You've heard it a zillion times: When it comes to houses, they don't build 'em the way they used to.

Sometimes that's a good thing, and sometimes it's not.

Think about Grandmother's house--the mythical over-the-river-and-through-the-woods one, not the condo on the golf course in Boca. That home was as strong as the bricks it was built with, held up not only by love but also by solid wood floors and sturdy plaster walls. It was all carefully put together by craftsmen who labored over each small detail of the elaborate wood trim.

Of course, the place was drafty, the cellar was damp, and every time you turned on an appliance in the tiny kitchen the lights flickered all over the house.

Is that house better than one built today? Well, yes and no. Since Grandmom's house was built, much about home construction has changed. Technology has improved houses in numerous ways, particularly in terms of energy efficiency. At the same time, cost pressures often have led to what many perceive to be lower-quality construction. And sometimes, new materials that were supposed to be big improvements have turned into disasters.

Bill Dupont, an architect who works for the National Trust for Historic Preservation in Washington, has a telling perspective on old construction. "I suppose there were some poorly built houses at any time in history," he said. "But the things that tend to survive tend to be the ones that were better built."

"A new house that's built custom has many similarities to what we consider the good qualities of older houses," said Stephen Vanze of Barnes Vanze Architects in the District.

But for many people, he said, "Houses have become more of a commodity than they used to be. People buy them more like they would buy an appliance."

The skeleton of most houses is the same as it has been for a century: wood frame, usually erected on-site. But the wood is different, largely because we have used up the stuff from ancient forests and now rely on tree-farm wood and the products made from it, such as particle board and engineered beams. Sometimes that's better, sometimes it's not.

Good: An engineered wood beam is straighter and stronger than anything cut the old way from a tree.

Not so good: A floor with particle board or even higher-quality plywood as subflooring under carpeting won't feel as sturdy as one that's made from multiple layers of solid boards laid diagonally, an old technique that's now prohibitively expensive.

But guess what? Sometimes new materials--such as plastic--are the best bet.

The deteriorating quality of wood has led builders to replacement products, such as plastic outside trim. Modern wood trim rots out in just a few years unless it is scrupulously maintained and painted. "I consider [plastic] to be a major improvement, especially since I'm seeing so much rot in houses," said James Thompson of Fairfax Home Inspections Inc.

The decades have also meant changes in the walls, floors, roof, windows, doors, plumbing, heating, cooling, wiring and more. Designs, too, are different--Grandmom never had this much closet space, to say nothing of the huge kitchen-and-family-room.

"Certainly there's one major difference: The houses built today are built quite a lot better in terms of comfort, in both heating and cooling," said Larry Zarker of the National Association of Home Builders Research Center in Bowie.

That involves a lot of things, not just the mechanical systems. New houses aren't drafty. Doors are pre-hung in factories, not on-site. Windows let in light, but not heat.

"In the last 50 to 80 years, obviously, construction technology has improved. But that's kind of a double-edged sword," said Do Kim, director of engineering services at the Institute for Business and Home Safety, an insurance industry group pushing for tougher construction standards. "Eighty years ago, you didn't really know what you had to build for in terms of strain on a house, so people built conservatively."

For instance, he said, they used bigger timbers than might really have been necessary. "With knowledge, you kind of winnowed down that margin of safety."

Said Dupont, the preservation architect, "They don't build them like they used to--and a lot of that comes in economics, labor versus material costs. Historians have documented, beginning in the 19th century, labor costs going up and up, and material costs going down and down. Now, we're in a time when bringing someone on site to do the work is the expensive part, not the material."

Take something simple, like plaster vs. drywall.

Danny Patkus, a home inspector with American Home Inspection Service in Chevy Chase, has plaster walls in his 1951-built house. "It's great, except that it cracks," he said. The biggest plus: Plaster is quiet.

Builders these days, though, almost uniformly use drywall, also known as gypsum wall board or Sheetrock. It's much faster and easier to install.

To install plaster, Patkus said, "You put the lath up, then the scratch coat, then sanding, then the finish coat, then paint." That is, if you can find anyone to put up plaster at all. "For drywall, screw it up, spackle it and paint."

As much as he likes his plaster walls, Patkus said, "I know when I put an addition on this house, it's going to be drywall.

"It's cost-prohibitive to put up plaster."

Then there's the question of how you define "better." Take pipes.

"Plastic really reduced the cost and labor required, compared with either cast iron or copper," said Ron Burton, a former builder who is now assistant staff vice president for construction codes and standards at the National Association of Home Builders.

