The previous owner of our home had a shoddy job down on some stairs leading to a rec room carved out of some of the attic space. There are four stairs leading up to the room, and under each one is a gap about half an inch wide and deep. There are vertical gaps alongside the stairs, too, but nowhere near as bad. Here's a photo of all the stairs, with a closer look at a couple of the gaps further below:

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I'd like to fill in these gaps between the drywall under the stairs and the stairs themselves so that I can then paint over them to make it look much nicer, but I'm not sure what the best material would be to do that. I'm considering wood filler, joint compound, or a foam sealant such as Great Stuff. Would one of these be ideal for this job, or is there something else I should consider? Not having done a DIY project like this before, I don't know what material would be ideal for filling gaps between drywall and the wood planks that make up the stairs without too much worry of future cracking.

Here's a close-up of a couple of the stairs to give you a better idea of what the gaps are like:

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3 Answers 3


Absolutely do not use an expanding gap filler, it will make matters worse. If you have verified that each step is level so that it doesn't need to be re-secured to the tread than the gaps can be filled. Also verify that the steps are not loose or shifting.

The easiest and most used product to fill each gap would be a latex caulking. A cartridge (or tube) is placed in a caulking gun and applied in a continuous bead along the gap. Once the gap is covered press it into the gap with a putty knife. This will also flatten the caulking so that it conforms with the flat wall. A very damp rag will wipe up any wayward caulk that didn't get pushed into the gap.

It will take about 24 hours for the caulk to fully cure. It than can be painted if desired, but there are plenty of colors to choose from which may not make painting needed.

As been suggested by a prominent authority well versed in caulking and fully supported by myself, you must be sure to use a Latex-type caulk. Not to be confused with a 100% silicone or a urethane caulking. Latex is easier and more forgiving than the other types.

  • 1
    An additional note to OP is to check the caulk used to make sure it is a paintable type. It is easy to make a mistake to select the wrong one at the home supply store and end up with some silicon or other type caulk that ends up non-paintable.
    – Michael Karas
    Commented Jan 3, 2016 at 22:24
  • I know! But point about the possible mistake can be made...
    – Michael Karas
    Commented Jan 3, 2016 at 23:10
  • Suggestion added.
    – ojait
    Commented Jan 4, 2016 at 2:45
  • This sounds perfect, thanks! I know exactly how I'll proceed now.
    – Derek
    Commented Jan 5, 2016 at 17:53

Typically a riser bracket is used, it would help if the stair return was longer but a piece of lattice cut to follow the zig-zag of the stair may work too.

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EDIT 1-5-2016


Here is another angle....


  • Thanks, this sounds like a great suggestion if the stairs aren't finished yet. It's a bit beyond my capabilities for my situation, though, and would probably require me to tear out and redo the bit of drywall beneath the stairs, so I'm doing the latex caulk solution proposed by ojait instead.
    – Derek
    Commented Jan 5, 2016 at 17:52
  • The zig-zag lattice goes right over the drywall as long as it is flush and not beyond the end of the riser. I am adding a sketch on what I mean, it is a pretty simple detail
    – Jack
    Commented Jan 5, 2016 at 23:42
  • Jack, do you happen to have a link to a sample product like that? Searching for "stair lattice" or "zig-zag lattice" turns up nothing on the big hardware stores' sites. Thanks!
    – Derek
    Commented Jan 6, 2016 at 16:54
  • It is simply lattice, 1 3/8'X5/16" mitered at the inside and outside corners that you can get off the shelf of any big box store. Cut with a miter box and set in place with small brads. Zig zag is just a description I gave it because that is what it reminded me of
    – Jack
    Commented Jan 6, 2016 at 21:02

While you 'can' fill it with drywall mud, and mesh tape, I wouldn't recommend it either. The stair treads will likely move some as they are stepped on and would just crack the mud. Caulking will probably fix it, but you will likely still see the edge where the caulking meets the painted drywall as it's hard to feather it. And if you have a textured wall, the caulked areas will be smooth and not match. The best solution is to trim it out, but if you don't have the skills or tools you can probably do OK with the caulking.

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