Species data
Northern Catalpa
Catalpa speciosa - a hardwood from eastern United States, naturalized across North America. Also sold as catalpa, catawba.
Properties at a glance
| Janka hardness | 550 lbf |
| Stiffness (MOE) | 1,210,000 psi |
| Specific gravity | 0.46 |
| Density | 28.7 lb/ft3 (460 kg/m3) |
| Weight per board foot | 2.39 lb |
| Shrinkage, green to oven-dry | 4.9% tangential / 2.5% radial |
| Indicative price | $6.00 per board foot (estimated) |
Values are at about 12% moisture content. Density is specific gravity times 62.4; a board foot is one twelfth of a cubic foot, so weight per board foot is that density divided by twelve. Anything marked estimated is our own figure, not a measured one.
How Northern Catalpa compares
Measured against the 113 solid woods in this database: it is harder than 21% of them, heavier than 20%, and stiffer than 14%.
What that means in the shop
A 4/4 board 8 inches wide and 8 feet long is 5.33 board feet, so in Northern Catalpa it weighs about 12.8 lb. A stack of ten is 128 lb - worth knowing before you load a rack or a car.
Against red oak, the trade's usual yardstick at 1,220 lbf, Northern Catalpa is about 45% as hard and 66% as heavy.
Its shrinkage is 4.9% tangential against 2.5% radial, a ratio of 2.0 to 1. The wider that ratio, the more unevenly a flatsawn board moves across its width as humidity changes, and the more it wants to cup; anything near or above 2 to 1 is worth quartersawing or restraining for panels and wide tops. This one moves comparatively evenly.
Woods of similar hardness
Closest to Northern Catalpa on hardness in this database: Red Pine (560 lbf), Yellow Poplar (540 lbf), Jack Pine (570 lbf), Alaska Yellow Cedar (580 lbf). Similar hardness does not mean similar behaviour - check density and movement before substituting one for another.
Working with it
Workability. Mostly easy; soft latewood needs gentle sanding; turns, glues and finishes well once pores are filled
Durability. Durable, with solid performance where wood meets the ground
Typical uses. fence posts, cabinetry, carving, utility lumber.
Related calculators
Sources
MOE, SG (12% MC), Janka and shrinkage from The Wood Database catalpa page (cites USDA FPL Wood Handbook); the page covers Catalpa spp. including C. speciosa (Northern Catalpa). Uses, region, durability and workability summarized from The Wood Database. Catalpa is not listed in the FPL/Hoadley dimensional change coefficient table (Popular Woodworking reproduction), so CT/CR are omitted. Price indicative.
These calculators are for planning and estimation. Engineering results (shelf sag, wood movement) use published average material properties; real boards vary by grade, grain, moisture and defects. Verify load-bearing designs with a professional.