Steve Graham is sinking nearly $100,000 into renovating the back yard of his Olney house, complete with sunroom, new deck, multi-burner stainless steel grill, hot tub, furniture, outdoor lighting, koi pond and landscaping. As a real estate agent with Re/Max selling high-end houses around Montgomery County, he knows he's not alone.

"I'm seeing a lot of people putting a lot of money into their homes -- buying hot tubs, redoing their decks, tearing off decks and building patios," he said, adding that it's not just great for entertaining, it's wonderful for resale. "People will just come in and go, 'Oh, my God, this is so beautiful.' "

But all the money that people are pouring into their back yards is doing more than just pumping up the real estate market; it's virtually creating an entire new industry. Those uber-patios, after all, need the amenities of home: seating, rugs, refrigerators, counters, lighting, heat, music and television, all of which must be impervious to wind, rain, sun and snow. Businesses big and small are rushing to meet this demand, or perhaps stoke it, as is the case with Open Air Designs, a new company based in Bensalem, Pa., that makes weatherproof artwork to hang on the outdoor walls of your outdoor room.

"Right now the demand for it isn't as great as it will be this time next year," said Vice President Jason Kubach. "We're known throughout the outdoor room industry. From September of this year to September of next year, we're spending our current advertising budget on going to the consumer."

The idea of creating living space outside the house began showing up in exclusive shelter magazines about five years ago, but those glossy spreads largely depicted the homes of the wealthy in zones of great weather. But as happened with so many home improvement trends before -- in-ground pools, professional kitchens and home theaters, for example -- what was good enough for the rich very quickly becomes good enough for the masses.

So now, the first thing a visitor sees on Walmart.com is everything needed to create the ultimate outdoor room: patio furniture, fire pit, grill and hot tub. It doesn't matter if you live in Connecticut, either, a state that just got its first store from Australian retail chain Barbeques Galore.

"In the last year I've had a number of instances where we're basically moving into markets I wouldn't have expected," said Michael Lindblad, chief executive of the company, which now has 75 U.S. stores, or roughly double the number five years ago. "The biggest part of our business has been people seeing [built-in barbecue] islands and saying, 'I didn't really think I could do this.' "

Of course, Lindblad has had no trouble convincing people that yes, indeed, they can. He and others say outdoor heaters, in particular, are opening up the market for longer seasons in colder climates.

The outdoor room phenomenon is being analyzed and characterized by a growing number of surveys, most commissioned by the very industries that are gaining tremendous business from the great American backyard build-out. But together, they paint a telling picture of the popularity and scope these projects have taken on.

The Propane Education and Research Council, for example, claims that the number of homeowners with an outdoor living space will double in the next two years. Outdoor spaces, meanwhile, are second only to kitchens as the top renovation projects in people's homes, the report says.

The Hearth, Patio & Barbecue Association (HPBA) says 31 percent of households are considering improving their outdoor grill area, with the most popular steps being a new or better patio or deck, new outdoor furniture and upgraded landscaping. Eight percent of those owners say they plan to add a built-in island for grilling, much like those designed for indoor kitchens with cooktops and counters.

Outdoor furniture maker Laneventure reports that 60 percent of "industry professionals," such as designers, architects and real estate agents, say an outdoor living space adds 10 to 30 percent to the value of a home.

And the Weber-Stephens Products Co., maker of Weber grills, has these facts in its survey: Thirty percent of outdoor room owners use it daily in the spring and summer months and 74 percent of the outdoor room crowd say their "rooms" can comfortably accommodate 10 or more people.

All of this, of course, costs serious money. Though the HPBA says it's possible to start an outdoor room with a relatively modest investment of about $2,000 for a grill, patio furniture and an outdoor heater, the typical expenditure is a lot higher.

"The dealers that we are talking to tell us that is usual for people spend anywhere from $15,000 to $100,000 on the outdoor room," said Donna Myers, a spokeswoman for the trade group.

HPBA's fact sheet on outdoor rooms suggests it's at least a $10 billion business, with Americans spending well over $3 billion on grills and accessories last year, another $3 billion or more on hot tubs and spas and yet another $3 billion on all-season furnishings.

Surveys and magazines generally consider the outdoor room as a defined section of yard or porch equipped with three things: cooking equipment, such as a grill; living and lounging furnishings, and a dining area. But the industry has become much more than the basic amenities; the outdoor room is now being marketed, and bought, as something that should be every bit as comfortable and entertaining as anything one might have indoors.

"Why not expand the entertaining area from the inside of the house to the outside of the house?" said Elizabeth Schultz of Fairfax, whose outdoor room has a grill, a whirlpool, a fire pit, seating for 12, plantings and sconces. She is currently looking for a bar she can add to the mix. She and her husband and their three young sons entertain frequently, she says, for kids and adults.

"People our age and income bracket have done the insides of their houses, so improving the outside in the next natural step," she said. "It's just the natural progression that is certainly spurred on by the prolific production of these catalogues."

