The use of tropical hardwoods on outdoor decks and stairs has increased dramatically in the last 15 years. There has been a corresponding increase in the demand for new deck coating products that are suited for use on these woods.
We at John Grey Painting have tried various products with somewhat mixed results. The great number of species of hardwood (Ipê is probably the most commonly used, but greenheart, cumaru, jarrah (a sub-tropical species from Australia), ekki (bangassi, azobe), apitong, mahogany, pao lope, teak and a few others are used for decking as well.) make product selection a bit difficult. There also is a divergence of theory regarding the issue of whether very dense hardwoods should be coated at all.
We have concluded that the only need for coating is primarily an aesthetic one (to remove the gray weathered look which obscures the color of the grain) but also may help reduce the prevalence of mildew and mold.
There are a couple of products we use with good results. One is water born acrylic and one is penetrating oil.
Cleaning and sealing every few years will help maintain a fresh new look on your decks.