Redwood is a beautiful and durable wood that is ideal for many outdoor uses. However, left untreated, redwood is still susceptible to rot, cracking, warping, and discoloration when exposed to the elements. Applying a protective finish can help redwood maintain its beauty and resist damage when used outdoors. Here is a comprehensive guide on how to properly treat redwood for outdoor use.
Selecting the Right Finish for Redwood
Choosing the appropriate finish is the first critical step in protecting outdoor redwood. Consider the following factors when selecting a finish:
Oil vs. Sealant
Oils – Penetrate deeply into the wood grain to waterproof and protect the interior wood cells. Require frequent reapplication. Best for horizontal surfaces like decks.
Sealants – Form a protective film on the wood’s surface. Provide longer-lasting protection. Ideal for vertical surfaces like siding, fences, etc.
Transparent, Semi-Transparent, and Opaque Finishes
Transparent – Allow the natural color and grain to show through completely. Offer the least amount of protection.
Semi-Transparent – Provide a hint of color while letting some of the grain show through. Offer medium protection.
Opaque/Solid – Obscure the wood grain with a layer of opaque paint. Offer the most protection but completely change the look.
Water-based vs. Oil-based
Water-based – Made with water-soluble resins. Easier to apply and clean up. Better for the environment. Require more frequent reapplication.
Oil-based – Made with solvents. Provide better penetration and protection. Require proper cleanup and disposal.
Finish Ingredients
Look for finishes formulated specifically for redwood and exterior use. Ideal ingredients include:
- UV blockers – Prevent damage from ultraviolet light.
- Water repellents – Cause water to bead and run off the surface.
- Mildew inhibitors – Prevent mildew growth.
- Insecticides – Deter wood-boring insects.
Preparing Redwood for Finishing
Proper prep is crucial for the finish to adhere and perform correctly. Follow these steps:
Cleaning
Use a stiff brush and cleaner formulated for wood to remove dirt, mildew stains, algae, and other debris. Rinse thoroughly. Allow wood to dry completely before finishing.
Sanding
Lightly sand with 120-150 grit sandpaper to smooth any rough spots and open the wood grain. Always sand along the direction of the wood grain. Never use steel wool.
Repairs
Fill any cracks, holes, or defects with a flexible wood filler designed for exterior use. Allow filler to dry as directed, then sand flush.
Moisture Testing
Use a moisture meter to test moisture content. Only apply finishes when moisture reading is below 15%. Higher moisture will prevent proper adhesion.
Choosing an Application Method
Consider these application methods when treating outdoor redwood:
Brushing
Use a high-quality natural bristle brush to work the finish into the wood grain. Ideal for smaller projects. Provides good penetration.
Rolling
A roller with a 1/4″ – 1/2″ nap quickly and evenly applies finishes to larger flat surfaces like siding and fences. Use a brush on edges and joints.
Spraying
Airless spray systems allow finishing large areas efficiently. Provide an even coat and professional results. Requires masking off other areas.
Wiping/Rubbing
Wipe on oils using a clean, lint-free cloth. Rub in multiple thin coats until wood is saturated. Quick and simple for small projects.
Applying the Finish Correctly
Follow product directions closely and use proper techniques for best results:
Stirring
Stir finishes thoroughly before and during application to maintain even consistency.
Thinning
Only thin products specifically designed to be thinned. Follow label directions carefully.
Coats
Apply multiple thin, even coats for best protection. Lightly sand between coats.
Brush Strokes
Brush along the wood grain to spread finishes smoothly and evenly. Avoid excess overlapping.
Dry Time
Allow finishes to dry completely between coats as directed by labels. Cool temperatures or high humidity can prolong drying.
Protection
Wear gloves, eye protection, and work clothes to avoid skin exposure when applying finishes.
Maintaining and Renewing Outdoor Redwood Finishes
Regular maintenance ensures lasting beauty and protection:
Inspections
Inspect redwood finishes twice a year for wear, damage, or failure. Address any issues immediately to prevent costly repairs later.
Washing
Clean finished surfaces annually with a brush and mild cleaner to remove dirt and mildew that can damage the finish. Avoid power washing.
Spot Repairs
Sand affected areas to remove failing finish, then spot apply a fresh coat to blend repair into surrounding finish.
Complete Refinishing
When coatings show extensive wear, completely strip redwood down to bare wood using a chemical stripper or media blaster. Rinish following all preparation and application steps.
Removal
If desired, finishes can be completely removed with chemical strippers or media blasting. Allow wood to dry thoroughly before recoating or leaving unfinished.
Proper preparation, application, and maintenance of exterior wood finishes allow redwood to retain its natural beauty while resisting weathering and environmental damage. Always read and follow label directions closely when applying any finish product to achieve the best performance. With the right protective coating, redwood can provide many years of service and enjoyment outdoors.
Frequently Asked Questions About Treating Redwood for Outdoor Use
Treating outdoor redwood properly ensures its beauty and performance will endure. Here are answers to some of the most common questions about preparing and finishing redwood for exterior applications:
What are the best finishes for outdoor redwood?
The best choices are penetrating oils and sealants specifically formulated for exterior wood like redwood. Look for weatherproof finishes containing UV blockers, water repellents, and mildew inhibitors.
How often should I apply finish to outdoor redwood?
This depends on the product, but expect to reapply oils every 1-2 years and sealants every 2-4 years in harsh climates. Frequent light maintenance coats are better than allowing heavy wear then complete refinishing.
Does new redwood need to be finished?
Yes. While new redwood contains natural oils, it still requires additional protection when used outdoors. Apply finishes as soon as possible during or after installation.
Should I use a clear or colored finish on my outdoor redwood?
This depends on personal preference. Clear finishes highlight the wood’s natural beauty but require more frequent maintenance. Pigmented finishes provide extra protection but hide the grain.
What preparation is required before finishing outdoor redwood?
Always clean, lightly sand, and allow redwood to dry adequately before applying finishes. Repair any cracks, holes, or defects prior to coating for best results.
Can I apply water-based finishes over oil-based coatings?
No. You must completely remove old oil-based finishes before applying a water-based product. Never apply water over oil sealants.
How long does it take for finishes to dry on exterior redwood?
Drying times vary based on temperature, humidity, ventilation, and product. Most finishes become tack-free within a few hours but may take 24-48 hours to fully cure.
What is the best application method for finishing outdoor redwood?
Brushing allows the finish to penetrate the wood grain, while spraying provides an efficient and even coat on flat surfaces. Always back-brush after spraying.
How do I maintain redwood finishes outdoors?
Inspect coatings twice yearly, wash annually, perform spot repairs promptly, and completely reapply finishes every few years to keep redwood protected.
Conclusion
Redwood’s natural beauty, strength, and resistance to insects and decay make it a cherished wood for outdoor structures, furniture, decks, and more. While redwood has some natural durability, applying exterior wood finishes protects it from constant exposure to sun, rain, snow, and other elements. The proper preparation, application, and maintenance of these protective coatings help redwood withstand decades of use outside. With a sound approach to treating and refreshing redwood finishes, projects will retain both structural integrity and aesthetic appeal over their lifetimes. Trust this comprehensive guide when selecting, applying, and caring for redwood finishes to unlock the full potential of this exceptional wood in any outdoor application.