Ah, yes, the catalogues. There are numerous home catalogues flooding mailboxes with growing displays of outdoor amenities. General retailers such as Target are selling broad selections of outdoor accessories, and even the Safeway supermarket chain is doing a brisk business selling more full-featured outdoor furniture in its seasonal aisle. And then there are the Web sites: outdoordecor.com, backyardamerica.com, backyardstuff.com and more. Many more.

Weber is no longer just going to sell only grills. Last year the company introduced a gas-powered outdoor fireplace. Executive Vice President Mike Kempster Sr. said Weber is looking to expand into outdoor heaters, lighting and possibly regular cooktops. Furniture manufacturer Laneventure has expanded into outdoor draperies for pergolas and rugs for patios. To top its weatherproof metal "canvases" of landscapes, flowers, golf courses and more, Open Air Designs will soon introduce tiny photovoltaic art lamps that get their power from other light sources. The Propane Council says there's lots more to come, too, including developments in the propane tank itself to make it more user-friendly.

"The industry is developing new lightweight cylinders so that consumers will be able to see the volume of gas inside like in a disposable lighter," said Roy Willis, president of the Propane Education & Research Council. With many of the new backyard amenities powered by propane, the propane cylinder market was up about 20 percent last year, he said.

Those involved in marketing these backyard -- excuse me, home resort -- products say there's a spiral effect going on: As more products are improved and marketed, more people want them and more companies push to create new products to satisfy that growing demand. Now there are home builders offering built-in outdoor fireplaces as options, or even as standard features in some models, said Ross Johnson, business manager for outdoor products for Hearth & Home Technologies, a fireplace manufacturer. Johnson recently completed a presentation to D.R. Horton Inc., one of the country's largest home builders.

"It's the massification of luxury items. People are getting things that before were only for the rich and the famous," Johnson said.

Manufacturing executives say they know there's an aspirational aspect to the outdoor room trend, with less affluent customers emulating the looks they see in high-end catalogues and popular home design and remodeling shows. Retailers, meanwhile, are getting smarter about quickly offering inexpensive but well-designed knockoffs.

Even among neighbors, a trend like this becomes almost contagious. Because the outdoor room is centered on entertaining, it's a joke among high-end grill retailers that when they sell a high-end grill in a neighborhood they haven't served before, they know they will soon sell several more in that same neighborhood.

"I remember, the first time I saw a stainless steel grill I said to myself, 'I gotta have one of those,' " said Barbeques Galore chief executive Lindblad. He likens the almost viral way outdoor rooms have spread to the surge in sales of home theaters a few years ago. They are products that get a ton of exposure every time a new purchaser invites all his friends over to show off the new toy.

The backyard build-outs are getting a boost from another fundamental factor, too. Unlike a home theater, a backyard room can improve property value. After watching their home equity rise dramatically in the past few years, many owners are choosing to take money out of their homes to do renovations, of the houses themselves and the backyard rooms.

"You can easily drop $25,000 into one, but you figure, 'I can get it back in the resale,' " said Dale Ekdahl, managing director of the National Association of Real Estate Appraisers. Because people seem so infatuated with outdoor rooms right now, adding one is an easy way to improve a home's marketability, especially by including a barbecue or fire pit "with a nice laid-in stone foundation," he said.

And that kind of upgrade has a more direct effect on the value of a house, he said, than spending the same $25,000 on something less permanent, such as a home theater or even draperies.

Furthermore, with real estate prices rising so rapidly, some homeowners feel they couldn't move even if they wanted to because they can't afford to buy another house, so they choose instead to spruce up their own places. That's what happened with Graham and his $100,000 outdoor fantasy yard.

"Basically I decided to keep my house because the values are going up so high," he said. "I decided to stay here and make everything the way I wanted it."

Among the products Graham wanted was a $10,000 hot tub made by Cal Spas, a major manufacturer of outdoor spas and, now, high-end barbecue stations, many equipped with televisions and other luxuries.

Cal Spas has found a particular niche in the kind of product that inspires envy, and increasingly designs for the wow factor.

"So now you've got your friends over, and you're all excited, and they're checking out the outdoor kitchen, and then you push a button and this 60-inch screen pops up," said company President Casey Loyd. Indeed, Loyd is not so sure that the power of this moment isn't what's selling some of his television-equipped grills and hot tubs.

Loyd's description of his products and their use suggests something about the backyard industry that few executives want to admit: To a certain degree, a lot of this showy outdoor stuff is just that, for show. But if people want it and it makes them happy, Loyd asks, is that so bad?

"I would have to say I'm hoping they're finding an enjoyable use for it," Loyd said. "If that means enjoying it by watching it, or entertaining their friends with it, or just by playing with it, that's an enjoyable use -- and that's okay with me."

An outdoor room by Frontgate features all-weather wicker and an all-weather rug.Kmart's stainless steel serving cart costs $199.99. At left, a hot tub by Cal Spas. The $9,999 SuperScreen Outdoor Theater System by Frontgate was originally developed for resorts.