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Technical paper · v1.0

Climate Mastery

Why hardwood succeeds or fails in Toronto

Toronto's indoor relative humidity swings from the high teens in winter to above sixty percent in summer — one of the most aggressive annual ranges of any major North American residential market. This paper sets out what that does to wood, the measurements that have to happen before a single board is laid, and the failure modes that appear when any step is skipped.

Chart of Toronto indoor relative humidity across the year — winter falling to 18 to 25 percent, summer rising above 60 percent, with the 35 to 55 percent band that hardwood is stable in marked across the middle.
Climate mastery — Toronto's indoor air spends much of the year outside the band hardwood is stable in. Every moisture decision on this site exists because of this chart.View full size — Chart of Toronto indoor relative humidity across the year — winter falling to 18 to 25 percent, summer rising above 60 percent, with the 35 to 55 percent band that hardwood is stable in marked across the middle.
Published August 1, 202613 pages9 min readFor Homeowners, designers, general contractors, property managers

Toronto's climate reality

Wood is hygroscopic and anisotropic: it exchanges moisture with the surrounding air continuously, and it moves. Expansion and contraction occur primarily across the grain — length change is minimal, width change is significant and cumulative. Every board arrives with its own moisture history.

The question is never whether a floor will move. It is whether the floor was specified, tested, acclimated and installed to survive decades of that movement.

Indoor relative humidity across a Toronto year, with the winter low, the summer high and the band in which hardwood is dimensionally stable marked across the middle.
Toronto indoor air spends much of the year outside the range hardwood is stable in: 18–25% RH in deep winter, above 60% in summer, against a safe operating band of 35–55%. Every moisture decision on this site follows from this chart.View full size — Indoor relative humidity across a Toronto year, with the winter low, the summer high and the band in which hardwood is dimensionally stable marked across the middle.
Indoor relative humidity, Toronto residential
ConditionRelative humidity
Winter indoor low18–25% RH
Summer indoor highabove 60% RH
Safe operating band for hardwood35–55% RH

Moisture testing — the first non-negotiable

A floor installed over a wet subfloor, or with boards that have not equalized, will cup, crown, gap or buckle. There is no warranty language that can override physics.

The order moisture readings are taken — subfloor first, then the flooring material, then both written onto a record sheet.
The order is the point: the subfloor is read first, the material second, and both go in writing before any deposit changes hands. The acceptable difference between them is the manufacturer's and ours.View full size — The order moisture readings are taken — subfloor first, then the flooring material, then both written onto a record sheet.
  1. Subfloor moisture content must be measured.
  2. Flooring material moisture content must be measured.
  3. Both readings must sit within the manufacturer's and Ecowoods' acceptable delta.
  4. Testing occurs at the free estimate, and again immediately before installation.

Solid versus engineered in the GTA

Solid hardwood is typically 3/4" (19 mm) with a generational wear layer, highly sensitive to RH swings, and best over plywood with a nail-down installation.

Engineered hardwood pairs a real hardwood wear layer with a 90° cross-ply core. That construction is what gives it dimensional stability over concrete, in condominiums, and above radiant heat.

Correct method matched to substrate

Installation method is not a preference and not a sales option. It is determined by the substrate, the product construction, and the climate load the floor will face for decades.

Three floor assemblies cut open side by side, each pairing one substrate with the fastening method that is correct for it.
The substrate decides the method. Nail-down is for solid over plywood; glue-down for engineered over concrete or in a condominium; floating for engineered over radiant heat, or where acoustic separation is required.View full size — Three floor assemblies cut open side by side, each pairing one substrate with the fastening method that is correct for it.
MethodWhen it is correct
Nail-downSolid hardwood over plywood
Glue-downEngineered over concrete, or in condominiums
FloatingEngineered over radiant, or where acoustic separation is required

The Ecowoods non-negotiable protocol

These steps prevent physical failure, and they are what make a lifetime workmanship warranty something a company can offer and still sleep at night.

The installation protocol drawn as a row of gates, each one a point where work stops until a condition has been met.
The protocol is a series of gates rather than a checklist — work does not proceed past one until its condition is met. Moisture testing is the first gate, and it sits before any deposit.View full size — The installation protocol drawn as a row of gates, each one a point where work stops until a condition has been met.
  1. Moisture testing of subfloor and material, documented.
  2. Minimum 72-hour acclimation in the actual conditioned space.
  3. Correct installation method matched to substrate.
  4. Proper expansion gaps at all fixed objects and walls.
  5. HEPA dust containment throughout the process.

What happens when a step is skipped

These are not aesthetic issues. They are permanent, visible records of process failure that no amount of later refinishing can fully erase.

One skipped moisture step on the left branching into the five named failure modes on the right — cupping, crowning, gapping, buckling and edge peaking.
The five failure modes are not five separate risks. They are five outcomes of the same omission, and which one appears depends on where the moisture came from and when.View full size — One skipped moisture step on the left branching into the five named failure modes on the right — cupping, crowning, gapping, buckling and edge peaking.
  • Cupping — edges higher than the centre of the board
  • Crowning — centre higher than the edges
  • Seasonal gapping
  • Buckling and tenting
  • Edge peaking and finish failure

What an informed homeowner should demand

Any company that cannot or will not provide these is optimizing for speed and lowest bid, not for decades of performance.

  1. Written moisture readings of both subfloor and material before any deposit.
  2. Explicit confirmation of minimum 72-hour acclimation in the actual space.
  3. A fixed price in writing, with no open-ended "unforeseen conditions" language.
  4. Confirmation that salaried artisans, not subcontractors, will perform the work.
  5. Lifetime workmanship warranty language in the contract.
  6. Willingness to refuse the job if conditions are wrong.

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