What grout width do Ottawa tilers recommend for large-format rectified porcelain tiles?

For large-format rectified porcelain tiles, most experienced Ottawa tilers recommend a grout joint width of 1.5 to 2 millimetres (approximately one-sixteenth of an inch). Rectified tiles are precision-cut after firing so their edges are perfectly straight and uniform, which allows for these minimal grout joints that create a sleek, nearly seamless appearance.

That said, the practical minimum depends on the tile size and the realities of installation. For tiles in the 24-by-24-inch range, a 1.5-millimetre joint is achievable with a skilled installer on a properly leveled substrate. For very large format tiles — 24 by 48 inches or larger — many Ottawa professionals prefer a 2-millimetre joint as a practical minimum. The reason is that even small variations in substrate flatness or tile flatness become more pronounced at larger sizes, and a slightly wider joint provides a small margin to accommodate these without creating visible lippage (where one tile edge sits higher than its neighbour).

Substrate flatness is the single biggest factor in achieving tight grout joints with large-format tile. The industry standard is 3 millimetres of variation over 3 metres, but for large-format rectified tile with minimal grout joints, many installers aim for even tighter tolerances — 1.5 to 2 millimetres over 3 metres. In Ottawa homes with plywood subfloors, this almost always requires a self-leveling compound or careful substrate preparation before tile installation begins. Skipping this step and trying to set large-format tile on an uneven floor is the root cause of most lippage problems.

A tile leveling system (clip-and-wedge systems like Levtec, Raimondi, or similar) is essentially mandatory for large-format tile installation in Ottawa. These systems pull adjacent tiles flush during thinset curing and compensate for minor substrate irregularities. Combined with proper back-buttering — thinset applied to both the substrate and the back of each tile to achieve full coverage — a leveling system allows skilled installers to achieve the tight, uniform joints that make rectified porcelain look its best.

For grout type in narrow joints, use unsanded cementitious grout or a specially formulated grout designed for joints under 3 millimetres. Sanded grout is too coarse for these narrow joints — the sand particles will not fit properly and the grout will be difficult to pack into tight spaces. Many Ottawa tile professionals prefer epoxy grout for minimal joints because it flows into narrow spaces more easily and provides a harder, more uniform finish.

One practical note: while the ultra-minimal grout look is popular, going too narrow — under 1 millimetre — creates problems. Grout joints serve a functional purpose beyond aesthetics. They allow for minor thermal expansion, accommodate slight substrate movement, and provide a buffer between tiles. Ottawa's seasonal temperature and humidity swings make these expansion allowances more important than in milder climates.

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