HDU (High Density Urethane) signs last longer and require less annual maintenance than Redwood or Cedar signs. It is a rigid, closed-cell, lightweight formulation of urethane, and our HDU weighs 20 lbs per cubic foot, slightly lighter than Cedar wood. . It is completely waterproof.It can be sandblasted, routed, carved, sanded, or machined. It will not crack, twist or curl after long exterior exposure, making it the ideal replacement for wood signs.It is made specifically for the sign industry. There are three manufacturers in the USA, but we now use Precision Board Plus from Coastal Enterprises. Precision Board comes in sheets 5 ft wide and either 8, 10 or 12 ft long, which have thickness vary from 0.5 inch to 4 inches thick. HDU is lighter than wood, and a disadvantage is that it is not as rugged as wood and more susceptible to deliberate damage.
The advantages of Redwood and Cedar are the natural beauty of the wood grain when it is varnished or stained. This cannot be duplicated by HDU, although we can paint HDU so it looks like it has a wood grain. Wood is also more rugged, but does requires re-varnishing or re-painting every few years.Even then, it may split or crack, especially for large signs subject to freezing and thawing. Even though we use the finest all clear heart (no sapwood) kiln-dried Redwood and A-grade Cedar, , which is amazingly impervious to rot and splitting, it must be maintained through periodic painting or varnishing.
If you want a sign that is completely painted with oil enamels, we recommend HDU (Product Lines 1 and 2). If you want to stain or varnish your sign and give it a natural look, then should select Redwood ,  Cedar or Mahigany. Redwood has a more pronounced grain structure when sandblasted, so it has a more dramatic look. Cedar has less grain structure and sandblasted ridges are closer together. Both Redwood and Mahogany have less color variations, which is important for stained signs.