Timber is a natural, renewable material, easy to fabricate, and with low-carbon emissions. As a construction material, however, when put under enough directional force along its grain, sawn timber is structurally unstable, so deemed unsuitable under higher loads. In comparison, the manufacture of cross-laminated timber (CLT) involves simply gluing multiple layers of timber together at right angles. By crossing the direction of the grains, CLT achieves a far higher level of structural rigidity along both axes. CLT boards start with a minimum of three layers but can be strengthened further with the addition of more. Simply put, due to the complex physics involved in the perpendicular lamination, the strength of CLT board is similar to that of reinforced concrete, and has proven performance under seismic forces.