The doors on display in Scott Thurber's California showroom are huge: 25-by-9-foot slabs of glass, low-silled and minimally detailed. "People walk in and they're just blown away," reports Thurber, general manager of Associated Building Supply in Oxnard, Calif. "They say: 'That's what I've been looking for."' Customers and contractors alike are loving big glass doors for a big reason: They help create the illusion of space in today's smaller homes by providing a seamless transition to outdoor living areas–areas that can be created at far lower costs per square foot than what's inside the home. While the cost of the giant panels of glass keeps most systems in the higher-end markets, interest has spread nationwide and is drifting down to the design details in average patio doors, which will see double-digit growth through 2012 and 2013, reports Window & Door magazine. This early in the game, the competition is tame relative to windows, Thurber says, so for him, big doors mean big margins.

"I spoke with a couple of architects this morning down in the South where their outdoor living spaces are as big as the house," says Mark Fanelli, vice president and general manager of Royal Window and Door Profiles. And at 20% the cost of conditioned space, moving outdoors is a good move in a bad economy, climate permitting. In May, the company launched the Opus Patio Door Series with a Super Quiet roller to make the transition easier, creating a 16-foot expanse of glass in the four-panel sliding door configuration. Multiplying the panels of a traditional patio door is only one way door designers bridge the demand for larger spans. There are several systems engineered to hold, move, and store massive panes of glass. Lift-and-slide doors have a large handle that lifts heavy panels like a jack so they push open with a finger, such as the Ultra Series TerraSpan Lift & Slide Doors by Kolbe & Kolbe Millwork Co.; Marvin's Clad Ultimate Lift and Slide Door; and the Premium Series 1000 Sliding Patio Door by Ply Gem Windows, which requires just 8 pounds of force to roll open a 550-pound panel, the maker claims.

Backed by substantial weight, these types of doors seal weather-tight when shut.Brown Beige Striped Curtains Other systems hang from a track. Digital Camera Child ModeJeld-Wen's Custom Fiberglass folding door system and the Bi-Folding doors by Panda Windows & Doors can be nearly limitless in length, while NanaWall Systems' Single-Track sliding doors are good for multi-angled walls because they track around obstructions. White Wall Tire ShaverSolar Innovations' new SI30000 Monster Wall System accommodates doors that fold, stack, or slide, and its dual-wheel trolleys can hold 4-by-12-foot or larger panels. "You can have your traditional slider, but that's 60-year-old technology," says Matt Thomas, director of marketing for NanaWall Systems.

"In a typical two-panel slider, you only use half the opening. It creates a whole different emotional component when the entire wall opens up, because then you have connectedness." Doors with the latest technology fold accordion-style or hide inside the wall like a pocket door so the outdoor room integrates with the indoor space seamlessly. Typically, these configurations include an access panel that swings open independently so users don't have to push back the entire wall to let the cat out. "Gone are the McMansions," says builder Stephanie Denton of Denton Homes in Waukee, Iowa. "We're seeing people want more flexible space; if you make a multi-purpose room and add a folding glass door you can make that room larger if you need it." Custom builder Mike McDonald of Oakland, Calif., calculates that shaving 1,800 square feet from a 4,500-square-foot floorplan and then adding it back outside could make the home feel as large but cost much less. Still, for the average house, large transitions don't come cheap.

"When you create a big open void, you're going to have challenges and cost associated with it," McDonald says. The opening itself is a cost, as is the door, the installation, the engineering involved and, when required, the steel supports. "But that said, from a design perspective it's no more costly to put in a big opening system than it is to put in six panels," he maintains. For homeowners who can't afford Weiland Sliding Doors & Windows' 16-foot-tall liftslide, there are other ways to open up the view for less: sidelites and transoms, low sills, thinner stiles, and details down to how the drywall meets the door. The 5-1/2-inch stiles and rails are getting narrower and more contemporary on French doors as well as sliding patio doors, Thurber observes. He also sees more drywall returns, where the wallboard butts the window in place of trim. "People are probably tired of the old ogee-lug look where you've got a lot of different steps and millwork, heavy casings, shadow lines, and detail on the inside," a change he attributes to a growing desire for an uncluttered view.

