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Deck Post Caps
Post caps for deck railing posts, stair posts and porch posts, in one-piece Miterless mahogany, solid copper, marine-grade stainless steel and black stainless steel. Every cap slips over the top of the post to keep rain out of the end grain. Sizes run from 4x4 to 8x8. Please measure your posts before you order.
Why deck posts need a cap
Every deck railing post, stair post and porch post ends in end grain, the cut ends of the wood fibers. End grain takes in water far faster than the sides of a post. Rain and snow that sit on a bare post top soak straight down into it, and that is where checking, splitting and rot usually start.
A deck post does more than finish the railing. It holds the railing up. A deck can cost anywhere from a couple of thousand dollars to tens of thousands, and a post that rots from the top weakens everything attached to it. A post cap is a small part of the deck, but it is the part that keeps water off the top of each post.
A deck post left without a cap, wet through the end grain after rain.
NO CAP
An uncapped deck post. The end grain has soaked, dried and split open.
NO CAP, YEARS LATER
A post top that has rotted from the end grain down.
Slip over, not sit on top
Some caps sit flat on top of the post and are nailed down. Water runs under a flat cap the same way it runs onto a bare post, so it does little to protect the wood. A cap that slips over the post covers the end grain and the top of all four sides, so water runs off and away.
Every cap on this page slips over the post. The metal caps have a 3/4" lip that wraps the top of the post. The Miterless wood caps are routed out underneath, so the post sits inside the cap.
Why most wood deck caps split at the corners
The underside of a typical five-piece wood cap, with the trim glued and stapled at the corners.
Most wood post caps sold for decks are built from five pieces: a top and four strips of trim, stapled and glued together at the corners. It is a fast, low-cost way to make a cap. Sun, rain and the wood swelling and shrinking each season work the glue and staples loose, and the corners open up. Once a corner opens, water gets in between the cap and the post, which is the problem the cap was meant to solve.
Some of these caps also have a thin metal or plastic top glued on, which can come loose the same way.
FIVE-PIECE CAP
A glued and stapled cap with its trim splitting away from the post.
MITERLESS CAP
A Pyramid Miterless Wood Post Cap: one piece of mahogany, with no corner joints.
One piece of kiln-dried mahogany
Our Miterless Wood Post Caps™ are shaped from a single block of mahogany, so there are no corner joints to come apart. Every one is kiln dried for at least 30 days and moisture tested before it ships, which helps it hold its shape outdoors. They are guaranteed for life never to split at the corners. Our owner has Miterless caps on his own house that have been outside for more than 15 years.
Because the wood is dry when it arrives, you can stain or paint it right away to match the deck, the railing or white trim on the house. Left unfinished, mahogany weathers to gray like other deck lumber. Learn more about how Miterless caps are made.
MITERLESS WOOD
Pyramid Miterless Wood Post Caps on a deck railing, painted white to match the posts.
COPPER-TOPPED WOOD
Miterless caps with copper tops on a stained deck.
PORCH STAIRS
Pyramid Miterless caps on porch stair posts.
DECK STAIRS
Copper-topped Miterless caps on a two-story deck stair.
TRADITIONAL
4x4 Traditional Pyramid Miterless caps on a deck railing.
Choosing a material for your deck
All four materials protect the post the same way. The choice comes down to the look of the deck and where it is.
| Material | Best for | How it ages |
|---|---|---|
| Miterless mahogany | Decks you want to stain or paint to match | Weathers to gray if left unfinished |
| Solid copper | A warm accent on wood decks and porch railings | Bright, then bronze, then brown. Can turn green in wet or coastal climates |
| Marine-grade stainless steel | Lakefront, coastal and dock decks | Stays bright and does not rust |
| Black stainless steel | Black metal railings and dark-stained decks | Powder coated with a UV-resistant finish to resist fading |
For a deck on the water, choose stainless steel. Our stainless steel caps are 316 marine-grade stainless, the same material used for boat cleats and boat railings, because it holds up to splashing salt water. It is the material we recommend for lakefront, ocean-side and dock decks.
