As a natural material, timbers have slight variations in grain and color. Occasionally a crack, known as a "check", will appear on the surface of a timber. Checking does not compromise the strength of a timber; it's a naturally occurring feature that can happen when timbers contain heartwood (wood cut from the center of the tree). Checking can also occur if timber is allowed to dry too quickly. The surface of all wood will also darken with age. All wood treated with a clear finish will darken. You can expect the timbers exposed to daylight to darken slightly over time.