How long to acclimate hardwood in the GTA

Acclimation is not a waiting room

Boards sitting in a sealed carton in a garage in February are not acclimating. They are cold. Material has to sit in the finished conditions of the room it will occupy — heat on, at the humidity the house will actually run at — with the cartons open or cross-stacked so air reaches every face.

Five days is a folk number. It comes from a world of narrow strip red oak delivered from a local mill in the same climate. It is not a specification and it is not a defence when a floor cups.

What is actually being matched

The target is moisture content equilibrium, not elapsed time. Solid hardwood in most of southern Ontario settles somewhere around 6 to 9 percent moisture content in service. The board arriving from the mill may be at 7 percent or at 11, and the subfloor it is going onto has its own reading.

The test is the difference. For narrow strip, a gap of more than about 2 percent between flooring and subfloor means movement after installation. For wide plank the tolerance tightens to roughly 1 percent, because a 7-inch board expresses the same percentage change across four times the width of a 1.75-inch strip.

That is why acclimation ends with a meter reading rather than with a date on the calendar, and why a delivery note that says the material sat on site for five days is not evidence that it was ready.

The Ontario problem specifically

A GTA house swings harder than the continental average. Interior relative humidity in a Toronto house in January, with forced air running and no humidifier, routinely sits in the low twenties. The same house in August, unconditioned, can be over sixty. That is a wider annual range than most flooring is engineered to be indifferent to.

It means a July install and a January install of the same floor are genuinely different jobs. Material delivered in July into an unconditioned house is at the wet end of its year and will shrink; the gaps show up in February. Material delivered in January into a dry house is at the dry end and will expand; the cupping shows up in July.

The correct response is to install to the middle of the house's actual range, not to the condition on the day. That requires knowing the range, which requires asking whether there is a humidifier and whether it gets used.

What we do on site

Deliver into the finished space, not the garage and not the basement. Heat or air conditioning running and stabilised — a house still being drywalled is not at its service condition. Meter the flooring and the subfloor, write both numbers down, and install when they converge rather than when the week is up.

If the readings will not converge because the house cannot hold a stable condition yet, the honest answer is to reschedule. A floor installed to a temporary condition is a floor installed wrong.

What it means for your schedule

Plan for material on site before the install window, in a room that is finished enough to hold temperature. If the trades are still working wet — drywall mud, paint, self-levelling compound — the wood should not be in the building at all. Wet trades are a humidity source and hardwood is a sponge with a finish on it.