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d_kipp 05-02-2012 02:24 PM

Replacing 2x4 Rail Cap and Covering 4x4 Posts
I built our deck about 6 years ago - I used 2x4 (not pressure treated) railing caps over top of a fairly standard looking 2x4 top rail with wood ballusters. Now, the 2x4 rail cap is warping (not surprising) so I want to replace it with a 2x6 rail cap. Any advice or surprises that I should be aware of - or is it a fairly straightforward project?

Also, to attach the rail cap to the 2x4 top rail, will nailing from the top be appropriate or are there other recommended methods? Previously, I toenailed the 2x4 at the ends and glued the middle along with a couple of toenails in the middle. This obviously wasn't suitable to prevent warping.

One other unrelated question:
The 4x4 posts I used on the deck were pressure treated; as such, they show the typical little groove marks familiar with pressure treated 4x4s. I'd like to consider hiding these posts behind some sort of thin piece of wood on all 4 sides. If I use something like a 1x6 and cut it down to the width of the 4x4, mitering the sides to facilitate the wrap-around look, would this seem to do the trick? Any other suggestions or recommendations? I just don't like looking at the pressure treated 4x4s any more.

joecaption 05-02-2012 07:15 PM

Post a picture.
I would use slip on vinyl post covers, A post cap. and use composite decking material not a 2 X 6.
2 X 6's will cup, split, warp and splinter up in a few years,
I use A Kreg tool in the horizontal 2 X 4 under the top piece and install the screws from the bottom so no screws show.

d_kipp 05-03-2012 09:19 AM

Thanks Joe. Would the composite deck material as the rail cap look odd since the rest of the deck is wood? Or would the contrast actually add some style to the design?

I currently have post caps (wood) on top of the 4x4s but I want to saw off the top 6 inches to make the rail cap flat across the entire length - just a simple aesthetic change for something a little different. Plus, we have a mesh cabana sitting on the deck and the mesh tears when it gets snagged on the post caps in the wind.

Sorry - I don't have a picture of the deck handy.

joecaption 05-03-2012 09:33 AM

I've done many pressure treated decks with the composite decking as the top rail cap and my customers love then.
I've never once seen a pressure treated 2 X 6 laying flat like that not cup, splinter or crack.
We use a self leveling lazer level when cutting all the post to height, but a simple water level will also work. Clear plastic hose with water in it. Water seeks it's own level.

d_kipp 05-03-2012 09:55 AM

Thanks again - I'll take a look at some composite options for the rail cap.

Not my pics but here's what we intend to do:

Go from overheight 4x4 posts with post caps:
(image courtesy of

To a continuous rail cap without post caps:
(image courtesy of

Similar to the 2nd picture, our 4x4 posts are pressure treated with the little grooves - we want to hide these (I'll see if I can find some vinyl post covers in our city).

joecaption 05-03-2012 11:01 AM

Lowes and HD have them. Make sure to check before leaving the store to see if they will be big enough to slip over the post you have now.
Not sure why but some I picked up were 1/4" to small to fit any 4 X 4 I've seen.

d_kipp 05-03-2012 02:33 PM

Any chance you have pictures showing the wood deck with composite rail cap? I'm curious as to how contrasting it looks. Plus, it will help me determine how dark to go with the composite to make it look best.

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