How to build a 30×40 metal building

Last updated: 15 July 2024

With a 30x40 building kit, you get all the necessary components to construct a precision-engineered, commercial-grade structure in as little as 3-4 days. You can DIY erect the structure or hire a local crew to undertake the construction.

This article provides an overview of the planning, design, and construction process with links to articles for more in-depth coverage.

For details on available kit packages, costs, and prices, see our main 30x40 metal building page.

Step 1: Planning a 30x40 building project

When considering a pre-engineered building for your home, business, or farm, you must be aware of all aspects of the construction process. From planning to execution, we'll guide you through everything you need to know to make your project successful.

Determine Requirements

What will you use your new structure for, and what are your storage requirements? The first step is to complete an inventory of what will be stored in the new structure and ensure it will fit in the 1,200 sq ft.

Decide on a Budget

Take the time to budget for all the components of your build. This will include:

  • The 30x40 kit.
  • Additional accessories (doors, windows, skylights, etc.).
  • A 4" or 6" foundation
  • Permit fees
  • Erection cost
  • Insulation (if required).
  • Interior finishing (if required).

Typical Installed Costs:

  • A basic 30x40 building with no interior finishing will cost $20-$50 per square foot, and
  • a 30x40 metal home with a full interior build-out can cost $100+ per square foot.

See our metal building prices page for a detailed look at pricing and costs.

Decide on a Height

The intended end-use will govern the eave height of your structure. The building height is measured at the eave, and a two-foot clearance must be between the top of the doors and the eave.

Some typical heights include:

  • Garages/shops - 10’ to 18’.
  • Barns - 12’ to 22’.
  • Single-story homes - 10’ to 14’.
  • Two-story homes - 18’ to 26’


Please note: 30 x 40 metal frame buildings are limited to a height of 30 feet.


building dimensions

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Decide on the Number of Framed Openings

The standard 30x40 kit package typically includes one framed opening for a walk door and one for a typical overhead door. You must decide how many more framed openings you need and how big each must be. Remember that each of these will add to the cost of your building because each framed opening requires additional steel.

Also, note that with a 30 x 40 metal building, the center column will typically be placed halfway down the building at 20 feet, giving you two 20-foot wide bays.

Apply for Financing (if required)

Several options are available for financing a new building; see the planning page at the end of this section for more details). If financing is required, identify suitable lenders at this stage. You cannot make the loan application until you have finalized all your building details and are at the pre-construction stage.

Apply for Permits (if required)

You will almost always need a building permit, but some rural and farm properties are exempt. Once you have chosen a suitable building site for your new structure, check with your city or county building department. Note that you won't be able to apply for construction and foundation permits until your chosen kit supplier has received your order and provided you with the relevant engineering drawings.

Our suppliers ensure that your structure is engineered to meet your local codes for wind, snow, and seismic conditions.

See our build process page for more details on planning a construction project, or read this great post on GarageJournal.

Metal building framed openings for doors

TIP: One of the top pieces of customer feedback we hear is 'I wish I'd added more space.' Before ordering your new building, you may also want to consider these similar-sized building kits.

Step 2: Design considerations

The level of design required for your 30x40 building will largely depend on what you intend to use it for. Below, we briefly cover some of the main design aspects you will need to consider when customizing and configuring your new structure.

Decide on a Roof Style & Pitch

The intended end use of your 30x40 building will largely dictate the roof profile. For example:

  • Metal homes can have a gable (traditional), single-slope (modern) monitor, or even a gambrel roof (farm or barndominium), depending on the style you are looking to achieve.
  • Garages and shops will have either a gable or single-slope roof.
  • Barns will typically have a gable, monitor, or gambrel roof style.

Available Roof Pitches:

  • Gable - 1:12 to 4:12 (steeper pitches require special engineering).
  • Single slope (shed roof) - 1:12 or 2:12.
  • Gambrel (Dutch barn) - Upper roof 2:12-3:12 and lower roof 5:12-6:12
  • Monitor - (American barn) - Upper roof: 4:12 - 6:12land lower roof: 3:12 - 5:12

This being said any roof profile and pitch can be applied to your custom 30x40 steel building.

Choose a Floor Plan (if required)

If your new structure will be used as a home, shop house, horse barn, or dog boarding kennel, you must decide on a floor plan that best suits your needs and maximizes floor space. To ensure you have sufficient space:

Step 1: Research available online floor plans and shortlist the ones you think will work best. We also have a selection of sample floor plans to get you started. You can also create basic floor plans with our floor plan maker tool.

Step 2: Complete an inventory of what will be stored in your new structure, taking into account your current and possible future requirements.

Step 3: To understand what will work for your specific setup, plan your layout on graph paper (using a scale of one square = 1 foot) and place/arrange scaled cutouts of your inventory, livestock, and equipment on the floor plan.

There is no need to hire an architect. Our suppliers will advise on design options to ensure you get the building you want in terms of functionality and aesthetics.

3 car garage floor plan

Choose Custom Options

A standard building package is sufficient for most customers, but various customization choices enable YOU to customize and configure the structure to meet YOUR needs. Popular custom options include:

Color options: Mix and match over 20 colors for siding, roofing, and wainscot to get your desired look. See our colors page (follow the link to our design center at the bottom of this section) for sample color schemes and a color visualizer.

Door options: Choose from sectional, roll-up overhead, sliding, or bi-fold doors, and pick sizes, styles, and colors that work for your setup.

Siding options: All kits have pre-painted, 26-gauge PBR metal roofing and siding panels. Alternatively, you can add vinyl, Hardie board, stucco, or faux brick panels.

