John asks: My local lumberyard stocks mahogany decking at a good price. How durable is this compared to other hardwoods? How would you recommend finishing?
Steve Bliss, of BuildingAdvisor.com, responds: Most wood decking sold in the U.S. as “mahogany” is actually dark red meranti or, in some cases, red balau. Meranti and balau are in the same family as lauan, also called Philippine mahogany.
Think of meranti as hardwood lite. It is popular because of its low cost, attractive color, and easy workability compared to ipe and other super-dense tropical hardwoods. However, don’t expect it to last as long as ipe or similar hardwoods.
Because of its appearance and marketing, Meranti is often confused with “real mahongany”, also called Honduran mahogany, South American mahogany, or True Mahogany. This is a different species with much better resistance against insects and decay. Most now comes from plantations in Peru or Central America. It is rarely sold as decking.
Meranti has the reddish appearance of a tropical hardwood, but its durability is more similar to softwoods. It has moderate resistance to decay and insects, similar to cedar and redwood, but is not much harder than yellow pine. It rates about 900 on the Janka scale, which measures wood hardness, compared to over 3,300 for ipe.
On the other hand, meranti is prone to split at end cuts if the end grain is not well-sealed. It is also more prone to general checking and cracking then denser hardwoods.
If you use meranti, make sure you seal the cut ends as soon as possible and get a good penetrating oil finish on all sides before installation – and before it has had a chance to weather and possibly start to crack.
As with any wood decking, maintenance and refinishing are important for longevity and appearance. If you refinish with a good penetrating oil whenever it starts to absorb water (water no longer beads on the surface), you can get a decent service life and attractive hardwood appearance at a budget price.