Narrow stiles in Therma-Tru's vented sidelites, new to its Smooth-Star and Fiber-Classic Oak Collection patio doors, let in more light. The new vinyl Tuscany Series swinging doors by Milgard Windows & Doors are traditionally hinged but feature more than 30 single- and multi-panel configurations with fixed or operable sidelites. Simonton recently added a 10-foot-wide, two-lite vinyl patio door to its Impressions line for the western U.S. market and plans to go bigger. "We are seeing a continuing trend of homeowners in all regions of the country wanting to bring more of the outdoors into the home through large window-wall configurations, featuring combinations of patio doors," says Christopher Burk, product manager for Simonton Windows.The sliding glass door traces its ancestry to the Japanese “Shoji” and “Fusuma” sliding panels. While these panels are traditionally interior pieces, the Western sliding glass door is an exterior piece also called a “patio door”, for the patio they usually open onto.

These doors are made of glass and allow a great amount of natural daylight in. Once an architectural luxury, the post-war building boom saw them installed in many homes, usually ranch-style houses.Early sliding glass doors looked great, but they were a source of energy loss and a weak point for security. Modern sliding glass doors look even better, are stronger, and much better insulated.A basic sliding glass door by itself costs around $300.00. This is the classic door that most people think of, which is a 6-foot pair of plain glass panels that sit inside of a clean, simple frame. An 8-foot door usually runs from $700.00 to $1,000.00.Some doors are available pre-hung. This is an entire unit that basically only needs a hole in the wall to be put into. These tend to cost $1.000.00 to $4,000.00 or more depending on features such as screens, blinds, triple-pane glass, or a grid that imitates French doors.Impact-resistant glass is designed to withstand hurricane-force winds. However, this added bit of security can double the cost of the doors.

The price ultimately depends on the manufacturer and what their models offer. For example:The length of the warranty varies by manufacturer, specific product, and/or components of the door. Typical warranties vary between 10 and 20 years. Check with whomever issues the warranty to see if modifications, such as glass tinting, voids the warranty.Sliding glass doors require a large hole in your wall. If you are installing a new sliding glass door, local codes most likely require a permit and a contractor. It constitutes a major alteration to a load-bearing wall (all exterior walls are load-bearing) and can affect the structural integrity of your house. Get 3 to 5 quotes from licensed contractors who have experience in making wall alterations.Removing the old door is a moderately involved process that usually requires a helper. Remove the interior trim first, then lift the movable pane out. Next, remove the trim and anything holding the stationary panel in. Once the panels are removed, remove the exterior trim, the jamb, and then the frame.

Finally, clean the opening out of any old screws, nails, or other debris left behind.Pre-hung doors install relatively easily, usually taking about a day. This doesn’t count the clean-up work like repairing the exterior and interior wall areas. This is considered a moderate DIY job. Custom hung doors, however, usually require altering the supports in the walls. This should be done only by a professional with experience in altering load-bearing walls. The location of interior components such as vents may prevent you from placing the door where you want, and electrical wiring should always be altered, moved, or handled by a professional.Locks have long been the weak point of sliding glass doors. Any burglar wishing to avoid the noise of broken glass could simply jiggle the door strongly enough and get it open. Modern locks for sliding glass doors are much more secure, and auxiliary locks can be purchased for added security when you are away.A basic lock for a sliding glass door costs around $10.00, but other options are available for between $20.00 and $40.00.

These locks include foot locks, deadbolts that install at floor level, and telescoping security bars.Screen doors for patio doors come in two types: sliding and retractable. Sliding screen doors cost about $125.00. Retractable doors work like sideways venetian blinds and cost around $330.00.Replacing a sliding glass door can be done DIY, but the doors are heavy. You will need an extra set of strong hands. Also, a truck will be needed to deliver the doors to your home, and they won’t fit in the family car. If you don’t have a truck of your own that can haul the doors, you will have to pay for delivery. Finally, whether DIY or professionally done, the job should be done during fair weather. You will have a large hole in your wall for at least a day, and you don’t want cold air, rain, or other discomforts getting in. Starting early in the morning will give you the most time and the best chance of getting the job done in one day.As a side note, keep your children and pets away from the work area.

If glass gets dropped, they can get injured on broken glass.To keep your patio door opening, closing, and locking well, some basic maintenance is needed. Fortunately, most of this is easily accomplished with a screwdriver, a rag, and maybe some nylon shims.Keep the tracks clean of debris and build-up. When you vacuum, use the window track attachment to vacuum the track for your door. This is easiest way to keep it clean. During wet weather it can become clogged with whatever gets tracked in off of your feet. All you need for this is a rag, some cleanser, and a little elbow grease.If your door is starting to drag, add a little lubrication to the track. If this doesn’t do the trick, check the rollers on the top and bottom. They could be wearing down. The good news is that these are easily removed and replaced. If the rollers haven’t worn down, they may just need adjusting. An adjusting screw is usually found toward the bottom and top of the door.Like rollers, locks also can get out of adjustment or need lubrication.