How to Choose the Right Steel Building Kit Size

Most steel building size mistakes come down to four numbers: width, length, eave height, and door size. If I get those four right from the start, I’m far less likely to pay for space I don’t use – or end up with a building that feels too tight the day it goes up.

Here’s the short version: I start by measuring the largest vehicle or machine, then I add room for walkways, work areas, storage, and future growth. After that, I check setbacks, height limits, lot coverage, driveway access, and turning space before I lock in a kit size.

A few numbers from the article stand out:

9–10 feet per vehicle is a good planning range for side-by-side parking.
3–4 feet works for pedestrian aisles.
12–13 feet is a common forklift aisle width.
I should add at least 2 feet above the tallest item to estimate eave height.
Door height is often about 2 feet less than eave height.
Adding 20–30% more space helps with storage growth and circulation.
A 2-foot sidewall height increase can add about $1–$2 per sq. ft. to cost.
Adding 4 feet of eave height may cost about 8–12% more, while giving about 25–35% more usable storage space.

If I had to boil the whole article down to one checklist, it would be this:

Measure first
Sketch the layout
Check the site
Set width, length, and height
Match doors to the biggest thing going inside
Leave room for later

In other words: I shouldn’t shop by “standard size” first. I should shop by what has to fit, how I’ll move inside the building, and what the lot allows.

How to Choose the Right Size Metal Building RV Boat and Equipment Storage Guide

Measure what must fit inside before choosing dimensions

Measure your biggest items first. Guessing is how people end up with a kit that looks fine on paper but doesn’t work once it’s built.

List vehicles, equipment, storage, and work areas

Start with vehicles and heavy equipment. They set the minimum floor space. After that, add storage areas, work zones, and the clearance needed to move around everything.

Measure vehicles and trailers with mirrors, racks, and roof units attached. Those small add-ons can change door width and eave height more than people expect.

Clearance is where buyers often come up short. A 10-foot machine may need a 20 × 15-foot work zone once you add operator space, staging, and room for maintenance. For vehicles, plan for at least 9–10 feet of width per vehicle so doors can open fully and people can walk around without squeezing. Pedestrian aisles between zones should have at least 3–4 feet of clear width. If you’re using a forklift, standard aisles increase to 12–13 feet.

Item	Space to Plan For
Sedan	14.7 ft long × 5.8 ft wide × 5–6 ft tall
Pickup truck	16–20 ft long × 6.3–6.8 ft wide × 6 ft tall
RV	12–35 ft long × 7–8.5 ft wide × 8–13 ft tall
Pallet (floor stacked)	8–10 sq. ft. per pallet
Pallet (racked with aisle)	12–15 sq. ft. per pallet, including aisles

Sketch the floor plan on paper first. It’s a simple way to spot problems before they turn into expensive ones. Mark where each item goes, how people move through the building, and where storage may spread over time. Then check that layout against setbacks and height limits.

Check site limits, setbacks, and local code requirements

Once you’ve mapped the inside, make sure the lot can handle it. Your lot size is not the same as your buildable area. Setbacks, easements, and lot-coverage rules can cut down the space you can use. Many counties also cap lot coverage, which can limit your maximum square footage before you even choose a kit.

Height limits matter too. They can affect your eave height or roof pitch. Call your city or county building department before you lock in dimensions. Ask about:

Setbacks
Height limits
Easements
Drainage requirements

Requirement	What It Affects
Setbacks	Maximum width, length, and placement on the lot
Height limits	Maximum eave or peak height
Lot coverage rules	Maximum total square footage
Easements	Where the building can be positioned
Drainage and slope	Usable area and foundation planning

If you’re storing long trailers or large equipment, check the driveway approach and turning radius before finalizing door placement and building orientation.

Convert your space needs into width, length, and height

Steel Building Size Guide: Dimensions by Use Case

Turn your space estimate into three dimensions: width, length, and height. Each one does a different job. If one is off, the others can stop working the way you need.

Choose width and length based on your use case

Start with width. It controls how much side-by-side room you have, and it’s the most expensive dimension to increase because it needs heavier framing. That matters fast when you’re trying to park vehicles, open doors, move tools around, or leave room to walk.

A good rule is to leave 2 to 3 feet of walking clearance on each side of a vehicle or piece of equipment. For one vehicle plus a small work area, 20 feet wide can work. If you’re parking two full-size trucks or SUVs, you usually need at least 24 feet of width, while 30 feet gives you more breathing room for doors and movement.

Length is usually easier and cheaper to add. Most buildings add length in 10- or 20-foot bays, which makes it a more budget-friendly way to grow than width. Extra length also helps with storage rows and tandem parking, so the main bay doesn’t get blocked.

Use Case	Recommended Footprint	Practical Capacity
Basic storage	20 × 30 ft	1–2 cars + small workshop
Standard garage	24 × 30 or 24 × 36 ft	2 cars with deep storage or hobby space
Mixed-use shop	30 × 40 ft	3 cars, or 2 cars + dedicated work zone
Large equipment	40 × 60 ft	Full contractor shop or farm machinery

Set height for equipment clearance and headroom

Once width and length are set, height becomes the detail that can make the whole plan work – or fail. It’s also the part buyers most often underestimate, and one of the hardest things to fix later.

