Wood outdoor furniture brings warmth and natural beauty to a backyard, but it faces constant attack from sun, rain, and changing humidity. Without regular care, even the sturdiest chair or table can develop cracks, raised grain, mildew, and decay. The good news is that a few simple seasonal habits, based on decades of research from the USDA Forest Products Laboratory, can keep your wood furniture looking good and structurally sound for many years.
How Sun and Water Weather Wood
Wood is a hygroscopic material, meaning it constantly absorbs and releases moisture from the air. According to the USDA Forest Products Laboratory’s Wood Handbook, wood outdoors under cover in most areas of the United States cycles around a moisture content of approximately 12% to 14%, though this varies by region. When the sun heats the wood surface, the surrounding air becomes drier, pulling moisture out and causing the surface to shrink. When rain arrives, the surface quickly absorbs water and expands. This repeated shrinking and swelling creates internal stress that roughens the surface, raises the grain, and leads to checks, cracks, and warping.
Sunlight also degrades the lignin that holds wood fibers together, leaving a silvery, weathered look. While that gray patina is sometimes desired, it signals that the wood’s protective outer layer is breaking down. Without a finish to block ultraviolet (UV) light and repel water, the wood becomes more vulnerable to decay and insect attack.
Wood Species and Their Finish-Friendly Traits
Not all wood species weather the same way. The Wood Handbook groups woods into three categories based on how easy they are to finish. Low-density softwoods with narrow latewood bands, such as white pine, western redcedar, and redwood, are easy to finish and provide excellent paint and stain performance. Their uniform structure minimizes the stress that causes finish failure. In contrast, species like southern yellow pine and Douglas-fir have wide, dense latewood bands that make them more difficult to finish; the finish often fails first over those hard bands. Diffuse-porous hardwoods such as aspen have a fine surface texture and are also easy to finish, while ring-porous hardwoods like red oak have large vessels that can leave an uneven finish unless filled.
Understanding your furniture’s wood type can help you anticipate how much maintenance it will need. Furniture made from western redcedar or white pine will generally hold a finish longer and resist cracking better than pieces made from southern yellow pine, but all outdoor wood benefits from a protective finish and regular care.
Cleaning: Mildew vs. Dirt
Before applying any finish, the wood must be clean. The USDA Forest Products Laboratory’s guide on finishes for wood decks explains that commercial deck cleaners, brighteners, or restorers can remove mildew and dirt, restoring the wood’s natural color without adding pigment. These products work well on furniture too. If the wood has turned silver from weathering, cleaning will reveal the original color when wet, though it may still look silver when dry because empty wood fibers remain on the surface. The guide cautions against aggressive scrubbing or power washing, which can remove wood from the surface, especially on softer species like western redcedar.
For mildew, a household bleach solution is effective. The guide recommends diluting liquid household bleach with 3 parts water and adding some detergent. A critical safety warning: never use a detergent that contains ammonia, because ammonia reacts with bleach to form a toxic gas. After applying the bleach solution, rinse the furniture thoroughly with water. If you plan to refinish, allow at least two warm, windy days for the wood to dry completely.
Penetrating vs. Film-Forming Finishes
The biggest decision in outdoor wood furniture care is choosing the right type of finish. The USDA guide on wood decks, which applies equally to outdoor furniture, states that penetrating finishes provide better overall performance and are easier to reapply than film-forming finishes like paint or solid-color stain. Film-forming finishes sit on top of the wood and are prone to trapping moisture, which leads to peeling and blistering. On horizontal surfaces that see foot traffic or standing water, this failure happens even faster.
Penetrating finishes soak into the wood fibers and do not form a continuous layer. They include water-repellent preservatives (WRPs), colored WRPs, and semitransparent stains. A WRP contains a mildewcide or preservative that greatly extends the life of the finish compared to a plain water repellent. The guide notes that a WRP finish has a service life of about one year on exposed surfaces, but it is the easiest finish to reapply. Semitransparent stains contain more pigment, which shields both the wood and the mildewcide from UV damage, increasing durability. Because these stains penetrate without forming a film, they will not blister or peel even if moisture enters the wood.
If you are unsure which finish to use, the guide suggests starting with a WRP. You can switch to a semitransparent stain when the furniture needs refinishing later. For vertical surfaces like chair backs and table legs, where moisture does not pool, film-forming finishes may perform adequately, but penetrating finishes remain the safer choice for all outdoor wood.
Refinishing and Sealing End Grain
The Wood Handbook’s rule for exterior wood is to refinish when the old finish has worn thin and no longer protects the wood. The Wood Handbook emphasizes that the end grain of wood is commonly 100 times more porous than the side grain, so it absorbs far more moisture and finish. Sealing end grain with a water-repellent preservative is one of the most effective steps you can take to prevent water damage and extend the life of the piece. Pay special attention to the bottom of legs, armrest ends, and any cut edges.
If the wood was previously treated with a factory-applied water repellent or a WRP, a new semitransparent stain may not absorb properly. The deck guide recommends allowing the wood to weather for 2 to 3 months before applying a semitransparent stain in such cases. Waiting up to a year can open the wood further for better absorption, but it also increases the risk of significant checking, so it is better to refinish sooner rather than later.
Seasonal Care and Storage
A seasonal routine helps you stay ahead of weathering. In spring, inspect furniture for cracks, raised grain, and mildew. Clean as needed and check that water still beads on finished surfaces. If not, apply a fresh coat of penetrating finish after the wood is clean and dry. During summer, keep furniture free of standing water and dirt. In autumn, before wet weather sets in, consider covering pieces or moving them to a covered area. Because sun and water drive weathering, reducing direct exposure to both slows the shrink-and-swell cycle that the Wood Handbook describes. For more comprehensive seasonal tasks, see our seasonal backyard maintenance checklist, the wider backyard maintenance section, and our guide to cleaning a patio and deck safely.
Whatever you do in the off-season, inspect pieces again in spring and refinish any that have worn thin before the wet months return.
Frequently asked questions
Can I use paint on my outdoor wood furniture?
Paint is a film-forming finish that can trap moisture and peel, especially on horizontal surfaces. The USDA Forest Products Laboratory’s deck guide recommends penetrating finishes for wood exposed to weather. If you choose to paint, it may perform better on vertical surfaces like chair backs, but expect more frequent maintenance.
How do I clean mildew without damaging the wood?
Use a diluted bleach solution (3 parts water to 1 part bleach) with a small amount of detergent, but never use ammonia-based detergents, as mixing bleach and ammonia creates toxic gas. Rinse thoroughly and allow the wood to dry for at least two warm, windy days before refinishing. Avoid aggressive scrubbing or power washing, which can erode soft wood fibers.
How often should I refinish my wood furniture?
The service life of a water-repellent preservative finish is about one year on exposed surfaces, according to the USDA deck guide. Semitransparent stains last longer because the added pigment blocks UV light. Refinish when the old finish has worn thin, which is the point the Wood Handbook uses for exterior wood.
For more detailed guidance on cleaning, protecting, and storing all types of outdoor furnishings, visit our outdoor furniture care hub.
