What goes on inside a bland brown building in an Upper Marlboro office park makes a big difference in what goes into constructing your home.

Each day, the staff of the National Association of Home Builders Research Center crushes pipes, simulates gale-force winds, breaks walls and scrubs sink surfaces -- all to determine whether the materials used in home construction work well under stress.

The center was founded in 1964 as a subsidiary of NAHB, a District-based industry group. For the building industry, it is similar to Underwriters Laboratories Inc., which tests household appliances, by evaluating and testing home building products and materials. Just like UL and other testing labs, the NAHB Research Center has its own logo, which manufacturers stamp on the packages of products that pass the tests.

As part of its 40th anniversary, the center opened its doors last week to industry insiders, builders, contractors, government officials and some members of the general public for a guided tour.

In addition to researching home design and construction, the center studies issues such as land use, sustainable housing and special-needs housing. It has constructed a cluster of demonstration houses in Prince George's County that showcase technologies such as those used to build environmentally conscious homes. It runs ToolBase Services, a housing industry Web site with information on building materials. Home building insiders also lean on the center for market research data.

However, its laboratory -- an understated, wide-open space that looks less like the high-tech crime labs on CSI and more like a Home Depot -- is where the real work begins.

Manufacturers pay the center to have its engineers and technicians subject products to all sorts of punishment to determine if they meet standards set by the American National Standards Institute, the American Society for Testing and Materials and the like. Researchers also make sure product performance is up to par with building and plumbing codes, as well as state and local regulations.

For many manufacturers, the center provides assurance to customers that their products were independently tested, said Robert L. Hill, the director of the testing lab and its certification program. The NAHB Research Center logo on product packages signals to consumers that what they bought will work, he said.

For instance, Paul Downs, owner of Waldorf Marble Inc. in Charles County, said in a telephone interview that he pays $400 to $650 a shot for the lab to test his custom cultured-marble sinks. For his product to be certified, the cultured marble -- a blend of polyester resin, crushed marble and other materials, cured to a specified hardness -- is required to be tested four times a year and pass American National Standards Institute standards. In addition to having no cracks or blemishes before testing begins, the product has to pass minimum levels of workmanship and finish, structural integrity, wear, how easy it is to clean, resistance to staining, and more.

Downs said the NAHB Research Center has been testing his 27-year-old company's product for 10 to 15 years.

"They've always been eager to help us with any problems or ways to make the product better, if necessary," Downs said.

Case in point: During a scratch-resistance test, the lab staff noticed that the gel coat applied to the sink was not thick enough, Downs said. There should be about 20 to 25 millimeters of gel coat on the product. The center suggested applying more in certain areas of the sink, such as the drain area, he said.

Hill began the recent lab tour in the attic.

Or rather a large room designed to look somewhat like an attic. Its walls are painted white; floors are uncovered; fluffy white insulation is scattered on the ground. A blowing machine, about chest-high, is near the door.

The lab staff is testing loose-fill fiberglass insulation -- a kind that that might be used in an attic -- to see how much area a bag of the product would cover. The material conforms to the spaces where it is installed, usually hard-to-reach places. It's funneled into building cavities using a blowing machine.

Earlier, research center officials had visited the manufacturer and selected bags of the product at random. They then measured how many square feet a bag of insulation covered after being spread out by a commercial blowing machine.

Some pieces of the fiberglass wool were also put under a heat flow meter to measure the thermal resistance, or the R-value, of the material. This is the standard measure of how well a product insulates; the higher the R-value, the greater the effectiveness of the insulation.

"If it meets the standard, they get to use our certification logo," Hill said.

Hill showed off the center's logo on a previously tested bag of insulation that passed muster.

"It gives the consumer confidence that this company is willing to have a third party randomly test the product to make sure that it will perform like it's advertised," he said.

Moving on, he stops by the water torture test, where several different sink plumbing fixtures are lined up to endure thermal shock. They have to withstand the pressure of 500 alternating hot and cold water flows, or they won't be up to plumbing codes.

This test is supposed to simulate the action of turning on and off a faucet, Hill said, "to make sure it won't crack" under the temperature pressure and frequent use.

Nearby a machine scrubs white pieces cut from several sink basins 10,000 times to see if they maintain their original appearance. It was on scrub number 7,560.

The tester contains a highly abrasive solution. To meet the standard, the surface finish should not wear through and should not lose more than 2 percent of its color's brightness after the scrubbing.

"It's amazing, some of the things that you take for granted that you don't realize, " said Dawn L. Faull, program manager of the Concrete Home Building Council for NAHB. "You don't realize that when you're scrubbing your kitchen sink, it actually was tested to make sure it's not going to come off."

The sinks also must endure an impact-resistance test: Testers drop a 41/2-pound iron skillet on them from a foot away to make sure they don't crack or fracture. They also perform a deflection test, in which they place a 200-pound weight in the sink and then measure how much the sink has bent after the weight is removed. To pass, the sink must be bent no more than 0.01 inches 10 minutes after the weight is gone.

Juan Camilo Patino, sanitary ware marketing manager for ColCeramica SA of Bogota, Colombia, said his company buys many of the research center's reports. He said he was on the tour because it was important to him to see the source of the data "to know the kinds of tests, procedures they had for the different housing products."

