I have installed a new balustrade for my stair and the half wall it is attached to is not straight. Leading up from the floor, it curves away from the wood so that it is about a 3/8" gap at the top - see image below. The half wall is USA 2x4 / drywall construction.

Please can anyone suggest the best way to close the gap?

Thanks in advance.

wall gap

  • So you are sure it is the wall that is not plumb? What are those black things between the wood and the wall? Aug 7, 2016 at 19:40
  • Hi Jimmy! I checked the wall with a spirit level, and yes, the wall is sadly not plumb. Those "black things" are wood shims to stop the wooden plank from bending.
    – Simon P
    Aug 7, 2016 at 20:16

3 Answers 3


Just wrap a small encasement around the board and last couple inches of wall. Three boards finished to match the rails. I doubt you would even need to do 45s, just drop the side boards from the top board by cutting it longer than the wall is wide/thick by twice the thickness of a side board.

  • I agree with this solution, just cover the gap with matching wood. Looks like you could use some thin oak panel, veneer, or plywood. Aug 7, 2016 at 22:50

In the end, I used joint compound to build out the gap.

I used wood shims to create a backing and set a depth for the fill. To avoid compound sticking to the wood and to also give a small shadow gap, I added strips of cardboard wrapped in plastic from a cut up letter file. Next, the 3/8" gap was filled with joint compound and left to dry for 24+ hours. Careful sanding allowed me to merge the fill with the existing wall. A bevel was created by even more gentle sanding after the protective pieces were removed.

Here is a photo just after surface sanding showing my setup: In Progress...

After a good lick of primer and paint, a capping wooden piece is installed on top of the half wall. The joint compound fill looks just like the rest of the wall. The result is good enough for my purposes!

Just be sure to let the joint compound dry fully before sanding (dry time may be extended because of the thickness).

  • That's what I was going to suggest doing. You should mark this as the answer. Apr 6, 2017 at 5:46

If it was me I would've built the end cap of the wall out and then refinished it. I can'tell really tell by the picture for certain that my suggestion will work. Anything else you try to do to it will be very noticeable.

  • Thanks for your reply! The balustrade is just screwed down, so it is possible to uninstall it as a last resort.
    – Simon P
    Aug 7, 2016 at 20:18

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