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How Are Module Homes Built?

Concept of construction. 3d render of house in building process

Unlike site-built homes, modular homes are built in a factory setting, shipped in pieces to a location, and assembled on a foundation. This process decreases construction time, provides a weather-controlled environment for the materials and building, and allows you to customize your home. But, how exactly does this process work? And what are you responsible for?

Preparation Period

The preparation period is where the bulk of your responsibilities take place. Before your home can be ordered, you will need to find a location to place the home and obtain any necessary permits. Once your deposit is submitted on the home you’ve chosen, factory construction begins. While your home is being built, you will make preparations for the foundation to be built, utilities installed, and your home to be delivered.

It’s very important that you follow the site requirements closely so your home construction can move forward as seamlessly as possible. Your general contractor and home seller should walk you through this process.


Once your deposit is received and your dealer/builder has received the building permit information, your home will begin being built in the factory. The time to build a modular home takes about 4 to 6 weeks from the day your home is ordered, but could vary depending on additional features, bad weather (for traveling purposes,), etc. But before delivery, each module is meticulously crafted in the factory.

Stage 1: Floors

Floor systems are the modular home’s foundation. All other parts of the home are dependent upon a well-built floor. Floors are built at the same time as wall and roof systems. Floors are constructed on what is termed jigs; these are the width and length templates on which the floors are assembled. The jig ensures that the wood members conform to the standard floor widths, allowing floor widths to be exact and within pre-established measurement tolerances.

Stage 2: Walls

Walls are like the skeleton of a home. They support the home’s roof system and dictate its floor plan. Again, wall fabrication transpires simultaneously as the floors are built. Most fabricators use 2” x 6” studs for exterior walls and 2” x 4” studs for interior walls, with all stud members laid out in increments of 16” on the center standard before being nailed in place. Drywall is adhered to the studs by a special foam seal adhesive, allowing for a smooth flawless drywall finish with fewer nail pops.

Exterior walls are then lifted by crane over to the floor section where they are carefully set into place. It is important to note that walls are fastened directly to the floor system, perpendicularly, as prescribed by a nailing schedule to ensure a very sturdy, tightly built structure. Interior walls are then lifted to the floor system and secured in the same manner.

Stage 3: Roof/Ceiling Systems

Engineered with a fold-up, self-supporting rafter system, the modular roof system is one of the more complicated stages of the modular home construction process.

For easy installation, roofs are built adjacent to the floor and wall stations at sub-assembly stations; these stations are where various home components are built and then delivered to and installed in or on the house, saving time because they reduce the amount of construction done on the line.

Stage 4: Plumbing & Electrical

While in the production facility, water supply lines, and waste lines are installed in the kitchen and bathroom areas. Next, modular homes are fully pre-wired in the production facility as prescribed by the NEC (National Electrical Code) and the home’s electrical plan. 110- or 220-volt wiring is used and “pulled” through the roof system, then through drilled holes in the wall cavities into areas of the home where electrical service is needed.

Stage 5: Exterior Doors & Windows

Installing the exterior house wrap and exterior doors and windows takes some preparation and doing it correctly guards against air and water infiltration. First, a Tyvek® polypropylene air infiltration barrier or house wrap is installed around the entire exterior of the unit. Then, flashing is installed around the perimeter of all exterior Therma-Tru® doors and Andersen windows, protecting the home against any water intrusion. Windows are leveled, glued, and fastened into place. Doors openings are prepared, and the door sill, threshold, and flashing are installed. Caulk is applied around the openings, and the door units are installed, set, and adjusted.

Stage 6: Siding & Roof

 Measurements are taken, and a plumb line is drawn to ensure that all successive courses of siding are level. Each course snaps into place and is affixed with a nailing flange. Finally, the roof is completed. 7/16” OSB sheathing is nailed into place. Next, drip edging is attached, an ice and water shield is installed around all eaves, synthetic felt paper is installed over the entire roof, and shingles are installed.

Wrap And Load

With production complete, attention is turned to protecting the modular units in transportation to the job site, where final assembly will take place. The units are readied with a weather-resistant membrane stretched around the entire unit structure to protect against elements during travel.