck hooked up	Extra depth or a pull-through bay

Then add working room. You want space to walk around the boat, open compartments, and pull the cover off without rubbing the wall. If you’re planning to buy a bigger boat someday, measure for that one.

Doors Decide Everything

On a boat storage building, the overhead door is the spec that matters most. Go taller and wider than the bare minimum, because backing a trailer through a tight opening gets old quickly.

Several of the boat and RV garages we’ve built use 12 x 14 overhead doors, which handle most trailered boats along with an RV. Keep in mind that the wall has to be taller than the door to leave room for the track, which is why those buildings have 16 foot eaves. Our guide to exterior barn doors compares overhead, sliding, and hinged options and how each one seals.

Don’t forget the approach

A big door doesn’t help if you can’t line up with it. Plan a straight run in front of the door that’s long enough for your truck and trailer, and think about where the snow gets piled in winter. A door on the gable end versus the side wall can change how easy the building is to back into.

Planning the Size of Your Boat Storage Building

Once the boat fits, decide what else shares the space. Most owners don’t build for the boat alone. Three real examples from our projects:

• 40 x 40 x 16 in Greenacres, Washington: two 12 x 14 overhead doors, room for an RV, a boat, and a custom shop.

• 40 x 50 x 16 in Athol, Idaho: a double-bay RV and boat storage garage.

• 36 x 48 x 16 in Spokane, Washington: a metal garage with a 14 x 48 x 11 lean-to, built for winter storage of summer toys.

A lean-to is worth a look if you have a second trailer, a smaller boat, or gear that only needs a roof. Our lean-to buildings guide covers how they attach and what they cost compared to enclosed space. If an RV shares the building, the RV storage building guide covers its clearances, and pole barn sizes shows what fits in common footprints.

What to Add Inside

• A concrete floor. It keeps the trailer level, makes maintenance easier, and keeps ground moisture down. See our pole barn concrete floor guide for thickness and cost factors.

• Moisture control. A boat comes in wet, and an unvented steel building can sweat when the temperature swings. Ventilation and a condensation barrier under the roof steel protect upholstery and electronics. We explain the causes and fixes in pole barn condensation.

• Power. Outlets near the bow and stern for a battery maintainer, lights you can work under, and a circuit for a compressor or shop vac.

• Insulation, if you’ll work in there. Storage alone doesn’t need heat. Off-season maintenance in a Northwest winter does.

• Water and a drain. Handy for washing down, but floor drains are regulated in many areas, so ask your building department before you plan one.

Indoor storage doesn’t replace winterizing. The BoatUS Foundation has solid guidance on getting a boat ready for the off-season.

Boat Storage Building FAQ

How tall does the door need to be?

Taller than your boat’s highest point on the trailer, with margin. Measure it yourself. Towers, tops, and arches vary too much to guess.

Can one building hold a boat and an RV?

Yes, and it’s one of the most common requests we get. Size the doors and eave height for the taller of the two, and give each its own bay if you can.

Do I need to heat it?

Not for storage. A dry, ventilated building does most of the work. Heat is for you, if you plan to do maintenance in the winter.

The Bottom Line

Measure the boat on its trailer, pick the doors first, and size the building around everything else you want in it. Get those three right and the rest is detail.

Steel Structures America designs, engineers, permits, and builds custom boat and RV garages across Idaho, Washington, Oregon, Montana, and Colorado. Give us a call at (800) 833-9997 or request a free quote, and bring your measurements.