Thermo Merbau

Already very durable. Modified for different reasons.

Intsia bijuga — merbau, kwila in the Pacific trade — is a dense Southeast Asian hardwood that rates EN 350 class 1–2 in its raw state. It does not need thermowood to survive outdoors. It needs it for two other problems every merbau installer knows.

First, movement: dense tropical hardwoods swing with Indian humidity cycles, and a merbau deck laid tight in the dry season opens gaps by monsoon end. The 212°C cycle drops equilibrium moisture to 4–6% and halves that movement. Second, bleed: raw merbau leaches a red-brown extractive that stains tiles, render and pool surrounds for its first seasons outdoors — the species' best-known defect. Thermal modification destroys and fixes much of that water-soluble extractive load, sharply reducing bleed. The board that comes out is calmer, darker, and kinder to whatever sits below it.