Q. What do you think about using balau wood for outdoor furniture? Any comments are appreciated, as information on this wood is quite limited.
A: Balau wood is primarily Shorea glauca, S. laevis, S. albida, S. seminis, S. maxwelliana, S. astylosa. (Special note: The name "balau" is also used for some species of hopea...you do not want this wood.) The balau group in the Shorea genus consists of the strongest and densest species of Shorea. As such, balau is comparable to or exceeds many properties and characteristics of American white oak. Incidentally, Philippine mahogany is another common name used for some of the Shorea species, but the wood of such species is considerably softer and not suitable for outdoor use.
When handling this wood, you should absolutely make sure that all screw and nail holes are pre-bored. Otherwise, you are likely to find some small splits that will grow with repeated wetting and drying. In fact, I suggest that you only use bolts (no screws or nails, even when holes are pre-bored) for fastening wood used for outdoor exposure due to the splitting risk.
The high density of the wood means rapid dulling of tools. Gluing must be done immediately after surface preparation to avoid the movement of oils to the surface, which will prevent good adhesion.
The wood is very heavy. As a general rule, heavy, dense species have a tendency to split when exposed outdoors to rain and sun. You may find that the ends of pieces will split after exposure to rain and then drying. A good water resistant coating will be beneficial.
The wood has a good life expectancy when used above ground that is, the heartwood has fairly good natural resistance to decay and most insects. Although it is not as good as teak, it is often used and sold as asubstitute, as balau is quite a bit cheaper.