Our 1950s bungalow has original subfloor planks — is that stable enough for tile?

Original 1950s subfloor planks are typically not stable enough for tile installation without significant preparation. Most homes from that era have 1x6 or 1x8 diagonal planks that will move and flex too much for ceramic or porcelain tile.

Tile requires an extremely stable, rigid substrate to prevent cracking. Your original plank subfloor likely has some deflection (bounce) and the individual boards can shift slightly over time. Even small movements will telegraph through to the tile, causing cracks in grout lines or even the tiles themselves. The gaps between planks also create weak points that can lead to hollow spots under the tile.

The standard solution is adding a layer of plywood or cement board over your existing planks. Most contractors will install 5/8" or 3/4" plywood subflooring, screwed down every 6-8 inches to eliminate any movement. For wet areas like bathrooms, cement board or Hardiebacker over the plywood provides additional moisture protection and rigidity. This brings your subfloor up to modern standards while preserving the original structure.

In Ottawa's climate, moisture considerations are especially important with tile installations over wood subfloors. The temperature swings and humidity changes can cause wood movement, so proper vapor barriers and expansion joints become critical. Licensed contractors will also check that your floor joists can handle the additional weight of tile and substrate - 1950s construction was typically robust, but verification is important.

Before any tile work begins, have a professional assess your subfloor deflection using the proper span tables and deflection limits. They'll also check for any loose or damaged planks that need repair. For a free assessment of your subfloor and tile installation options, request a quote from Ottawa Floor Install.