Our black caps are 304 stainless steel rather than the aluminum most black caps are made of. Each one is sandblasted and cleaned before it is powder coated, so the coating bonds well and lasts.
Stainless steel caps on a lakefront deck.
You can also put metal on top of a wood cap. The West Indies Miterless Wood Post Cap™ comes with a copper, stainless steel or black stainless steel pyramid on a mahogany base.
WOOD
Miterless wood caps on a porch railing, finished to match the handrail.
STAINLESS STEEL
A stainless steel pyramid cap on a white deck railing.
Measure your deck posts before you order
"4x4" and "6x6" are the names of the posts, not their measurements. At the mill, a post is first cut to its full size, which leaves the surface rough. Most posts then go through a second set of cuts that smooths all four sides and takes off about half an inch. That smooth post is called a nominal post, and it is what lumberyards and home centers sell. A post that skips the second step is called rough cut, and it measures the full size.
| Post | Nominal (smooth) post measures | Rough-cut post measures |
|---|---|---|
| 4x4 | 3 1/2 x 3 1/2 in | 4 x 4 in |
| 4x6 | 3 1/2 x 5 1/2 in | 4 x 6 in |
| 6x6 | 5 1/2 x 5 1/2 in | 6 x 6 in |
| 8x8 | 7 1/2 x 7 1/2 in | 8 x 8 in |
On most decks the railing posts are 4x4s, and the posts that hold the deck up are often 6x6s, so one deck can need two sizes. Measure across the flat face at the top of each post, in both directions, and use the larger figure. If the posts are wrapped in vinyl or composite sleeves, measure the outside of the sleeve.
Sam Glasgow, our vice president of operations, estimates that five to eight percent of post cap orders are placed in the wrong size, almost always because the post was ordered by its name instead of measured. Our team screens orders and calls customers when a size looks wrong. If you are not sure, call us before you order.
How to install caps on deck posts
- Wood caps. Apply a generous amount of outdoor construction adhesive, such as Liquid Nails, to the top of the post and press the cap down over it. Wipe off any adhesive that squeezes out and runs down the post.
- West Indies caps with a metal pyramid. Glue the metal pyramid to the wood base first with the same adhesive and let it dry. Then glue the finished cap onto the post.
- Metal caps. Slip the cap over the post and drive the two included screws through the lip. Drilling a small pilot hole first makes the screws go in more easily.
Adhesive is sold separately.
STAIR RAILING
Wood caps on the posts of a deck stair railing.
WEST INDIES WITH COPPER
West Indies caps with copper pyramids along a deck railing.
Questions about deck post caps
Does every deck post need a cap?
Every post with an exposed top does. That includes the railing posts, the corner posts and the newel posts at the top and bottom of each stair.
Will a cap fit a post wrapped in a vinyl or composite sleeve?
Yes, if you measure the outside of the sleeve and choose the cap size from that figure.
Can I stain or paint a Miterless wood cap?
Yes. The mahogany is kiln dried, so it can be stained or painted as soon as it arrives.
Is there a warranty?
Yes. Our post caps are guaranteed for life never to split apart at the corners. If one does, we replace it with a product of equal value.
What if I order the wrong size?
Call or email us for a return authorization before sending anything back. New, unopened items can be returned within 30 days of delivery, with a 20% restocking charge unless the product is defective. Our Shipping & Returns page has the full details.
Not sure which cap is right?
Call us at 678-909-2720 with your post measurements and a description of your deck.
Shop deck post caps by size
| Post size | Wood | Copper | Stainless steel | Black |
|---|---|---|---|---|
| 4x4 | 4x4 wood | 4x4 copper | 4x4 stainless | 4x4 black |
| 4x6 | 4x6 wood | 4x6 copper | 4x6 stainless | 4x6 black |
| 5x5 | 5x5 wood | 5x5 copper | 5x5 stainless | — |
| 6x6 | 6x6 wood | 6x6 copper | 6x6 stainless | 6x6 black |
| 8x8 | — | 8x8 copper | 8x8 stainless | 8x8 black |
Building a dock? Round pilings take a round cap. See our round piling caps.