Upkeep for outdoor wood furniture
1. CLEAN AND SEAL
Cleaning and sealing any outdoor wood is not much different from doing the same thing for a wood deck. Outdoor wood tables, chairs, fencing, wood play sets, arbors and so forth all take the same abuse from Mother Nature. If you fail to maintain outdoor wood, it eventually will rot and crack to pieces. Chemically treated lumber is able to resist rot for decades. Some wood, including redwood, cedar and teak, contains varying degrees of natural preservatives. But water that soaks into any of these wood species will cause them to crack.
2. HOW CRACKS HAPPEN
Cracks start out as crazing in the finish, called checking. Water that reaches the wood causes it to expand. As it dries, it contracts. This movement creates tiny cracks. If water gets into the cracks, it soaks deeper into the wood, causing even greater expansion and contraction forces that cause the cracks to get deeper and wider.
3. USE REPELLENT
You can see why it's important to treat all wood with a water repellent on a regular basis to prevent water from getting into the wood. Do this every other year or so, and your outdoor furniture and play sets will look fantastic.
4. HIGH PRESSURE HURTS
Do not use a pressure washer to clean outdoor wood. It absolutely will damage it. The high-pressure stream of water erodes the softer, lighter-colored bands of spring wood that are found between the darker bands of summer wood grain.
Allow the wood to dry well after it's clean. The washing process almost always raises the grain of the wood. This means you'll have to sand it to get it back to that smooth furniture finish. Don't skip this important step. A palm sander works great for this project. Use a medium aluminum oxide sandpaper. This paper self-sharpens as it's being used.
6. SEAL THE DEAL
Once the wood is sanded, you should seal it with a pigmented synthetic resin water repellent. Do not use an oil-based product. Most oil-based sealers are food for mildew and algae. The manufacturers place mildewcides and algicides in the products to slow down the growth, but water and sun break down these chemicals. The colored sealers will keep the furniture looking spectacular. Clear sealers will gray rapidly. Work in the shade when applying the sealers. Some sealers require you to apply two coats within 15 minutes of each other to get maximum protection. Working in direct sunlight can shorten this time dramatically, leading to ugly spotting and overlaps.
7. ALL HANDS ON DECK
Staining and sealing outdoor furniture is quite different from sealing a deck. It requires a fine touch so your brush strokes are not seen and you don't create any overlap marks. You have to maintain a wet edge with the sealer, which means you stain each piece of wood completely -- you don't stop working until you reach the end of that piece or it intersects with another piece of wood. Failure to do this can result in very unattractive overlaps where the color of the sealer seems darker at the overlap area.