Add Post Caps and Trim
Decorative post caps protect the vulnerable end grain of your posts while adding a polished, finished look. Choose from flat, pyramid, copper, or solar light styles to match your deck aesthetic.
Quick Summary
30-60 minutes
$5-$50 per cap
Easy
High visual appeal
Why Post Caps Matter
Post caps serve both aesthetic and practical purposes. Without caps, the exposed end grain on top of posts acts like a sponge, absorbing rainwater and accelerating rot. Caps shed water away and protect this vulnerable surface. They also hide any imperfect cuts and give your deck a polished, intentional look that says "finished project" rather than "work in progress."
The End Grain Problem
Wood end grain absorbs water 10-15 times faster than face grain. When water sits on an unprotected post top, it soaks deep into the wood, causing splits, cracks, and rot from the inside out. A simple cap can add years to your post life.
Post Cap Styles
Flat Caps
$5-$10 eachSimple, low-profile design that covers the post top. Clean, modern look that doesn't draw attention. Available in wood, composite, or metal. Good choice for minimalist designs.
Best for: Modern decks, clean lines, budget-friendly projects
Pyramid Caps
$8-$15 eachClassic pointed design that sheds water effectively. Traditional appearance that suits most deck styles. Available in wood, composite, vinyl, and metal finishes.
Best for: Traditional decks, craftsman style, colonial homes
Ball-Top Caps
$15-$30 eachDecorative sphere or acorn finial adds elegance. More ornate option for formal outdoor spaces. Often available in turned wood or metal.
Best for: Victorian style, formal gardens, upscale designs
Copper Caps
$20-$50 eachPremium look that develops beautiful patina over time. Excellent durability and weather resistance. Starts bright and gradually turns to verdigris green.
Best for: Coastal homes, Craftsman style, premium projects
Solar Light Caps
$15-$50 eachBuilt-in solar panel and LED light. Charges during the day, automatically lights at dusk. Provides ambient lighting without wiring. Lasts 6-8 hours per charge.
Best for: Evening entertaining, stair safety, ambiance
Measuring for Post Caps
Post caps are sized by nominal lumber dimensions, not actual measurements:
4x4 Posts
Nominal: 4" x 4"
Actual: 3.5" x 3.5"
Use 4x4 post caps
6x6 Posts
Nominal: 6" x 6"
Actual: 5.5" x 5.5"
Use 6x6 post caps
Pro tip: If you've wrapped your posts with post sleeves or trim, measure the actual outer dimensions. Sleeve-style caps fit over the post rather than sitting on top.
Installation Steps
Prepare the Post Top
Ensure post tops are clean, dry, and level. Sand any rough spots or raised grain. If posts were stained, make sure they're fully cured. Wipe away any dust or debris that could prevent adhesion.
Test Fit Each Cap
Before applying adhesive, place each cap on its post to check fit. The cap should sit level and have a small overhang (the skirt) that covers the post edges. Make sure the fit is snug but not forced.
Apply Construction Adhesive
Apply a bead of outdoor construction adhesive around the inside of the cap's skirt, or apply to the post top in an X pattern. Use adhesive rated for outdoor use and your cap material (wood, composite, or metal).
Install and Level
Press the cap firmly onto the post. Check with a level in both directions. Adjust as needed before adhesive sets. Wipe away any excess adhesive that squeezes out. Allow to cure per adhesive instructions.
Solar Post Cap Tips
Getting the Most from Solar Caps
- Placement matters: Install on posts that receive direct sunlight for best charging
- Initial charge: Let new solar caps charge in sun for 24-48 hours before first use
- Keep clean: Wipe solar panels occasionally to maintain charging efficiency
- Battery replacement: Rechargeable batteries typically last 2-3 years and can be replaced
- Strategic placement: Prioritize stairs and elevation changes for safety lighting
Additional Trim Options
Post Skirts/Collars
Decorative trim at the base of posts where they meet the deck. Hides gaps and adds a finished look. Available in matching materials.
Post Wraps/Sleeves
Covers the entire post with a clean, uniform surface. Hides imperfections and provides a consistent look. Composite sleeves are low-maintenance.
Fascia Board Trim
Covers the rim joist for a polished edge. Matches decking material for cohesive look. Protects framing from weather.
Rail Lighting Channels
Under-rail LED strips for ambient lighting. Many systems integrate with post caps for a coordinated lighting design.
Frequently Asked Questions
What size post cap do I need?
Post caps are sized by nominal lumber dimensions. A 4x4 post (which actually measures 3.5 x 3.5 inches) uses a 4x4 cap. A 6x6 post (actually 5.5 x 5.5 inches) uses a 6x6 cap. Measure your posts to confirm, especially if using sleeve-style caps that fit over the post.
How do I attach post caps?
Most post caps attach with construction adhesive. Apply a bead around the inside of the cap's skirt or on the post top, then press firmly. Some premium caps have screw holes for additional security. Solar caps may require drilling for wiring.
Are solar post caps worth it?
Solar post caps are an excellent investment for decks. They provide ambient lighting without electrical wiring, charge during the day, and automatically light up at dusk. Modern solar caps last 6-8 hours per charge and the LED bulbs last for years. They're especially valuable for marking stairs and railings.
Do post caps protect the wood?
Yes, post caps serve an important protective function. End grain on the top of posts absorbs water like a sponge, leading to rot and cracking. A cap sheds water away from this vulnerable surface, significantly extending post life. Even simple flat caps provide good protection.