A 20×40 metal building kit encloses 800 square feet, a footprint 20 feet wide and 40 feet deep. That holds two vehicles parked side by side, a two-bay garage with a workshop behind it, or a single long run of covered storage deep enough to swallow an RV, a boat, or a line of farm equipment. At 800 square feet it crosses out of single-car-garage range and into real workshop and small-barn territory.
This guide sits under the metal building sizes pillar, and it covers one footprint in depth: what fits inside the 800 square feet, the jobs a 20×40 does well, the frame and options you will see on a quote, the clear heights you can order, and an illustrative 2026 price range. For every footprint side by side, the metal building size chart lays them out.
800 square feet
What fits in a 20×40 metal building
Twenty feet of width is a true two-car span, and the forty-foot depth is what sets this size apart. Park two vehicles side by side and keep a back zone for a bench, or run one long lane that holds a vehicle, a boat, and a shop in a row. If 800 square feet is more depth than you need, a 20×30 trims it to 600; if you want a wider clear floor instead, a 30×40 adds ten feet of width.
| What you want to store | How a 20×40 handles it |
|---|---|
| Two cars side by side | Both fit with a center aisle and walk-around room |
| One car plus a workshop | A bay parked up front, a full bench and shop across the rest |
| RV or large boat | A length up to roughly 38 feet ‹confirm› clears if the door height matches |
| Farm or yard equipment | Tractor, mower, and a utility trailer under one roof |
| Two-car garage plus storage | Both vehicles plus a back wall of shelving or a loft |
| Finished room, gym, or studio | Insulated, 800 sq ft reads as a real room, not a closet |
What clears at this size. A 20×40 is two lanes wide with depth to spare in each.
Common uses
What people use a 20×40 for
The 800-square-foot footprint sits in a sweet spot: roomy enough to combine two jobs under one roof, small enough to stay affordable and DIY-friendly. The uses it does best:
- Two-car garage. Park two vehicles side by side with room to open both doors and walk the perimeter. See metal garage kits for the garage-specific build.
- Garage plus workshop. One bay for a vehicle and the rest for a bench, tools, and a project. This combo is the headline reason buyers size up to a 20×40.
- RV, boat, or trailer storage. The 40-foot depth swallows most RVs and trailered boats out of the sun and weather, provided the door height clears them. For more on matching the building to the job, see what people build with steel.
- Farm and equipment barn. A tractor, a mower, implements, and a trailer in one dry, lockable building, with depth for a feed or tack corner.
- Hobby or commercial shop. Woodworking, welding, auto work, or a small trade shop. With a finished interior it works as a studio or a home gym, and as a shell it underpins a small metal building home project.
Frame & options
The frame and options on a 20×40
At a 20-foot span you sit on the line between two frame types, so a 20×40 is the first common size where you choose. Light buildings come on galvanized tube steel; stouter, certified buildings come on red iron, the structural I-beam that carries wider clear spans and heavier loads. Frames are sold by wall thickness in gauge, where a lower number means thicker steel. A 14-gauge tube frame is the budget option, 12-gauge is the upgrade ‹confirm›, and red iron is the step up for snow country or a fully certified build.
Past the frame, a 20×40 quote is a menu, and at this size the choices move real money:
- Doors. One or two roll-up garage doors for the bays, plus a walk-in door so you are not lifting a big door every trip. A taller RV door changes the eave you need.
- Wall enclosure. Fully enclosed, partly open, or a mix. Enclosing all four sides turns the shell into a lockable, finishable building.
- Insulation. Needed if you will heat the space year-round as a shop, gym, or studio. Skip it for cold storage or a cold barn.
- Roof style. A vertical A-frame roof sheds snow and water better than a rounded roof and looks more like a house garage, for a modest premium.
Get it stamped for your county
An 800-square-foot building is large enough that most counties want a permit and a rated foundation. Order the kit certified for your local snow and wind loads, and tie it to the slab or footings the engineering calls for. The base spec is not the certified spec, so confirm the load rating in writing ‹confirm›.
