Manchurian ash for stair treads: hardness, wear resistance and finish schedule
2026-09-17 — Yachidamo team
A staircase is one of the few pieces of joinery in a house where every step is a wear test. If the treads are wrong, the customer knows in three years. If they are right, they outlast the carpet in the rest of the room. Manchurian ash (Fraxinus mandshurica) — sold internationally as TAMO ash — is one of the better answers, and the numbers explain why.
Hardness that matches the job
Janka hardness on air-dry F. mandshurica averages 1,320 lbf (5,870 N). For comparison:
| Species | Janka (lbf) | Notes |
|---|---|---|
| Red oak (Q. rubra) | 1,290 | The US benchmark for stair treads |
| American white oak (Q. alba) | 1,360 | Slightly harder than red oak |
| Manchurian ash (F. mandshurica) | 1,320 | Between the two oaks |
| European ash (F. excelsior) | 1,320 | Same hardness, different figure |
| American white ash (F. americana) | 1,320 | Nearly identical |
| Mongolian oak (Q. mongolica) | 1,400 | Densest of the group |
At that hardness stiletto dents are cosmetic, and a decade of shoe traffic scratches the finish, not the wood. Ash also has an open, forgiving grain that hides scuffs the way closed-grain maple cannot.
Thickness and cut
- Solid tread thickness: 32 mm minimum for domestic stairs, 40 mm for commercial or oversized flights. Below 32 mm the tread deflects and the finish cracks at the nose.
- Cut: solid-lamella radial (quarter-sawn) is the professional's choice. Cupping is minimal, the wear surface has straight grain, and the nose does not lift.
- Grade: A/A, colour-sorted. B/B is fine for painted risers; save the money.
- Nose profile: 20 mm radius standard, 5 mm chamfer optional. Sharp nosings on ash chip out in year two.
Finishing schedule that survives
We ship treads raw; the shop that installs them finishes on-site. Here is the schedule that gives the longest wear in our experience with US and EU stair builders:
- Sand 80 → 120 → 180 → 240 grit. Skipping 180 shows up as haze under oil.
- Water-pop with a damp cloth, let flash off, sand 240 again.
- Base coat: hard-wax oil (Osmo 3062 or Rubio Monocoat Pure), thin coat, buffed cross-grain.
- Cure 24 h at 20 °C, 50% RH minimum.
- Top coat: second thin coat of the same oil, buffed.
- Cure before use: 5 days for foot traffic, 21 days for full cure.
If your customer wants a lacquered top, use a 2K polyurethane at 100 g/m² over an oil-based sealer — nothing waterborne on stair treads. It fails at the nose within two years.
Sizes we cut
Lamellas long enough for treads up to 1400 mm are standard. Wider than 1400 mm we glue full-length lamella pairs; the joint runs the length of the tread and never crosses the wear zone. See the Manchurian ash hub for the size table and Rockwell-style hardness certificate we send with every pack.