Modular homes are made from the same core materials as site-built homes. As of, the key difference is one of construction method: builders assemble the home in factory-made sections, called modules, and transport those sections to the building site. Most modular homes use wood or engineered-wood framing, concrete foundations, insulation, drywall, roofing, siding, windows, plumbing and electrical systems.
Modular Home Materials at a Glance
| Home component | Common materials |
|---|---|
| Structural frame | Dimensional lumber, engineered wood, laminated veneer lumber, wood I-joists or, in some designs, light-gauge steel |
| Exterior walls | Wood studs, OSB or other structural sheathing, house wrap, insulation and exterior siding |
| Interior walls | Wood or metal studs, drywall and paint |
| Floors | Wood joists or I-joists, OSB or plywood subflooring and finished flooring |
| Roof | Wood trusses or rafters, OSB roof decking, underlayment, asphalt shingles or metal roofing |
| Foundation | Concrete slab, crawl-space foundation, basement or piers, depending on the design and site |
| Insulation | Fiberglass, cellulose, spray foam, rigid foam, mineral wool or structural insulated panels |
| Plumbing | PEX, copper or other code-approved piping |
| Electrical system | Copper wiring, electrical panels, outlets, switches and light fixtures |
| Exterior finishes | Vinyl siding, fiber-cement siding, wood siding, brick veneer, stone veneer or stucco |
| Interior finishes | Drywall, cabinets, countertops, tile, carpet, hardwood, vinyl or laminate flooring |
What Is the Frame of a Modular Home Made From?
Most residential modular homes use wood framing. Common materials include dimensional lumber, engineered lumber, laminated veneer lumber and wood I-joists. These materials form the wall studs, floor joists, roof trusses, beams and other structural components.
Some modular buildings use steel framing, concrete systems or composite materials. Modular construction does not require one specific framing material. The choice depends on the design, structural loads, transportation requirements, climate and applicable building code.
What Are Modular Home Walls Made Of?
A typical modular exterior wall may contain these layers:
- Interior paint or wall finish
- Drywall
- Stud framing and wiring space
- Insulation
- OSB or plywood structural sheathing
- Weather-resistant house wrap
- Exterior siding, brick veneer, stone veneer or another cladding
The exact wall assembly varies by manufacturer and climate. Some factory-built walls use dense-packed cellulose, rigid foam, continuous exterior insulation or structural insulated panels.
A structural insulated panel, or SIP, usually has a foam insulation core between two sheets of OSB or another structural facing material. SIPs can be used in walls, roofs and floors.
What Are Modular Home Floors and Roofs Made Of?
Modular home floors commonly use wood joists or engineered I-joists covered with plywood or OSB subflooring. Finished flooring may include hardwood, tile, carpet, vinyl or laminate.
Modular home roofs commonly use wood rafters or roof trusses, OSB roof decking, underlayment and asphalt shingles. Some homes use standing-seam metal roofing, architectural shingles or other approved roofing products.
The roof may be partly completed in the factory and finished after the modules are joined at the site. The installation process depends on the design, transportation method and manufacturer.
What Type of Insulation Is Used in Modular Homes?
Modular homes can use:
- Fiberglass batts
- Blown-in cellulose
- Spray polyurethane foam
- Rigid foam boards
- Mineral wool
- Structural insulated panels
Insulation may be installed in the walls, floors, ceilings or roof assemblies. The required amount depends on the local energy code and climate zone. A home built for a cold climate may need more insulation and air sealing than a home built for a warm climate.
Are Modular Homes Made With Concrete?
Yes. Concrete is commonly used for the foundation, including slabs, crawl-space walls, basement walls and footings. It may also be used for steps, porches, garages and other parts of the project that are built at the site.
The factory-built modules themselves are often wood-framed, although concrete, steel and other structural systems are possible. The foundation is usually prepared before the modules arrive.
Do Modular Homes Have Plumbing and Electrical Systems?
Yes. Many plumbing, electrical and heating components are installed inside the modules at the factory. These may include:
- Water supply lines
- Drain and waste pipes
- Electrical wiring
- Electrical panels
- Heating and cooling ductwork
- Light fixtures
- Plumbing fixtures
- Kitchen and bathroom components
After delivery, contractors connect the systems between modules and connect the home to local water, sewer, gas and electrical services. The National Association of Home Builders states that modular sections can arrive with walls, floors, ceilings, wiring, plumbing and interior fixtures already installed.
Are Modular Homes Made With Cheaper Materials?
Not necessarily. Modular construction describes how a home is built, not the grade of its materials. A modular home may use builder-grade, premium or custom materials, just like a site-built home.
Material quality depends on the construction specification. One modular home may have vinyl siding, fiberglass insulation and laminate flooring. Another may include fiber-cement siding, spray foam insulation, hardwood flooring and custom cabinetry.
Ask the builder for a written specification that covers:
- Wall and roof insulation type and thickness
- Framing size and spacing
- Sheathing type
- Window performance ratings
- Roofing and siding products
- HVAC equipment
- Plumbing pipe materials
- Cabinet and countertop materials
- Flooring and finish allowances
- Work completed at the factory
- Work that remains at the site
How Are Modular Homes Different From Manufactured Homes?
| Feature | Modular home | Manufactured home |
|---|---|---|
| Building standard | State and local building codes | Federal HUD Manufactured Home Construction and Safety Standards |
| Foundation | Typically installed on a permanent foundation | May use an approved foundation system |
| Permanent chassis | Usually no permanent chassis | Built on a permanent chassis |
| Construction method | Built in factory-made sections | Built in factory-made sections |
| Legal treatment | Generally treated like site-built housing | Subject to manufactured-housing rules |
HUD states that modular homes are built in factory sections to meet state, local or regional building codes. Manufactured homes are built to the federal HUD Code and constructed on a permanent chassis.
What Should You Check Before Buying a Modular Home?
The material list alone does not tell you whether a modular home meets your needs. Compare the written specifications for framing, insulation, windows, roofing, siding, plumbing, electrical work and interior finishes. Also confirm which parts of the project the factory completes and which parts the site contractor completes.