When Jeld-Wen sales manager Brent Adair retrofitted his San Diego home with one of his company's long-span folding door systems last year, he expected it to be an oddball job. The product, which the company introduced a year ago, wasn't conceived with existing homes in mind. But that hasn't stopped remodelers from using it. “When we initially came out with this system I thought it would be used only in new construction,” Adair recalls. “As it turns out, half of our jobs have ended up being retrofits.”
But although remodelers have warmed to these products, everyone we talked with for this article agreed that a retrofit can pose a real challenge. Door companies and installers alike said that any skilled contractor can install one of these systems, but that the job demands more care than the installation of conventional doors and windows. Part of the challenge comes from the need to assemble the various components on site, while another part of it comes from the framing requirements, which are more stringent than for nearly any other glazing system.
UNDERSTANDING THE PRODUCTSLong-span door systems can create a clear-span wall opening up to 24 feet long and 10 feet high. Homeowners have always had the option of having either a wall of glass or a long opening uninterrupted by posts, but until three years ago someone who wanted both had to choose between two niche companies. Now, they can choose from a growing list of big-name door- and window-makers (see source list on page S-108).
The increasing popularity of outdoor living has created a healthy demand for long-span door systems, which let homeowners create continuity between indoor and outdoor spaces. Although these products were conceived with new construction in mind, many of them have been finding their way into retrofits.
The appeal of these systems should come as no surprise. As demand for outdoor living spaces continues to grow, especially in mild climates, so does the market for large openings. Long-span systems are the pinnacle of this trend, in that they meld inside and outside into one continuous space. The system that Adair installed in his home was a relatively small one — 12 feet long with four folding panels — but it has changed the way he uses his living area. “When the doors are open, they literally are able to double the size of my living area because the inside flows out to the back. It's more of a wall that opens, than a set of doors.”
These products aren't for the budget-conscious. The manufacturers interviewed for this article gave an average price range of $800 to $1,200 per running foot for a dual-glazed, 8-foot-tall system with pine frames painted in stock colors. Lead times tend to be about six weeks. Taller panels, different wood species, or better glazing will raise the price and increase the lead time. So will a retrofit that requires custom-sized panels.
These systems are available in folding and sliding varieties. Folding systems hang from a single track attached to the structural header. They typically consist of two banks of door panels that open to the left and right. When closed, they present a flat surface; when opened, the panels fold against one another, accordion-style, and stack flat against either end of the opening. Some manufacturers offer an “everyday door” option in which one of the doors at the center of the opening is hinged to the door next to it in such a way that it can be opened and closed like a standard hinged door, for everyday use.
In a sliding system — also known as telescoping or multi-slide — each door has a set of bottom rollers that ride on a metal track. Because each door in a sliding system travels in its own plane, the more doors there are, the wider the track must be. For instance, an eight-panel system will have four doors on each side, requiring a track more than 10 inches wide. When closed, the doors in a sliding system “step” from the ends of the opening to the center, with the end doors being closest to the home's exterior.
Although doors sit snug against the track when closed, pulling on the door handle lifts the first door up, making it easy to slide. As the doors are pulled open, a coupler on each door grabs and lifts the next door. When fully open, the doors stack up parallel to one another at either end of the opening. The contractor also has the option of creating pockets at either end of the opening, into which the doors disappear. In these cases, the last panel can be fitted with a follower skirt — usually a piece of wood matching that used for the doors — that closes off the pocket.
One feature you can get with a sliding system that you can't with folding doors is a motorized belt drive that will quietly open and close the doors at the touch of a button. As an example, Vista Pointe Architectural Systems' co-owner and vice president of operations Dave Stevenson says that his company's motor accessory consists of a steel-impregnated, toothed rubber belt that runs in the track above the door panels, and that's attached to a pulley on one end and a motor assembly on the other. To accommodate the motor, the framer needs to add an extra 10 inches of length to the pocket beyond the depth needed for the panels. The cost is about $4,000, regardless of system size. Stevenson insists that the doors are easy enough to operate without a belt drive, and doesn't recommend it unless the panels are very large or the homeowner has strength problems or a physical disability.
