You know how Dr. Oz says that if you keep your body fit and your mind nimble, you’re likely younger than your chronological years? The same principle applies to your house.

An out-of-shape house is older than its years and could lose 10% of its appraised value, says Mack Strickland, an appraiser and real estate agent in Chester, Va. That’s a $15,000-$20,000 adjustment for the average home.

But good maintenance can even add value. A study out of the University of Connecticut and Syracuse University finds that regular maintenance increases the value of a home by about 1% each year.

So if you’ve been deferring maintenance, or just need a good strategy to stay on top of it, here’s the simplest way to keep your home in good health.

Focus on Your Home’s #1 Enemy

If you focus on nothing else, focus on moisture — your home’s No. 1 enemy.

Water can destroy the integrity of your foundation, roof, walls, and floors — your home’s entire structure. So a leaky gutter isn’t just annoying; it’s compromising your foundation.

Keeping moisture at bay will improve your home’s effective age — or as Dr. Oz would say, “real age” — and protect its value. It’ll also help you prioritize what you need to do. Here’s how:

Follow This Easy 4-Step Routine

1.  When it rains, actively pay attention. Are your gutters overflowing? Is water flowing away from your house like it should? Is water coming inside?

2.  After heavy rains and storms, do a quick inspection of your roof, siding, foundation, windows, doors, ceilings, and basement to spot any damage or leaks.

Related: How to Tell if You Have a Drainage Problem

3.  Use daylight savings days or the spring and fall equinox to remind you to check and test water-related appliances like your washer, refrigerator, water heater, HVAC (condensation in your HVAC can cause leaks) or swamp cooler, and sump pump. It’s also a great time to do regular maintenance on them. Inspect any outdoor spigots and watering systems for leaks, too.

4.  Repair any damage and address any issues and leaks ASAP.

Don’t procrastinate when you spot minor leaks or drips inside your house. Ongoing small leaks can slowly erode pipes and fixtures, and even cause mold and mildew issues you won’t notice until it’s too late.

Say you’ve got a bit of cracked caulk around the kitchen window. It may not seem like much, but behind that caulk, water could get into your sheathing, causing mold damage and rot. Before you know it, you’re looking at a $5,000 repair that could have been prevented by a $4 tube of caulk and a half hour of your time.