The big decision is roll-in or low-curb. A roll-in shower has no threshold at all, so it works with a wheelchair or a shower commode chair. A low-curb shower keeps a small lip to hold water but is still easy to step over. If your parent uses a walker today, we'd lean toward roll-in, since needs tend to grow.
Markham houses bring their own puzzles. Older back-splits in Thornhill and Milliken often have a single tub-and-shower in a small bathroom, so a tub to walk-in shower conversion is common. Newer homes in Cornell and Berczy Village may have a main-floor powder room that can grow into a full accessible bathroom. In condo units, drain location and the floor slab limit how flush a roll-in can be, so get the building's input early.
Prioritise an installer who has done accessible bathrooms before, not just general tiling. Ask how they handle waterproofing and floor slope, where the grab bars will be anchored, and whether the shower valve has anti-scald protection and a hand-held head on a slide bar. Get a written quote, a timeline, and a warranty on both workmanship and waterproofing. If your parent will be living at home during the work, ask how long the bathroom will be out of use. Ask your accountant about the federal Home Accessibility Tax Credit for this work, and check with Veterans Affairs Canada if your parent served.
Our recommendation is a roll-in accessible shower with a fold-down seat for anyone with changing mobility. The trade-off is a longer and costlier job than a simple low-curb pan, especially in a small bathroom. Markham has few specialists, so families often compare installers in Richmond Hill, Scarborough and Vaughan as well.