The best way to size height is simple: start with your tallest item. Measure its full height, including roof-mounted AC units, racks, or antennas. Then add at least 2 feet. That gives you your minimum eave height.

Door openings also need room for the header and roll-up hardware, so they should be about 2 feet shorter than the eave height. In plain terms, if you need a 12-foot door for an RV or tall trailer, you need at least a 14-foot eave.

For most passenger vehicles and small trucks, 10- to 12-foot eave heights are common. An RV or fifth wheel usually needs 14- to 16-foot eave heights. If a vehicle lift might be in your future, it’s smart to build for 14- to 16-foot eave heights from day one.

Equipment	Door Height Needed	Required Eave Height
Passenger van / SUV	8 ft	10 ft
Tall truck / trailer	10 ft	12 ft
RV / fifth wheel	12–14 ft	14–16 ft
Large farm machinery	14–16 ft	16–18 ft

Add space for future growth without overspending

It’s smart to build in a little extra room now instead of getting boxed in later. Add 20–30% to your calculated square footage for circulation, storage growth, and workstations. In many cases, the cheaper move is to add one more length bay – about 10 to 20 feet – instead of making the building wider.

Height decisions matter too. If you’re stuck between two sidewall heights, the taller option often saves headaches later. Just factor in cost: each 2-foot increase in sidewall height adds about $1 to $2 per square foot to the total building cost.

With those three dimensions set, the next step is to line up your door openings and interior layout before you pick the kit.

Plan doors and interior layout before locking in a kit size

After you set the width, length, and height, the next step is to lock in the doors and the floor plan.

Size door openings for the largest vehicle or machine

Start with the biggest thing that needs to go inside. Measure the full height and width, including mirrors, roof units, antennas, and racks. Then size the door opening around that, not just around the base vehicle. For a Class A motorhome, a 14- x 14-foot or 16- x 14-foot opening is a practical place to start.

Door location matters too. End-wall doors are a good fit for drive-through layouts and leave the side walls open for benches and shelving. Side-wall doors can make sense for side entry, but they can eat into usable wall space. If you need to store a trailer or large farm equipment, planning doors at both ends gives you a drive-through bay and removes hard backing maneuvers entirely.

Once the opening size is set, map out how vehicles and people will move through the building.

Sketch parking, storage rows, benches, and travel paths

Before you commit to a footprint, draw the layout to scale. Graph paper works fine. A basic floor plan tool works too. Place parking bays, shelving rows, workbenches, and walkways where you think they should go, then test the flow.

Here’s the simple rule: if you can’t drive in and park like a normal person on the sketch, the building is too small.

Keep the door area clear of turning paths, and make sure traffic lines up cleanly across the floor plan.

Match your layout to Quonset Kits arch models and options

With Quonset-style buildings, the arch shape affects how much side space you can use. The arch is tallest at the center and tighter near the edges, so tall equipment and taller storage should go in the middle. Lower storage fits better along the sides.

Quonset Kits offers P, Q, S, and A arch models with custom width and length, plus options for doors, windows, and insulation. The clear-span interior with no columns gives you full freedom to set up parking bays, storage rows, and work areas based on your plan. Pick the arch model after the door plan and interior layout are set.

Conclusion: Choose a size that fits today’s use and tomorrow’s plans

Start with how you’ll use the building. Then work through your biggest items, site limits, and the key dimensions: width, length, height, and doors. After that, leave some room for what comes next.

A lot of owners say the same thing after the build is done: they wish they had gone 20–30% larger from day one. Height should get extra attention. Adding 4 feet of eave height usually costs about 8–12% more, but it can give you 25–35% more usable storage space.

Once you have those numbers locked in, send your project details to Quonset Kits for a custom quote. Share your intended use, dimensions, door sizes, and site constraints. Quonset Kits will return a custom quote based on your dimensions.

FAQs

How do I size a building if I plan to add equipment later?

Plan for a building 20% to 30% larger than what you need today. That extra room can save you money later, because adding space after the fact usually costs a lot more.

When you map out the layout, count the equipment footprint and add 3 to 5 feet of clearance around it. That space matters for safe movement, routine service, and day-to-day work.

If you might need a vehicle lift or overhead machinery, pick the building height now. It’s much easier to get this right at the start than to fix it later. And if money is tight, go with a design that can be extended in length down the road, while still keeping enough width for your current setup and future workflow.

What if my lot limits the building size I want?

If your lot limits how big you can build, check local zoning and site rules before you lock in your plans. Verify setback distances, maximum footprint, and height limits with your local building department.

If a standard size won’t fit your space, custom sizing may be an option. But in many cases, adjusting your layout to standard increments can cost less. A building specialist can help you sort through those limits.

Should I add height or floor space first?

If you’re storing tall vehicles or making room for equipment like lifts, put height and door clearance first. Most people can picture floor space. Height gets overlooked all the time, and it’s much harder to fix later.

Start by checking the height and door needs for tall equipment, RVs, or lifts. Then build the footprint around those needs.