Flat grain is any wood board which was cut perpendicular to the natural growth lines of the parent tree. These woods are not as strong or stable as a vertical grain wood. Flat grain is the result of cutting parallel portions out of trees by sawing perpendicular to the natural tree growth lines. This approach isfrequently employed to make veneers. Wood cut in this manner has two sides, and these are the pith side and the bark side. The pith side is the portion closer to the center of the parent tree while the bark side is the portion of the cut wood close to the outer layer of the parent tree.

 

Flat grain wood is liable to changing and swelling with time. It is recommended by professionals to expose the flat grain wood's bark side as the pith side is more likely to experience grain separation. Saw texture can be used on the wood surface to minimize changes in the wood. Flat grain wood is often less expensive and more available than straight grain wood. It is however more vulnerable to damage and weathering which makes not as ideal for construction projects as vertical grain wood.