Totally mod: a contractor's step-by-step guide to modular housing - Construction Products

Building Products, Sept-Oct, 2003 by Doug Holdridge

Modern modular houses are as good as or better than comparable stick-built homes. Best of all, they save buyers and builders time and money, and can boost builders' profits.

Modular construction, also known as factory-built housing, allows a builder to take advantage of the modular home manufacturer's volume discounts on materials and their accelerated construction schedules. When all the bills are paid, it could cost you 10 percent less to construct a modular house than a comparable stick-framed home.

Besides offering a variety of plans, each manufacturer also provides a range of options for quality fixtures, trim, cabinets, and other features. Many modular companies install products from major manufacturers such as Merillat cabinets, GE appliances, and Andersen and Pella windows. The windows often are higher quality than the low-cost vinyl units found in many stick-built houses in the same price range.

In addition, the controlled environment of a manufacturing facility reduces quality-control problems and makes concerns about bad weather and finding good help a distant memory. Because the factory always is dry, there's no chance that rain-soaked framing members will warp or plywood will swell or delaminate. As a result, you get straighter, better-looking walls and floors.

BUSINESS ADVANTAGES

While material prices for stick builders can vary from one day to the next, modular manufacturers only increase their prices every two to four years. That price stability allows builders to write very accurate estimates. When you send a sec of drawings to a manufacturer, you generally have a firm price within a matter of days. After you enter the costs of site work and finish, you have an accurate cost that isn't subject to unexpected change.

Depending on the manufacturer, the time of year, and the complexity of the plan, the time between placing an order and taking delivery of the completed house is as little as two weeks to as long as several months. But typically it's less than the time it would take you to erect a stick-built unit.

Besides the advantages of shorter build schedules and the benefits of building in a controlled environment, the systems have other benefits. You no longer have to deal with framing, roofing, insulation, or drywall subs because all that work is done by the manufacturer. And you don't have to spend hours researching materials invoices to make sure they're accurate. Meanwhile, you have fewer phone calls to make, fewer 1099 forms to prepare, and fewer insurance certificates to collect for the annual insurance audit. All this translates into much less administrative time.

Plus, you also can enjoy reduced insurance costs because the projects are completed much faster. Waste-removal costs are minimal and the homeowner pays less interest while waiting for the house to be finished.

DESIGN OPTIONS

Each modular manufacturer has a portfolio of stock plans and many buyers are happy to choose a model directly out of a catalog. But manufacturers know they have to give buyers what they want. If the customer provides a print or a floor plan, a flexible modular manufacturer can redesign it as a modular. There also are architects who specialize in custom modular designs.

The main design limitation has to do with moving a module to its site. If the module is 13 1/2 feet wide or so, transport isn't a problem. State laws vary, but once you get up to 16 feet in width, you usually need a state police escort in front and back as the module travels to the site--and that gets expensive.

Accuracy is extremely important when it comes to the foundation. You can fudge a stick-built house if the foundation is a little off, but that's harder to do with a modular. When you set the modules down, you want to be sure they're going to fit.

Modules arrive on steel carriers towed by tractor-trailer rigs and are met by a four-or five-person set crew and local crane and operator. The manufacturer can provide its own crew, but you can hire the same setting sub every time.

The back module usually goes on first. It's strapped for the lift, craned off the carrier, and then carefully set down on the foundation. The set crew places support posts under the central girder and erects the rear half of the fold-down roof trusses. The front section of the roof is raised before the front module is strapped and eased into place. This leaves a gap at the ridge, which is closed off with piggyback trusses that are craned onto the roof along with the necessary OSB sheathing and shingles. The whole process, from the arrival of the truck to closing off the roof, takes about half a day.

Factory-made garages are available, but they may hOC be cost-effective. Compared with a house module, which is braced by interior partitions and a rigid floor assembly, a garage is basically a big flexible box with no bottom. The factory has to add a lot of expensive temporary bracing to stiffen it for transport, which offsets the cost savings of modular construction. You can eliminate that added expense by having the set crew stick-build garages.