You should generally not use standard polyurethane on cedar, especially outdoors. While safe for indoor cedar, polyurethane creates a rigid film that breaks down, peels, and traps moisture, which ruins the wood’s natural beauty. Use oils or stains instead for better protection and easier maintenance.
Polyurethane forms a hard, non-breathable shell. Cedar, however, is a porous, living material that expands and contracts with changes in humidity and temperature. When you seal it with an impermeable coating like polyurethane, that natural movement is restricted, increasing the risk of cracking and splitting.
For optimum surface durability, the first coat may be of high gloss lacquer followed by one or two coats of matte or satin lacquer. On smooth cedar, a final coat of wax will impart a rich sheen to the wood. Clear varnish is recommended only for smooth surfaces. It will inevitably add a richer, darker tone to cedar.
Cedar-Seal dries clear and maintains the wood's oil content for years to come. Cedar-Seal may be applied before water based stains orr before painting with any water based paint product. Natural “greying will occur if used as a stand-alone coating without the use of pigments.
For cedar columns, use a high-quality spar urethane or water-based sealer designed for outdoor wood. Spar urethane offers superior UV protection and flexibility, preventing cracking from weather changes. Thompson's Water Seal provides water repellency but less UV defense.
If you prefer to preserve the original color of your cedar fence, there are steps you can take to slow down the greying process: Seal and Protect: Applying a high-quality wood sealant or finish to your cedar fence can help shield it from UV radiation and moisture, preserving its natural color for a longer time.
Stains protect the boards from moisture and look great, but unlike penetrating oils, they do not replenish the natural oils extracted by the sun. They are designed to erode over time, often unevenly, and leave the timber unprotected and unsightly.
Remove Old Finish and Sand
You'll get the best results from your polyurethane topcoat if you remove any old paint, varnish or other finishes before polyurethane application. For a smooth coating, you'll want the surface to be as smooth as possible. Prepare the wood by sanding it with a sanding block or orbital sander.
Finally, clear finishes are ideal if you want to maintain the natural look of cedar wood while protecting it from the elements. These finishes allow the beauty of the wood grain to shine through without adding any color, making them perfect for projects where the natural appearance of the wood is a key feature.
Minwax® Fast-Drying Polyurethane
This oil-based clear sealer protective coating protects and adds long-lasting beauty to woodwork, furniture, doors, cabinets and floors. It's one of the most durable coatings for wood protection against scratches, spills and more, and is a clear coat.
Substances such as para-phenylenediamine or cresol help the wood to last long. However, another method of preservation is to combine wax and oil such as carnauba, bee and candelilla waxes along with linseed, sunflower and jojoba oils. These will help prolong the life of your cedar wood and make it more durable.
Sand the wood thoroughly to ensure a smooth surface for a professional finish. Use a quality wood stain to enhance the natural beauty of the cedar, and choose a finish that will protect the wood from moisture and sunlight.
PERFECT FOR CEDAR
Nova's ExoShield Tung oil wood finish is a high-quality deep-penetrating oil finish that protects and beautifies all exterior and interior wood projects, including decking, siding, fencing, paneling, soffit, exposed beams, and outdoor furniture.
If you do not stain your cedar fence, it will turn gray, dry out, and may crack over time. Staining protects against UV damage, moisture, and other elements, helping to preserve its color and life.
Is It Better to Apply Polyurethane with a Brush or Rag? Both have their advantages: A rag works best for contoured surfaces or when you want a really smooth, thin finish using wipe-on poly. A brush (either natural or foam) is better for flat surfaces or when you need to build up thicker coats.
The surfaces of finished Western Red Cedar decks, siding and trim boards exposed outdoors inevitably become dirty and can also be discolored by mildew, algae and moss. These natural elements slowly erode the finishes and as a result, all finishes applied to cedar require regular cleaning and maintenance to perform.
2. Do redwood and cedar need to be sealed or stained? While both woods naturally resist decay, applying a quality sealant or stain helps retain their colour and offers added protection from moisture and UV rays. It's a good idea to reapply every 2–3 years, depending on sun exposure.
Two coats of penetrating oil-based stain on textured cedar will provide longer service life than one coat, but only if the wood will accept the second coat. Stir the stain thoroughly during application to prevent settling and color change. Avoid mixing different brands or batches of stain.
When you use vinegar on polyurethane finished wood, the acid in the vinegar breaks down the finish and starts to pit the finish. These pits trap sand and along with the acid will eventually strip the polyurethane.
Finish if you want to provide some protection to the cedar from minor abrasions. Use bleach, oils, semi-transparent and solid body stains and opaque finishes, if you want to change the wood's appearance.
Woods That Are Difficult to Stain
Cedar naturally contains oils that help to repel moisture and insects, which makes it a great choice for siding. However, over time these oils can break down, leaving the wood vulnerable to damage. Sealing your cedar siding helps to protect it from moisture, UV rays, and pests, which can help extend its lifespan.
We always recommend two coats of stain for any wood project, but you should only apply as much stain as the wood can absorb. Extremely dense hardwoods may only be able to absorb one coat of wood stain. The general rule of thumb is to apply only as much deck stain as the wood can absorb.