Most modular home designs are one, two, or three modules deep and one or two modules high. A few companies build homes three modules high, although they require special approvals from the customer’s state to ensure they comply with the building code. Most homes are two modules wide, with typical widths of approximately 24 feet, 26 feet, 27 feet 6 inches, and 31 feet 6 inches. Three module wide homes typically range from 36’ to 47’ 3”. The usual practice is to place modules side by side, with the long sides parallel to the road. Some designs, especially when built on narrow lots, turn the modules perpendicular to the road. Modules can also be turned perpendicular to each other to create T-, L-, or H-shaped houses, which is one of many techniques the modular industry has employed to shed its image of making boring boxes.
Modular Home Designs – Minimum Size
Modular manufacturers will build homes only if they can sell them for a competitive price and still make a profit. The minimum order they will take is a function of the amount of labor and materials required to build the home. Too little labor and materials will make a home uneconomical to build at the factory. This means that small additions usually will not work financially, and neither will larger additions that are essentially empty boxes. For example, a 16 foot by 27’6” foot great room addition is usually too small and devoid of value-added work to make economic sense. On the other hand, a 24-foot by 24-foot in-law addition with a kitchen and bathroom can work nicely.
Modular Home Designs – Adding Length
Adding length to a modular home is always easy to do from the manufacturer’s point of view, as long as it stays within the maximum production and delivery dimensions. This is also true about adding bump-outs to the end of a module, such as a walkout bay. Making a plan of a given size bigger by adding to the length of the modules is one of the best values in the entire construction industry.
Modular Home Designs – Adding Width
Increasing the size of a particular plan by widening the modules is also a very good bargain. The cost per square foot is often a little more for adding width than length, because the floor system sometimes needs to be beefed up; for example, from 2 x 8 floor joists for a 24-foot-wide home to 2 x 10s for a home with a width of 27 feet 6 inches. Widening a module, like lengthening a home, will always add more equity to a home than it costs.
Modular Home Designs – Adding a Bumpout
Adding a “bump-out”, such as the walk-out bay, to a long wall on a module that is already at its maximum width is more involved than adding one to the end of a module. The manufacturer must either build the bump-out as a separate miniature module or ship the necessary materials to the general contractor.
Modular Home Designs – Using a Saddle or Cricket
Attaching one or more additional modules perpendicular to the long side, as discussed above can also enlarge a standard plan. This will require that a “saddle” or “cricket” be built to join the roofs.
Modular Home Designs – Adding a Second Living Unit
Another way to enlarge a home is to attach a separate living unit to the home, such as you might do to create an in-law addition or a two-family unit. The second unit can be designed with either a custom or standard plan.
Modular Home Designs – Additional Delivery Fees
When enlarging a given plan, make sure that any additional delivery fees are included in writing. Increasing the width up to 27 feet 6 inches should incur a relatively small fee. The fee for widening a home to 31 feet 6 inches, however, will be more substantial. Adding length to a home will sometimes require additional delivery carriers, which also can add significantly to the cost. This will happen when the original length of the house calls for delivering two modules on one carrier but the new, longer plan requires delivering the two modules on two carriers. Consequently, the new design will require an additional carrier for each pair of modules. For example, if a manufacturer’s maximum length for shipping two modules on a carrier is 30 feet per module, it can deliver a two-module-wide 28-foot-long in-law apartment on one carrier. However, if the apartment is lengthened by 4 feet, making each module 32-feet long, an additional carrier will be needed. When the original plan is a 28-foot-long two-story that is being lengthened to 32 feet, two additional carriers will be needed.
Additional carriers will also be required whenever lengthening a home makes the modules too long for the manufacturer and general contractor to deliver to a site. For example, a narrow road to the site may make it impossible to for a longer carrier to negotiate the turns. The only solution, other than keeping the home at its original length, might be to have the manufacturer divide each longer module into two shorter modules. The manufacturer will charge more to do this, but it may be the best way to get the home you want.
Modular Home Designs – Additional Option Costs
Enlarging a home will also increase the cost of any options that are affected by the increase. For example, upgrading to a premium siding will cost more when a home is made wider or longer, since more area needs to be covered. Other optional features will only increase in price if a particular room increases in size. For example, a dining room wood floor will only cost more when a home is lengthened if some of the additional length is put into that room. Increasing the size of a particular room can also force you to add windows or doors to meet the building code, which requires a minimum amount of “light and vent” for each room.
For more information about modular home designs, see Designing a Modular Home and Modular Home Specifications and Features in my book The Modular Home.