What caulking goes on before Ottawa interior paint?

Caulking before interior paint is one of those steps that separates a professional-looking result from a DIY job that always looks slightly off. The short answer: paintable acrylic latex caulk is the right product for virtually all interior pre-paint applications in Ottawa homes, and it goes on after priming but before your finish coats.

The most common spots that need caulking before interior paint are the joints where trim meets wall (baseboards, door casings, window casings), inside corners where two walls meet, and any gaps where ceiling meets wall in older homes. Ottawa's extreme temperature cycling — from -25°C winters to +35°C summers — causes wood trim to expand and contract significantly over the years, which opens up these joints even in relatively newer homes. A clean bead of caulk fills those gaps and gives you crisp, shadow-free lines that look intentional rather than neglected.

For product selection, look for 100% acrylic latex caulk labelled "paintable" — DAP Alex Plus, GE Paintable Silicone, or similar products widely available at Home Depot or Rona in Ottawa. These typically cost $5 to $10 per tube and are easy to tool smooth with a wet finger. Avoid pure silicone caulk for painted surfaces — paint won't bond to it and you'll end up with peeling lines within a year. The hybrid "siliconized acrylic" products are fine for most applications and offer slightly better flexibility, which is useful given Ottawa's humidity swings between bone-dry February air (sometimes below 20% RH with forced-air heat) and humid July conditions.

The critical technique point: caulk must be fully dry before you paint over it. Most acrylic latex caulk is paintable in 30 to 60 minutes under normal conditions, but in a cold Ottawa basement or a poorly heated space in winter, give it two hours minimum. Painting over wet caulk causes it to wrinkle and crack as it cures under the paint film.

One common pitfall — don't caulk the bottom of baseboards where they meet the floor. That joint needs to breathe and move, and caulking it traps moisture and tends to peel away within a season. Save the caulk for the top edge where baseboard meets drywall.

For a single room this is very manageable as a DIY step. For a full house repaint where you want truly sharp lines throughout, a professional painter will typically include caulking as part of their prep — and it's worth confirming that's in the scope before you sign off on any quote.