Nail your home renovation budget

With the real estate market heating up, it appears that American homeowners are ready to start remodeling again.

After years of decline, home-improvement spending increased 9% in 2012, according to the Joint Center for Housing Studies at Harvard University, which predicts a double-digit surge for 2013.

Planning to get in on the renovation revival with a project of your own? You'll want to utilize a tool that some home appraisers say was too often neglected during the last housing rush: a budget.

Establishing a project cap and looking for painless ways to reduce your overall cost will stop you from spending more than you can hope to recoup when it's time to sell.

Here, a primer on setting -- and sticking to -- a renovation budget:

Find your number. To figure out what's safe to spend, you'll need to determine how much of your home's value is represented by the room you're planning to redo, says Omaha appraiser John Bredemeyer, a spokesperson for the Appraisal Institute, which sets national standards.

In general, says Bredemeyer, the kitchen accounts for 10% to 15% of property value; bathrooms, 5% to 10%; half-baths, 5%, and a finished basement or attic, 10% to 15%. To calculate your cap, multiply that percentage by your property value. So if you're planning, say, a major kitchen reno on a $400,000 home, you wouldn't want to spend more than $60,000.

Use your local municipal tax valuation or a site like Trulia.com to gauge how much your home is worth. You'll typically get a conservative estimate from both because they're often slightly behind the market. And, of course, budget to spend less than the calculation if that's more than you can afford.

Limit major construction. When remodeling existing space, you can trim your outlay by minimizing changes to the footprint, says Charleston contractor Mike Eippert. Any wall you don't move or remove will save $3,000 to $5,000. Ask your contractor if it's possible to avoid stripping open the walls and ceilings. That could save you another $2,000 to $5,000, even after workers make some temporary holes to snake in new wiring and pipes.

Similarly, putting new bathroom or kitchen plumbing fixtures and appliances in the same spot their predecessors were located could slash your project cost by $2,000 to $3,000, says Kansas City, Mo., contractor Paul Young, because the existing pipes and electrical lines can be reused.

Do the right things yourself. Homeowners often tackle interior painting themselves because it is low tech, requires few tools, and comes at the end of the project, when funds may be running low. Good move. That could save you more than $1,000 a room.

If you want a bigger sweat-equity bump, consider doing your own demolition too, says Bruce Irving, a Cambridge, Mass., realtor and renovation consultant.

As long as you can do the job correctly and safely, pulling out appliances, plumbing fixtures, cabinets, and tiles could save you $2,000 to $5,000 or more. Check diynetwork.com for a how-to refresher, and be sure to walk through the process with your contractor before you start.

Look for savings on the priciest items. You don't have to forgo upscale features to keep your project affordable. If you want stone kitchen countertops, for one, choosing a simple squared-off edge profile (called "eased") rather than a more complex pattern could save $500 to $1,000, says Adrienne Dorig Leland, a kitchen designer in Eau Claire, Wis.

Ask local appliance retailers about scratch-and-dent and open-box sales; the damage may be minor and in a low-visibility spot, and you could trim $200 to $1,000 per appliance.

For a high-end commercial range, try an appliance reseller, like Green-Demolitions.com, where you could pick up a lightly used Viking, say, for 25% to 50% of a new one's $6,000 price tag. Knowing your kitchen centerpiece didn't bust your budget will let you enjoy cooking on it all the more.