Sagging hand rails

Our new (to us) house has a Trex deck, with Trex 4x4 posts and Trex handrail on top. (Below it are cable railing “wire railing” horizontals.) Because of the view we want to keep the cable railings, but the topmost rail (Trex) is sagging between every post, plus or minus 1/4”, which is quite noticeable.

My first thought was to replace the entire rail system, but I’ve abandoned that in favor of just getting rid of the sagging top rail. It, however, is “supported” (not well, obviously) by another piece of Trex at 90 degrees forming a “T”. Trex wiggles and wobbles a lot more than lumber, at least in my experience, and in the 8 years since this was installed the deck rail is sagging, as is the “supporting” T piece, which is about 3” wide by the usual Trex thickness. It’s not enough. It’s like it has melted in the middle between every post or something.

My plan is to sister some PT pine to the sagging member on both sides, then the Trex T piece can sag all it wants, the lumber will be fastened only at the end point near the post(s) so it won’t be dragged down. Then I will top those sistered pieces with some 1x oak or cedar or whatever as the top rail and go on my merry way. If it matters the posts are roughly 6’ apart. Everything is code.

I would take the entire top off but that doesn’t seem possible because the vertical member is actually cut into the posts and taking it out would leave gaping wounds. Speaking of, the top piece (railing) of Trex is nailed into the top of each post, and I can’t “unscrew” it or otherwise dislodge it easily. I don’t care what condition it comes out in, but I don’t want to wreck the posts by sledgehammering it off, I’m afraid to take a sawzall to the underside for fear of btchng up the post, etc. The nails are well countersunk, large finish nails so far as I can tell, so very little head to grab on to.\

Suggestions for removing the top rail? How would you do it? Dig out the nails with a bear claw? Sawzall from under? Just beat the crap out of it until there’s enough space for a crowbar? Other solutions?

When I look at the Trex website, it looks like its made of particle board.

That is my experience with book cases made of particle board. They sag under weight.

Yes, reinforcing with something should help.

During one of my poverty periods, I build some “furniture” with plywood that sagged. To correct that problem, I purchases a length of 1 or 1.25 inch square tubing. Bored some holes in the tubing and bolted the tubing to the underside of the plywood shelf/top. Solved my problem. You might find the visual effect more bothersome. Angle bracket might work as well.

Hi Goofyhoofy,

Finishing nails?

Many years ago, I watch someone disassembling some walnut carvings on a staircase. They were fastened with brads. The wood underneath had some rot problems and he wanted to restore it.

He very carefully drilled the head of each brad. This left a relatively smooth shank and he was able to remove all the pieces.

He was very careful, using a small bit and took his time.

Of course, the idea was to preserve the pieces.

If you are not going to preserve what you are removing, a larger bit might work.

The bit needs something to center into.

Does that help you?

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I’m not sure how you could apply this to your situation, but if you want a horizontal piece of lumber to never sag use galvanized flashing sandwiched between two layers of lumber.

Take 1 of the pieces of lumber and elevate it on a step or block of wood. Have somebody step in the middle of the lumber, bowing it down as far as possible. Take a piece of galvanized flashing and nail each end to the ends of the bowed piece of lumber. Pull it as tight as you can. When the person steps off of the bowed piece of lumber it will stretch the piece of galvanized tight. Nail the second piece of lumber over the galvanized. This produces a very ridged beam. I’ve never have had one fail yet.


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Since you don’t care about saving the Trex, grind the heads off the nails with a Makita grinder.

I’d cut a 4x4 post to 40.5 inches and nail a piece of 2x4 to the end of it… and use that with my 24" crow bar to pry up the the trex rail.

While you’re doing that, I’ll be cleaning the mildew stain off my 35’ of redwood top rail with a light bleach solution, and then ponder the next step… applying something to prevent it from mildewing again so quickly.

As it is we can’t lean on it at sunset without getting black sleeves.


Speaking of, the top piece (railing) of Trex is nailed into the top of each post, and I can’t “unscrew” it or otherwise dislodge it easily.

The nails are well countersunk, large finish nails so far as I can tell, so very little head to grab on to.

An even larger finish nail, with the point ground off, could be used as a big nail set to drive the existing nail all the way through the top rail.

Hollow screw extractors could be used to remove the wood around the head of the finish nail until a vise-grip can grab it, then the vise-grip provide a basis for levering it out with a wonder bar.

…Trex handrail on top.
… but the topmost rail (Trex) is sagging between every post, plus or minus 1/4”, which is quite noticeable.

It sounds like the top rail is made - improvised - from Trex decking. On their web site the only railing system I found was made of aluminum.


Trex requires more support than wood. We recently had deck stairs replaced, and while we were at it the contractor suggested we have a third stringer put in the middle of the other two in case we choose to switch to Trex or some other composite when we need to replace the decking. We were told the stairs was the one place that did not have close enough support for composite decking.

I don’t think I’ve ever seen Trex rails. Usually plastic or metal. I realize this doesn’t help you now but it may help someone looking to put in a deck.


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I don’t think I’ve ever seen Trex rail

Neither have I, and I suspect this is why. I’d bet this was a “getaway” job for a not great contractor: looked good until the check cleared, then began to sag.

So that’s an exaggeration, but the previous homeowner said she had the deck rebuilt in 2014. On the underside I see that the joists are 12” on center, and every other one is new and has a metal joist hanger, the older ones do not. So they added structure because the Trex bounces, and chopped a Trex board in half and used it to support the rail. But it doesn’t.

So I’m a gonna fix. Next project after I get the awning railings up on the roof. Hate doing springtime chores in the summer, but I’m always a little behind.

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