"Clearly, copper's the Cadillac. The problem is that copper costs have gone up. The question is what alternatives work really well?" Although one kind of plastic pipe--polybutylene--has been a failure, another type--polyvinyl chloride--has not had problems.

Builder Jim Kettler, president of Kettler Bros. Homes, argues that PVC plastic is actually better than copper. "A plastic pipe is much easier to work with, much easier to take care of than copper."

In his own 1950s house, he said, "I just replaced a sink last week, and I had to deal with all the copper. As a homeowner trying to do your own thing, copper's a pain."

Established regions such as the Washington area provide a sampling of housing from all eras. Neighborhoods such as Alexandria and Georgetown were built in the 18th and 19th centuries. As far as construction goes, that was "another world," said home inspector Joseph Walker of Claxton Walker Associates. "The cement was different. And energy--they were just giving it away."

Then there are the streetcar suburbs of the early 20th century, such as Northwest Washington. "I love the houses that were built in the '30s," said architect Bruce Wentworth, whose company, Wentworth/Levine, specializes in renovations. "I like them because they tended to be brick and block, very sturdy, very low-maintenance."

Most houses from this period in this area are built very well, Walker said. "Lumber was cheap and there was high-quality labor."

World War II and the great suburbanization that followed changed everything in home building. Turning out the tens of millions of houses Americans have demanded in the past 50 or so years has been a job for production builders, ever-growing companies that have brought mass-production techniques to subdivision after subdivision.

"As these production builders get bigger, customers complain there's an emphasis on quantity, not quality," said Alan Fields, who along with his wife, Denise, wrote the book "Your New House."

"As builders have gotten bigger, they've gotten extremely good at cutting every possible corner to squeeze every profit out of a house. The bad thing for consumers is that sometimes they will use shortcuts," he said.

Over the decades, quality has varied locally, Walker, the home inspector, said. For instance, in the housing boom from about 1960 until the start of the energy crisis in the mid-1970s, "a lot of cheap stuff went up." The energy crisis forced a lot of changes for the better, he said, but beginning in about 1980, once again, "quality went way downhill."

But in recent years, he said, "there's been a real change. I think it's because of the good economy. . . . Houses built in the last six years . . . are infinitely better than stuff built between 1980 and 1992."

The real issues over the past 30 years, Kettler said, have been about affordability.

As time goes on, certain things become a lot more expensive, pushing builders to innovate, he said. For instance, look at siding. Masonry is expensive and it's hard to get, so you're not going to see many stone houses.

Brick, he said, is good but expensive. Wood is high-maintenance. Metal dents. Vinyl used to crack, but now there's vinyl siding that works well, he said. The advantages: It's both affordable and low-maintenance.

Builders as a rule are good at responding to what buyers want, said Don Zeman, a building contractor who hosts "Homefront," a syndicated radio show. But sometimes that's a reason that construction quality can suffer.

"More and more builders are trying to cut costs and give people what they're asking for, and that's as much square footage of house as I can get for the money I'm willing to spend," he said.

To get that extra space at the lowest possible price, the builder needs to skimp somewhere, Zeman said. For instance, he said, he will frequently see houses under construction where particle board is used as subflooring or roof decking instead of stronger, more expensive plywood.

"There's nothing wrong with particle board in a vertical application," such as sheathing outside walls, he said, but it can sag if it spans too wide a horizontal space. Particle board may be $4 or $5 cheaper per board than plywood; multiply that by 100 or 150 boards, and the savings add up.

"Most homeowners don't know the difference, and most don't care," Zeman said. The most important things a builder can do are in the areas a buyer doesn't care about, such as the quality of framing rather than the kitchen colors, he said.

But just by following today's tougher codes and better engineering standards, builders are producing better houses than in earlier decades, said Burton, the home builders' association executive. "In terms of structure . . . we're building homes as strong as or stronger than we ever have. . . . Some of the studs aren't like they used to be, they aren't as thick as they used to be," but the final product is just as strong because it's better designed, he said.

Compared with other industries, Burton said, home building has been slow to innovate because it's a collection of cottage industries. New products spread slowly, and there's very little rigorous product testing. That has resulted in some major problems.

In recent years, some seriously flawed products have gone into use because they reduce costs, he said. Among the flawed products, all of which have failed widely in real use: polybutylene plastic pipes, fire-retardant-treated plywood roof sheeting and non-drainable synthetic stucco siding.

"We've had some glaring examples over the last few years, and it concerns builders," Burton said. "We haven't found the answer."