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In honor of MONEY’s 35th anniversary, a 35-hour plan for spring and fall maintenance.

By Asa Fitch, Amanda Gengler, Josh Hyatt and Ismat Sarah Mangla. Excerpted from “35 Minutes to Riches,” October 2007 MONEY.

Devote four Saturdays a year to home maintenance and you can prevent costly repairs later. The biggest threat: water damage, which can lead to rotting and mold, says Dave MacLellan, co-author of The National Home Maintenance Manual and founder of Housefixit.com.

FALL
DAY ONE:
Clean the gutters—clogs can cause water to back up into the eaves, and the acid produced by leaves and bird droppings eats away at metal. For better energy efficiency, change the air filter in your furnace.

DAY TWO:
Water can seep in around windows and doors, so open each one to check whether dirt has clogged the weep holes, the small drains in the tracks. Unclog them with a straightened paper clip. Next circle your home's exterior looking for gaps around windows and doors. Fill them with caulking. Also watch for protruding nails. As the temperature changes, the holes expand and contract, pushing out the nails. Replace them with galvanized nails.

SPRING
DAY ONE:
Inspect your roof from a ladder (walking on it can cause damage). Look for shingles or tiles that have loosened, slipped or blown off. You'll likely want to hire someone to install new shingles (the smallest project will start at $250); ignore the problem and one day you may have to spend $11,000 to $30,000 on a new roof.

DAY TWO:
Repeat the fall inspection of your walls. Change your furnace's air filter again.

© Time Inc. Reprinted with permission. Does not constitute MONEY endorsement of Lowe's or any products/brands.