How to Paint Expansion Joints

Yesterday I shared with you how to deal with tricky ceiling angles and proper colour placement. The same interior paint job happened to also provide me with the opportunity to share another colour placement dilemma that I often see handled the wrong way.


Expansion Joints

If you are unfamiliar with the term, expansion joints (or control joints) are installed between two pieces of drywall to deal with areas, where if they were only taped and mudded, would likely crack under foundation settling or structural shifting. You find expansion joints most often on large walls or large open rooms with high ceilings. You also see them in stairways. In residential construction, expansion joints are mostly covered with trim boards.

The dilemma in painting is whether those boards covering expansion joints considered wall or trim? And how to you paint them?

The answer is – it depends.

Sorry. But it really does.

It depends on a couple of things. Mostly it depends on what the expansion joint is connected to.

In the case of the last interior paint job we did, there was a large expansion joint on the open wall. It went corner to corner across the wall. We painted it out in the wall colour. Why? Because it didn’t butt up against any other trim. Treating it as trim would have created a line, breaking the large wall in two. There was no reason to do this.

So when should you treat an expansion joint as part of the trim?

When the expansion joint becomes part of baseboards or other trim. This happens mostly on staircases. It is exactly what I have on my staircase so I treated it like trim. When we first bought our house the expansion joint was a 2 1/2 inch wide board and it looked out of place. When we replaced our baseboards, I had our carpenter replace these boards to match our baseboards so I have a seamless transition.

Here is another example of when you are going to treat an expansion joint as trim.

You want to make sure the expansion joint board is substantial enough to warrant being treated as trim. I see lots of expansion joints that are covered with 2 1/2 or 3 inch boards and it ends up looking like a really high chair rail.

So to recap on how to treat expansion joints:

Treat like wall and paint it wall colour when

  • the expansion joint is corner to corner on a large wall that isn’t connected to any other trim
  • you want to minimize the noticeability of the expansion joint
  • the expansion joint board is thin

Treat like trim and paint out in trim colour when

  • the expansion board butts into other trim such as baseboards on second floor, stair skirts or crown
  • the only way to switch the board from wall to trim would be to create a line with paint on the board (you never want to do this).
  • the trim board is big enough to standout as trim



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