Alejandro Espinal, president of market research company AF International of Miami, brought Patino, one of his clients, on the tour to see the center's offerings. He was particularly struck by the plumbing fixture test.

"That's one of my industries," said Espinal, who has worked with the center for about 41/2 years, buying its market research for his foreign clients.

"It's good [that they] have everything in house, in the same place," he said.

"Every time I get to know more about the center, I will see another opportunity to push the information they have to companies in Latin America or in Mexico . . . in the construction business that want to come to the U.S. and get to know the trends of the market, the size of the market, the size of the opportunity," Espinal said.

He plans to urge his customers to use the center for independent tests of their products.

In the center of the lab rests the universal test machine, which is capable of pulling apart or crushing materials with a 200,000-pound force. The apparatus looks like a cross between a giant recycling can crusher and a taffy puller.

"You can do all sorts of tests in this machine," Hill said. "We measure how much force it takes to pull a nail out of a board. We'll put a great big wall in here and figure out how much load it takes to crush it."

Concrete walls and steel reinforcements have suffered under the machine. In this test, a plastic-like material is being stretched by forceps to measure how much force it takes to break it.

"It's part of our internal quality assurance thing," Hill said. "We'll test this. Then a dozen other labs will test it. Then, we'll compare the results to see, 'Are we getting really the same thing?' "

In a previous test, the equipment was used to monitor how much weight a grab bar could hold. Grab bars, which are attached to bathroom and shower stalls, often are used to assist people who use wheelchairs or want a bit of support.

Most building codes require that grab bars withstand a 250-pound load.

N. Susan Nelson, a research utilization specialist at the Department of Housing and Urban Development, said the grab bar test would be useful for people of different sizes, especially those who may be large or a little clumsy in the shower.

"That [test] was the most impressive part to me because it was something that would impact most people's day-to-day lives," she said.

The research center is one of HUD's contractors, Nelson said, and she and her colleagues often assemble information materials based on NAHB's research.

"They were testing the standards, which is reassuring to people like me because we're always giving information out that we believe to be true," she said. "We like to put out the truth."

On the other side of the universal test machine, the 150,000-pound shear wall tester awaits. The apparatus holds a square-frame wooden wall, with locks holding it upright and in place.

The machine can slide it back and forth, by large or small increments. How much force can the wall withstand before it fractures? How does the wall splinter? Is there a way for an engineer to design a wall that could withstand forces of nature?

"When the wind blows on the side of the house or when an earthquake hits and it starts to shake, a wall like that will keep it from breaking, will keep it from bending," Hill said of one experiment. The machines pushes the wall on one side and records how far it can push, at what kind of load and how fast.

That day's test was just a simulation for visitors -- the machine's bottom clamps were unattached, so the wall slid more easily and further than it should have.

In the back end of the lab sits the wind chamber. Here, researchers will mount a window, for example, and pressurize the box to simulate the wind blowing on a house to see if a window will leak.

Near another wall, a large rectangular box holds the accelerated ultraviolet tester. The device emits high-intensity ultraviolet light that is trained, for instance, on a piece of an outdoor spa. The test is done to see if the object "fades or cracks under the sunlight," Hill said.

Next to the device is a hot tub. Researchers, using a wooden stick from which hangs a clump of foot-long blond hair, test to see if the jets will suck up the hair strands. This test is to prevent drowning accidents, especially those involving children, Hill said.

The lab also has an air cannon test outside, but for the tour, videotape illustrated the point of the projectile test.

"We will shoot different materials at different things to see how it's going to perform in a hurricane or tornado," Hill said. For example, pieces of shingles and 2-by-4 wood are launched to see if the glass window can withstand the impact.

"Those shingles didn't break the window that time," said Hill, commenting on a test shown on the TV screen. "It wasn't going that fast."

Patricia H. Adkins, chief operating officer of the Home Safety Council, a nonprofit organization originally founded by Lowe's Home Improvement Warehouse, said that on a previous tour, she had witnessed projectiles hurtling toward a target. She was told that the staff was trying to assess "what damage a projectile would do, to determine how stationary and stable the window is."

Adkins said this second visit was particularly informative for her and the Home Safety Council. Her group, formed in 1993, focuses on giving out information on home safety, "particularly unintentional injuries in the home," she said. Key topics for the group are fires and burns, poisoning, falls, drowning, suffocation and choking, she said. Her organization is thinking of acknowledging corporations and manufacturers that make innovative and safe products by using the NAHB Research Center's lab for safety tests.

Not everyone who took the tour was in the building business. Jeanne Ilchuk, a Unix systems administrator for the Washington Research Library Consortium, said she wasn't too impressed with the tests. She has seen similar ones in Consumer Reports magazine.

"But I've worked for this office park for 10 years, and I always wondered what they did in here," Ilchuk said. "And so, I was like, 'This was very cool.' I finally found out."

Robert L. Hill, head of the testing lab at the National Association of Home Builders Research Center, talks about tests done at the abrasion test station.Products that are tested and approved by the center get their seal of approval."The Racker" tests how easily a wall will break and bend, simulating the forces of wind or an earthquake.Research analyst Mark Wagner shows the results of a test conducted on the universal test machine. Research analyst Mark Wagner works with the universal test machine, which can exert 200,000 pounds of force on various building products.