Cedar is a beautiful, durable wood that makes an excellent material for outdoor projects. When properly finished, cedar can withstand the elements for many years while retaining its attractive reddish-brown color. Here is a comprehensive guide on how to finish cedar lumber to protect and beautify your outdoor cedar structures.
Choosing the Right Cedar Finish
When deciding on a finish for outdoor cedar, consider the level of protection needed and the desired aesthetic.
Oil Finishes
- Penetrating oils like tung oil deeply soak into the wood pores without leaving a thick film on the surface. This allows the natural grain to show through while providing decent water resistance. Reapplication is needed every 1-2 years.
- Teak oil contains mildewcides to help resist mold and mildew. It provides good protection for horizontal surfaces like decking. Teak oil needs reapplying every 6-12 months.
- Linseed oil is an inexpensive option derived from flaxseed. It penetrates well but offers minimal water resistance. Linseed oil needs reapplication every year.
Water-Repellent Wood Sealers
- Water-repellent sealers contain transparent waterproofing agents like paraffin, silicone, or waxes. These seal the pores against moisture while allowing the wood’s natural color to show through. Reapply every 1-3 years.
- Spot-treat with these sealers to protect end-grain cuts on railings, benches, etc which are more absorbent.
Film-Building Sealers
- Spar urethanes offer the best all-around protection by forming a thick protective film on the wood’s surface while allowing some breathing. Reapply every 2-4 years.
- Varnishes provide a shiny transparent film. Exterior varnish holds up better than interior types. Reapply varnish every 1-2 years.
- Painted finishes totally coat the wood for excellent water protection. Repaint as needed when wear shows through every 3-5 years.
Prepping and Sanding the Wood
Proper prep work ensures the finish adheres well and lasts longer:
- Allow fresh-cut cedar to dry out for at least 2-3 weeks before finishing to prevent cracking.
- Sand with 80-100 grit paper to remove mill glaze and roughen the surface. Always sand along the wood grain.
- Before the first coat, wipe away all sanding dust using a cloth dampened with mineral spirits.
- On previously finished wood, thoroughly strip old sealers using chemical strippers or sand down to bare wood.
- Spot-treat any darkened stain blotches, knots, or mildew spots with oxalic acid (wood bleach). Rinse thoroughly.
- Replace any cracked or damaged boards prior to refinishing.
Applying Cedar Finishes
Careful application techniques will maximize the durability and aesthetics of the finish:
- Always read and follow the manufacturer’s instructions for full drying times between coats.
- Use a high-quality natural bristle brush to gently work the finish into the grain. Avoid excessive brushing.
- Maintain a wet edge as you apply the finish to prevent lap marks. Work from one end of the board to the other.
- Apply along the wood grain direction. Use thin, even coats – no drips or sags.
- Coat all surfaces – don’t miss the ends and undersides. Apply at least 2 coats for optimal protection.
- Apply water-repellent sealers annually. Refinish film-building finishes when wear shows through.
- Lightly sand between coats using 220-320 grit sandpaper to improve adhesion.
Maintaining Your Finished Cedar
With proper care, your finished cedar project can stay beautiful and protected from the elements:
- Inspect sealers and film finishes annually before winter. Look for cracking or peeling. Refinish worn areas.
- Wash the wood annually using mild detergent and a soft brush. Avoid pressure washing.
- Lightly sand and recoat film finishes when the film starts wearing thin.
- Apply fresh water-repellent sealer every year for maximum protection.
- Remove mildew immediately using wood cleaner followed by light sanding and spot sealing.
- Consider applying a UV-inhibiting sealer like paste wax if the wood will get intense sunlight.
With the right finish and proper application, your outdoor cedar structure can withstand rain, snow, and sun while accentuating the elegance of real wood. Follow these tips for finished cedar that stays beautiful and protected from the elements for many years.
Frequently Asked Questions About Finishing Outdoor Cedar
How long does it take for cedar finish to fully cure?
Cedar finish cure times vary by product, but expect 72 hours minimum between coats. Oil-based finishes take longer – up to 2 weeks to fully harden and become water-resistant. Read the product label for the manufacturer’s recommended cure time.
What is the best cedar finish for frequent rain and snow?
For high exposure to precipitation, spar urethanes provide excellent protection. The resin-based film repels water while allowing the wood to breathe. If you prefer oils, teak oil contains extra water repellents.
How do I restore grey weathered cedar?
Greyed cedar can be renewed. First use a wood cleaner or oxalic acid to remove mildew stains. Lightly sand then apply a wood brightener as per the label instructions to restore the color. Lastly, refinish the rejuvenated wood.
What do I do if finish starts cracking or peeling?
Cracking or peeling means it’s time to refinish. Use a paint and varnish remover or media blaster to completely strip the old finish if needed. Sand, clean, bleach spots if necessary, then re-coat with your desired cedar finish.
Can I use the same cedar finish on indoor projects?
You can, but exterior finishes are tougher. For indoor cedar furniture or millwork use an interior varnish, polyurethane, or oil like Danish, tung, or walnut. Don’t use exterior finishes inside – they have stronger fumes.
Conclusion
Finishing outdoor cedar correctly means your project will retain its natural beauty for years while withstanding sun, rain, snow, and moisture. Prepare the wood properly, choose a protective finish suitable for the project type and exposure, and apply with care following the manufacturer’s directions. Well-maintained outdoor cedar develops an elegant silvery patina. Follow these finishing best practices and your cedar will gracefully withstand the elements.