Wood Humidity & Temperature Guide

Wood is a hygroscopic material — it absorbs and releases moisture from the air, expanding and contracting as it does. Understanding the ideal conditions for your wood is the single most effective way to prevent cracking, warping, joint failure, and finish degradation.

Ideal Conditions by Application

Application	Ideal RH %	Ideal temp (°C)	Tolerance
Interior hardwood floors	45–55%	16–22°C	±5% RH; avoid rapid change
Period staircases & balustrades	45–60%	15–22°C	Joints tolerate slightly wider range
Solid timber furniture	45–55%	15–25°C	Narrow — movement causes veneer lifting
Wood panelling	50–60%	15–22°C	Allow for movement in fixing method
External window frames	—	—	Exposed to full range — finish integrity is critical
Wooden sculptures / turnings	45–55%	15–25°C	Avoid direct sunlight or heating vents

What Happens Outside Ideal Range

Condition	Effect on wood	Common signs
RH below 35%	Rapid moisture loss, shrinkage	Cracks along grain, gaps in floorboards, joint separation, veneer lifting
RH 35–44%	Mild drying, slight movement	Creaking floors, minor cracking at end-grain, finish crazing
RH 45–60%	Ideal — stable equilibrium	No movement issues
RH 60–70%	Mild swelling, some movement	Sticking doors and drawers, minor surface raised grain
RH above 70%	Significant swelling, mould risk	Sticking doors, buckling floors, mould growth on unfinished surfaces, rot initiation
Temperature below 10°C	Finish becomes brittle	Varnish cracking, oil not curing properly, finishes applying unevenly
Temperature above 30°C	Rapid moisture loss	Accelerated drying cracks; wax and oil soften on horizontal surfaces