Nearly 30 percent of homes in the United States were built before 1940. That fact, coupled with the additional fact that both Martha Stewart and Tim Allen are highly revered members of our society, means that the remodeling/renovation industry is likely to remain strong, as the do-it-yourself drive continues. While the rate of growth in remodeling has actually slowed, the market is expected to grow an average of 4 percent to 5 percent through the end of the decade. The National Association of Home Builders (NAHB) estimates that Americans will spend $130.6 billion on remodeling in 1998; $47.3 billion of that total is expected to spent on maintenance/repair and $83.3 billion is expected to be spent on improvements.

But does emptying your wallet on these improvements make sense in the long run? How much will you actually recoup? According to Remodeling magazine, updating and remodeling kitchens and baths add the most value to a home. In some markets, remodeling projects will return more than 100 percent of the cost if the home is sold within a year; if the home is kept longer than one year, returns should increase. Here are the national averages for popular remodeling projects, according to Remodeling magazine's 1996-1997 Cost vs. Value Report:

*MINOR KITCHEN REMODEL (replace cabinet doors, oven and cooktop, laminate countertops, sink, faucet and floor, repaint): Job Cost: $8,507; Resale Value: $8,030; Cost Recouped: 94%

*BATHROOM ADDITION (add a second bath to a house with 1 or 1.5 baths; include ceramic tile and linen closet): Job Cost: $11,645; Resale Value: $10,593; Cost Recouped: 93%

*MAJOR KITCHEN REMODEL (redesign kitchen, replacing all of the above, plus built-in microwave, custom lighting, island): Job Cost: $21,262; Resale Value: $19,190; Cost Recouped: 90%

*MASTER SUITE (in a house with 2-3 bedrooms, add a 24-by-16 master suite with walk-in closet, whirlpool tub, separate shower): Job Cost: $36,472; Resale Value: $30,350; Cost Recouped: 84%

*ATTIC BEDROOM (in a 2-3 bedroom house, convert unfinished attic space with bedroom and shower/bath): Job Cost: $22,840; Resale Value: $19,084; Cost Recouped: 84%

*TWO-STORY ADDITION (first-floor family room and second-floor bedroom with full bath): Job Cost: $55,687; Resale Value: $46,236; Cost Recouped: 83%

*FAMILY ROOM ADDITION (add a 16-by-25 room with skylights, hardwood tongue-and-groove floor, fireplace): Job Cost: $31,846; Resale Value: $26,483; Cost Recouped: 83%

*BATHROOM REMODEL (update existing bath with new tub, toilet, vanity, medicine cabinet, lighting, tile): Job Cost: $8,423; Resale Value: $6,480; Cost Recouped: 77%

*REPLACE WINDOWS (10 new 3-by-5 aluminum-clad windows with trim): Job Cost: $6,112; Resale Value: $4,536; Cost Recouped: 74%

*REPLACE SIDING (1,250 square feet of new vinyl or aluminum siding and trim): Job Cost: $5,458; Resale Value: $3,983; Cost Recouped: 73%

*DECK ADDITION (16-by-20 deck of pressure-treated pine, including built-in bench, railings, and planter): Job Cost: $6,172; Resale Value: $4,459; Cost Recouped: 72%

*HOME OFFICE (convert existing room into office with custom cabinetry and rewiring for electronic equipment): Job Cost: $8,103; Resale Value: $5,423; Cost Recouped: 67%

During the recent 31st annual National Association of Real Estate Editors conference in Las Vegas, panelist Steve Bottfeld, executive vice president of Marketing Solutions, announced his seven "secret" trends affecting the housing industry. Among them: light -- obtaining more of it is a worthwhile pursuit, he said. Skylights, walls of windows, and greenhouse windows are all likely to boost property values.

If you've narrowed your choices to remodeling your older home or building a new one, consider this: Lumber prices have increased sharply during the 1990s, making new homes less affordable. The average price of lumber was $200 per 1,000 board feet during the 1980s; during the 1990s, prices have averaged more than $300 per 1,000 board feet. According to the NAHB, lumber price increases are largely attributable to environmental restrictions on timber harvesting in the forests of the Pacific Northwest. Lumber and wood products account for one-third of the cost of materials used to construct a home. The average 2,000 square-foot home uses nearly 16,000 board feet of lumber and 6,000 square feet of structural panels. At $400 per 1,000 board feet -- hardly an eyebrow-raising figure right now -- the lumber package for a 2,000 square-foot home is a steep $10,000.

Something else you might want to consider before you build or buy another home: Home prices increased more quickly than inflation in most areas of the country during the July-to-September quarter, 5 percent higher than last year and more than double the overall 2.2 percent increase in consumer prices for the same period. According to the National Association of Realtors (NAR), the national median home price rose $6,000 to $126,500 during the above-mentioned period. Prices rose in all regions of the United States. Although the South led the increase, even the troubled Northeast experienced a price hike.

So are you going to join the ranks of Tim and Martha? Snap up your overalls, put on your tool belt, and get out your paint brush -- or hire someone else to do it. Your bank account might thank you for it later.