Wood That Sinks in Water: Which Species and Why

Explainer · 3 min read · Updated October 2026

Which wood sinks?

Wood sinks when it is denser than water, which means a specific gravity above 1.00. Very few species do, and the ones that do come in small pieces. They suit bearings, mallets and turned objects, not doors.

Chart of specific gravity at 12 percent moisture: black ironwood 1.35, lignum vitae 1.26, gaboon ebony 0.96, with water at 1.00 as the sink or float line — Above the 1.00 line, the wood sinks. Source: The Wood Database.

This page explains what makes a wood sink, which species do it, and what to expect if you work with one.

Table of Contents

What makes wood sink?

It comes down to density. Specific gravity is the ratio of a wood’s density to that of water, with water at 1.00. Any wood above that number is denser than water.

The Wood Database gives two values for each species: a basic figure measured on oven-dry weight and green volume, and one at 12 percent moisture (The Wood Database).

Most species sit well below 1.00 and float. A few tropical hardwoods and shrubs pass it, and moisture matters: a dried board of one species can be lighter than a green one.

Aerial view of rafts of stacked timber floating on dark blue water — Most timber floats, which is why logs have long been moved by water.

The woods that sink

Lignum vitae (Guaiacum officinale and G. sanctum) has a basic specific gravity of 1.05 and 1.26 at 12 percent moisture. It weighs about 78.5 pounds per cubic foot and has a Janka hardness of 4,390 lbf.

It is used for tool handles, mallet heads, bearings, bushings and pulley wheels, and its natural oils make it self-lubricating.

Black ironwood (Krugiodendron ferreum) is 1.07 basic and 1.35 at 12 percent moisture, at about 84 pounds per cubic foot and 3,660 lbf. It grows in southern Florida and is among the heaviest woods on earth. The tree is barely larger than a shrub, so it is not sold commercially and small pieces are used for turned objects.

Ironwood wattle (Acacia excelsa) is a shrub or small tree whose wood is so dense it sinks, at about 71.8 pounds per cubic foot and 4,050 lbf. Gaboon ebony is hard at 3,080 lbf, but at 0.96 specific gravity when dry it is just under water’s density. It is used for piano keys, instrument parts and small carvings.

Working very dense wood

Dense wood is hard on tools. Lignum vitae tends to skip over jointer cutters, so take very light passes, and it dulls cutters.

Its oil makes strong, reliable glue joints difficult, and finishing can be a problem, though it turns well on a lathe. It has been reported to cause skin irritation, so use dust protection.

Working with very dense wood: take light passes, expect dull cutters, glue oily wood with care, turn it on a lathe and wear a dust mask — The shop notes for lignum vitae and other very dense woods. Source: The Wood Database.

Sustainability and cost

Lignum vitae is listed in CITES Appendix II and as endangered on the IUCN Red List, because exploitation of the wood and its resin continued for hundreds of years. Trade is restricted, and prices for genuine lignum vitae are very high.

Gaboon ebony is also on the IUCN Red List as endangered, after a population decline of more than 50 percent over three generations. Check the source and the paperwork before you buy either one.

Our take · James Davis

Treat these woods as specialty stock for small, high-wear parts, and buy a little from a seller who can document the source. For anything the size of a door, choose a species that grows in boards and takes finish well.

What this means for doors

A door needs wide, stable boards, and the sinking woods grow as small trees or shrubs. Door makers use species such as mahogany, white oak and fir, or they use a fiberglass or steel skin over a core. See our guides to front door materials, solid core wood doors and fiberglass doors for exteriors.