Structural options: Customize the exterior of your building by adding any number of structural customizations, including roof overhangs, door canopies, or a lean-to.

See our design center for additional details on configuring and customizing a building.

Custom door options

Step 3: Ordering and contracting

Now that you know your building's design and style, let us help you get started. Tell us a little about your project, and we'll match you with FOUR vetted suppliers who will provide competing quotes for your 30x40 kit package. Apply for quotes here.

Once you have confirmed that you are happy with the design, a deposit (20-30%) is required before the factory can manufacture your custom building. A set of construction and foundation plans stamped by an engineer registered in your state will be sent to you (usually in 2-3 weeks).

Most vendors offer a full set of plans, but some charge extra for foundation plans. Before you submit your order, be sure to confirm this with the supplier.

With all the necessary designs in hand, you can now request estimates from a local steel building erection crew (or a general contractor) to construct your 30 x 40 metal building.

You will also be able to:

  • Approach your local building department and begin the permitting process, and
  • talk to lenders (if financing is required).

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Step 4: Pre-construction

The time between ordering your building and taking delivery will typically be around 6-8 weeks, giving you plenty of time to prep your job site. Here are the steps you will need to consider at this project stage.

Site Preparation

Before pouring the concrete foundation, you must prepare the site to be ready for construction. This will include clearing and grading the site. Next, locate and map out access routes for water, gas, and other utilities. It is also essential to verify that the site can support the structure's weight by conducting a soil analysis and determining if excavation and adding road base (or similar) will be necessary.

Run Utilities to the Job Site

Before pouring the foundation, you will bring in plumbers and electricians to bring services to your job site.

Plumbing professionals lay the pipes, which the foundation covers, and the electrician will run a conduit for the power lines to run through the foundation.

If you use your well as your water supply, check that the current pump and pressure tank can handle the additional demand.

Pour the Foundation

A slab-on-grade foundation is typically used when constructing a 30x40 steel building. This foundation provides a stable base for the structure by pouring a concrete slab directly on the graded site.

Foundation and anchor bolt plans are not typically included in the building price, so it is essential to consult with a local, licensed structural engineer to develop a foundation plan that meets all code requirements.


Concrete slab foundation

Unless you have extensive experience installing foundations, we recommend having the foundation poured by professionals. A 4" slab will work for most end uses, but a 6" foundation will be required if heavy machinery is stored or used in your building. Another thing to consider at this stage is in-floor heating, which can be easily added during installation. Lastly, make sure that utilities are also roughed in before the pour.

A 4" slab foundation for a 30x40 metal building will cost $4-$8 per square foot

For more, see our foundations page.

Step 5: Constructing a 30x40 building

When it comes to erecting a steel frame building, you have three main construction options, which we cover below. Follow the link at the end of this section for additional details on the construction process.

Prep for Delivery

Kit packages are typically ready for delivery 4-16 weeks after placing an order. Before starting construction, be sure to have lifting equipment on hand (e.g., a backhoe or forklift) and a place to store the framing, siding, and framing packages at your job site. The final balance of payment is typically due when the kit package is delivered.

Three Options for Construction

DIY Build: You take on the entire project, including pouring the foundation, erecting the structure, and finishing the interior. Steel-framed kits are designed with the DIY enthusiast in mind and come with numbered parts and complete instructions. With some construction experience and plenty of planning, a DIY build can save you 20-30% on the total project cost.

As the foundation is a critical part of the build, we strongly recommend enlisting a professional crew for this build stage.

Self Build: With this option, you act as the GC for the project. You will be responsible for hiring and managing the erection crew, the foundation team, and other subcontractors. You will also need to pull all the required permits. This option will save you the GC fees of 10-20%.

General Contractor Build: You hire a GC to arrange and manage the erection crew and the subcontractors. This is the most costly option, but a good GC brings a wealth of experience to the project and can provide ideas you may not have thought of. This route is also by far the fastest option and one you should consider if you require a short occupancy time.

A GC can also speed up the build time by getting permit approvals quicker due to their knowledge of the process and often due to their existing relationships with the building department and the local inspectors. GCs charge 10-20% of the project cost.

For more details, see our page on metal building construction.

steel frame building installation

Step 6: Finishing a 30x40 building

Your intended use for the building and local climatic conditions will dictate the required interior finishing level.

Wiring Plumbing & Finishing

You only buy the building shell when you buy a kit from one of our suppliers. This includes all steel framing, metal roofing, and siding panels. In addition, you will need to hire local subcontractors to handle the wiring, lighting, heating, plumbing, flooring, and any internal framing that needs to be done.

electrical installation

Add the Insulation

Insulation is a worthwhile investment that can save you money on energy costs year-round. It helps keep your building cooler in the summer and warmer in the winter, prevents condensation, and provides soundproofing. Fiberglass blanket and spray foam insulation are the most popular options for energy efficiency. You can purchase these materials from your kit supplier or source them locally.

For more, see our insulation page.

garage insulation

Interior Framing

Again, this will depend on your intended use for the building. However, if interior rooms or a second level are required, you must hire a local framing company for this project stage.

Most metal-framed buildings are single, wide-open spaces. Optionally, the structure can be split into multiple sections to accommodate an office, a bathroom, a storage area, or a mezzanine loft level.

Walkthrough and Final Inspection

To ensure that your project is completed correctly and per local building codes, formal inspections are essential at various stages throughout construction. A final inspection will be required at completion to complete your permit process. Once you have passed your final inspection, the building inspector will provide you with a certificate of occupancy.

See our page on steel building interiors for additional details.

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