Slippery Elm
Ulmus rubra · hardwood · Eastern North America · moderate movement
- Janka hardness 860 lbfred oak ≈ 1,290 lbf
- Density ≈ 37 lb/ft³specific gravity 0.53 at 12% MC
- Shrinkage — tangential 8.9%flatsawn width, green → ovendry
- Shrinkage — radial 4.9%quartersawn width
- T/R ratio 1.8 : 1higher = more cupping in flatsawn stock
Shop notes Similar to American elm in the shop — bends well, splits poorly (a virtue), and moves noticeably across flatsawn faces.
Seasonal movement at a glance
Width change for slippery elm across a typical indoor year — 6% moisture content in the heated winter to 12% in a humid summer:
| Board width | Flatsawn | Quartersawn |
|---|---|---|
| 6″ | 1/8″ (0.114″) | 1/16″ (0.063″) |
| 12″ | 7/32″ (0.229″) | 1/8″ (0.126″) |
| 24″ | 15/32″ (0.458″) | 1/4″ (0.252″) |
| 36″ | 11/16″ (0.687″) | 3/8″ (0.378″) |
Run your own numbers
Different width, different climate swing — the calculator below is preset to slippery elm:
Typical swings:
Slippery Elm questions
How much does slippery elm move with the seasons?
A 12″-wide flatsawn slippery elm board moves about 7/32″ across a typical indoor swing from 6% to 12% moisture content; quartersawn, about 1/8″. Its tangential shrinkage is 8.9% and radial 4.9% (green to ovendry) — a moderate-movement wood.
How hard is slippery elm?
Slippery Elm rates about 860 lbf on the Janka scale — softer than red oak but sturdy (red oak is roughly 1,290 lbf). Density runs about 37 lb/ft³ at indoor moisture levels.
Is slippery elm good for wide panels and tabletops?
Yes, with normal precautions: its 1.8:1 tangential-to-radial ratio is moderate. Still fasten solid tops so they can move across their width.
Similar species
Black Ash · Bigleaf Maple · Sweetgum · Hackberry · Water Tupelo · American Elm
Shrinkage, specific gravity, and hardness from the Wood Handbook, FPL-GTR-282 (2021 edition), USDA Forest Products Laboratory (public domain). Values are species averages — individual boards vary with growth conditions and how they were dried.