As for weather resistance, some contractors recommend always placing these doors under a substantial roof overhang. Manufacturers say that's not necessary but add that not all door systems perform equally when subjected to water. A folding system with a weather-stripped, stepped sill will have the best performance, but many sliding systems are just as tight. For instance, Dave Koester, a brand manager at Weather Shield, says that his company's telescoping door has a design pressure rating of 50, which means that it won't leak when subjected to windblown rain that hits the door with a pressure of 50 pounds per square foot. That's good enough to meet code in most coastal areas.
Note that sliders can have different types of tracks, so it's important to get the right type. One, which is most popular in the Southwest, is nearly flush with the finish floor. It does a good job at dust and air control, but no one boasts of its ability to stop windblown water.
FRAMING IS CRITICALIf you take away just one piece of information from this article, make it this: In a long-span door installation, the quality of the framing is absolutely critical. The top track of a bifold or the bottom track of a sliding system must be level to within 1/8 inch per 12 feet of length, and it has to stay that way for the life of the door. Adair says that while it probably won't take any unusual framing to get this stiffness on a 12-foot opening in an existing wall, wider openings must be engineered. That makes them more appropriate for an addition or new home. “It's unlikely that someone would put an 8- or 24-foot-wide system into a retrofit,” he says.
“People who have been in business for a long time understand that plumb and level is important,” Stevenson says. “The difference with these systems is that the opening has to stay that way over time.” Top-hung systems are more sensitive to frame movement. In a slider, the panel extends halfway into a 1½-inch-deep track, leaving ¾ inch of play. He says that there isn't such play in a bifold, and that it can start to bind after ¼ inch of sag.
Door manufacturers say that an LVL beam should be fine for a 12-foot opening, but for longer spans they recommend a steel I-beam with a wood buck attached to the bottom flange. “We seldom see built-up beams,” says Jon Sawatzky, an architectural consultant with Loewen. “Many engineers have concerns because of deflection and warpage with SPF lumber.” In a sliding system with a 10- or 12-inch-wide track, some contractors install two headers side by side. In this case, manufacturers recommend spanning the width with 1-inch plywood. It adds rigidity, and provides a continuous, solid anchor for screws.
Some sliding doors are better at keeping out water than others. The bottom sweep of the FlushTrak door (top right) is good at dust and air control; don't depend on it to keep out windblown water. It's most popular in the Southwest. Vista Pointe's WeatherTrak system (below right) prevents water infiltration with a blade at the base of each door panel that fits into a channel in the track. Weep holes in each channel prevent water buildup.
Some contractors will set the header higher than necessary, and place shims between it and the door system's upper track. That way, the shims can be adjusted if there is settling. For minor settling, most door systems have adjustments built into framework so you can re-square or re-shim. “Our [sliding] doors have shims that you can adjust with a screwdriver from inside the home,” says Kolbe & Kolbe Millwork's product manager Lance Premeau.
To avoid problems in a new home or addition, experienced installers warn against installing the door system before the roof and drywall are in place. Chris Brown of Exclusive Windows and Doors in Austin, Texas, has installed 20 of these systems, in openings as long as 24 feet. The only callback he has ever had was for a sliding system on the bottom of a three-story home. “It was working perfectly when we installed it, but as the workers loaded up the house it settled, and it started to pinch the door panels between the top and bottom of the frame. We had to uninstall the top jamb, then re-shim and re-install it.”
INSTALLATION ISSUESAs for the door system itself, some dealers have certified installers, some don't. Most manufacturers insist that an experienced contractor and a helper should have no problem installing either type of system in a day the first time they do it, if they follow the manufacturer's instructions and take advantage of the manufacturer's technical support, where available. With folding doors, the installer preassembles the frame, then slides it into the rough opening, shimming where necessary to get the top track plumb and level. With a sliding system, the installer assembles the track pieces in place in the opening. Once they have a few installations under their belts, they should be able to complete one in about four hours.
Brown has had no quality problems with any of the doors his company has installed. “These units are so well engineered and the hardware works so effectively that, if installed properly, you don't have any problems,” Brown says. “But some of the details have to be right on the money,” for example, making sure that everything is installed square and level. Another is making sure that the installer follows the fastening schedule. “The folding door system hangs from the top rail and is subjected to a lot of torque when the doors are opened,” Brown says. “It has to be secured rock-solid.”
In other words, the same can be said for installing these doors as for framing the opening they will go into. It doesn't require any new skills on the part of the contractor, but it may take more care than they are used to exercising.
—Charlie Wardell is a freelance writer in Vineyard Haven, Mass.