Clearance
Height and door clearance
Floor space gets the attention, but eave height is what decides whether a tall truck, an RV, or a lift fits. Order the height around the tallest thing going inside, not by default. The numbers to anchor on:
- Eave height. A 20×40 is commonly offered with side walls from about 9 to 14 feet ‹confirm›. Nine feet handles cars and pickups; go to 12 to 14 feet if you want to store an RV, run a car lift, or add a loft.
- Door height. A standard 8-foot roll-up clears most trucks. An RV, a boat on a trailer, or a topped truck may want a 10 to 12 foot door ‹confirm›, which in turn drives a taller eave.
- Roof peak. A vertical A-frame roof adds height at the center for hanging storage or a partial loft, while a rounded roof keeps the profile low.
The trap is ordering a short building, then finding the RV will not clear the header. Measure the tallest thing going inside, add a foot of margin, and size the door and eave to that. The how to choose a size guide walks the measuring step before you buy.
Cost
What a 20×40 kit costs in 2026
As an illustrative 2026 range, a 20×40 steel shell kit lands roughly between $9,000 and $20,000 ‹confirm›, before concrete, delivery, and permits. An open or partly open cover on a light tube frame sits near the bottom; a fully enclosed, certified red iron garage with two doors, taller walls, and a vertical roof sits near the top. The frame type, the gauge, the eave height, and the door package drive most of the spread.
Those are shell numbers, not turn-key. A concrete slab, site prep, insulation, and any wiring are separate, and on a finished shop they can rival the kit price. For how the dollars break down across sizes and options, see the metal building kit prices pillar, which covers the cost side in full.
Treat any single figure with care, because prices move with the steel market, your location, and the season. Since a 20×40 sits near the top of the small-to-mid range, it is worth pricing a 30×40 in the same call, where the cost per square foot often drops, and the larger sizes if your plot allows. Confirm the gauge and the load rating before you commit ‹confirm›.
FAQ
20×40 metal building: common questions
How many square feet is a 20×40 building?
A 20×40 building is 800 square feet, found by multiplying 20 feet of width by 40 feet of depth. That is enough for a two-car garage with a workshop behind it, or one long run of covered storage for an RV, a boat, or equipment.
How many cars fit in a 20×40 metal building?
Two side by side, with room to open the doors and walk around them, plus depth left over for a bench or storage. Because the building is 40 feet deep, you can also park two cars end to end in one lane and keep the other lane open for a shop.
Will an RV fit in a 20×40 building?
Often, if you order the height to match. The 40-foot depth clears most RVs and trailered boats up to roughly 38 feet ‹confirm›, but the roll-up door height is the real limit. Order a 12 to 14 foot eave and a tall door so the unit clears the header, not just the floor.
What frame does a 20×40 kit use?
It depends on the build. A light, partly open 20×40 comes on galvanized tube steel; a fully enclosed or certified building comes on red iron, the structural I-beam used for wider spans and heavier loads. In snow or wind country, the red iron and the heavier gauge earn their cost.
How tall can a 20×40 building be?
Side wall, or eave, heights of about 9 to 14 feet ‹confirm› are common at this size. Nine feet suits cars and pickups; order 12 to 14 feet if you want an RV, a car lift, or a loft. The eave height sets how tall a door you can hang.
How much does a 20×40 metal building cost?
As a 2026 illustration, the bare shell kit runs roughly $9,000 to $20,000 ‹confirm›, depending on frame type, gauge, eave height, doors, roof style, and the certified load rating. A slab, delivery, and insulation are extra. Always get a written quote stamped for your location.
Do I need a permit for a 20×40?
Usually yes. At 800 square feet on a permanent foundation, a 20×40 crosses the permit threshold in most counties. Check with your local building department before you order, since the answer also shapes your foundation, your tie-downs, and the certified load rating you need.
Related guides
Keep reading
Comparing this footprint against its neighbors and the hubs that put it in context:
- Metal building sizes: the complete guide (the parent pillar).
- 20×30 metal building kits and 20×24 metal building kits (the smaller sizes in this width).
- 30×40 metal building kits (step up to a wider, true multi-bay floor).
- 24×36 metal building kits (a similar area in different proportions).
- Most popular metal building sizes (where the 20×40 ranks).
- Metal building size chart (every footprint and its uses in one table).
