Sal Wood (Shorea robusta): Properties, Density & Uses

What Sal Is

Sal (Shorea robusta) is a large hardwood of the family Dipterocarpaceae, one of the most important structural timbers native to the Indian subcontinent 1. It is known regionally as sakhua, sarai and shala, and in some timber-trade classifications it is grouped commercially with the balau and red balau Shorea species 4. In its forests it is often gregarious and even dominant, forming stands where it is the leading species. For a buyer, the short version is that sal sits at the heavy, strong, durable end of the timber range — a working structural hardwood rather than a decorative or light-weight one.

Where It Grows

Sal is native to the Indian subcontinent and the lower Himalayan belt. Its range runs from the Shivalik hills in the north-west, across the Gangetic plain and central India — Odisha, Jharkhand, Chhattisgarh, Bengal and Assam — and extends into Nepal, Bhutan and Bangladesh, reaching east into Myanmar 1. It grows mostly below about 1,400 m. The tree is large, commonly 30–40 m tall and up to roughly 50 m on good sites, with a straight cylindrical bole clear for as much as 25 m and trunk diameters of 1–2 m 2. That long, straight stem is part of why sal has been a mainstay of heavy construction and railway supply for so long.

Appearance and Grain

The heartwood is dark reddish-brown and clearly demarcated from a thin whitish to pale sapwood 2. Freshly sawn wood is lighter and darkens on exposure, so colour deepens as boards weather. The grain is typically interlocked or strongly spiralled and the texture is coarse 3. Sal is also resinous, which lends worked surfaces a characteristic sheen but complicates a clean finish. In practical terms, it is a wood you specify for its strength and durability rather than for a smooth, furniture-grade face.

Weight, Density and Strength

Sal is a very heavy hardwood. At 12% moisture it dries to about 880 kg/m³ (55 lb/ft³), with reported air-dry figures ranging roughly 830 to over 1,000 kg/m³ depending on locality 3. Its Janka hardness is around 9,250 N (2,080 lbf), placing it firmly among the harder structural timbers 4. Bending strength (modulus of rupture) is broadly in the 95–130 MPa band air-dry, with an average near 110 MPa, and stiffness (modulus of elasticity) around 13–16 GPa 6. These figures vary with the source locality and the moisture at which the sample was tested, which is why ranges are more honest here than single numbers. To give a sense of scale, sal is roughly twice the density and about five times the Janka hardness of okoume — the light plywood-face species sits at one end of the range and sal at the other.

Working, Gluing and Finishing

Sal is hard, heavy and demanding to work 2. It saws reasonably but has a moderate to strong blunting effect on tools, and its high resin content makes planing, turning and polishing difficult, so surfaces rarely finish as cleanly as with lighter hardwoods 3. It splits readily when nailed, so pre-boring is advisable, and sharp carbide-tipped tooling helps offset the edge wear. It is also refractory to season — it needs slow, controlled drying to avoid checking and distortion, a consequence of its moderate-to-high shrinkage and a high tangential-to-radial ratio 2. None of this rules sal out; it simply means it rewards careful conversion and seasoning rather than fast handling.

Durability and Treatment

The heartwood is rated very durable and is highly resistant to termite attack and to fungal decay, which is precisely why sal has historically been used untreated for railway sleepers, posts and structural work 1. The narrow sapwood, however, is not durable and is prone to borer and insect attack, so for exposed applications the sapwood should be excluded or treated 3. Because the dense heartwood resists preservative uptake, the practical approach is to specify sound heartwood for exposed and load-bearing duty rather than to rely on treatment penetrating the wood.

Sustainability and Legality

Sal remains widely distributed and still common across its range, but the wild population is declining through habitat loss and fragmentation, which prompted the IUCN to up-list it to Near Threatened in its 2025 assessment, from an earlier rating of Least Concern 5. Much of the timber is harvested from government-managed forests in India and Nepal, where felling is regulated. Given tightening controls, buyers should seek legally sourced, permit-backed material and keep the supporting documentation on file.

How Cochin Wood Uses Sal

Cochin Wood Industries treats sal as a very heavy, strong Indian hardwood for structural, railway and heavy-duty work — the opposite end of the range from the light packing and Okoume plywood we manufacture. Where a project calls for genuine load-bearing timber — beams, posts, sleeper-grade or bridge and wagon work — sal's density and natural durability are the reason to choose it, and we source it as legally documented material to specification. For customers who need it as boards rather than panels, our sawn timber line covers heavy hardwood supply; you can compare it against other species in our wood encyclopedia, or see the complete range in the full catalogue. Tell us the section sizes, quantity and delivery location and we will quote against verified stock.