I know that it depends on the wood itself, but are there any guidelines for how thick each stairstep should be?

Assuming that it will be held by its sides (with no middle support) and will be around 100 cm (39 inches) wide.

I think the same rationale here could be used for shelves, but I also haven't found anything on that either.

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    The stringers can't be moved because the stair style demands the open space between the steps. I thought about 8 cm (about 3in) but it might be very large and make me lose some of the "openness". Another thought is reinforce each step with metal bars inside (joining two planks with the reinforcement to make each step). Aug 12, 2013 at 19:02
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    in terms of reinforcing with metal, the undersides of say, 5/4 oak (full 1" thick), could be fitted with 4 or 5 lengths of upside down 1/16" or 1/8" by 3/4" iron T-shaped stock. By 'fitted' I mean cutting a kerf for the upright, and a dado for the flat. The T-bar would run the full length, or nearly so, of the tread and be directly supported by the stringers.
    – mike
    Aug 12, 2013 at 19:12
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    Instead of reinforcements in the bottom (which would detract from the open look of the stairs), I thought about reinforcing the middle. Maybe a 3 cm top plank with 2 or 3 dados cut lenghtwise for receiving square tubing, then another thinner plank (1 cm maybe) is glued/screwed on the bottom covering the reinforcement. Finally the step would be screwed by the bottom to the metal stringers (like this one metal-craft.net/graphics/sta0204.jpg). Is square tubing better or worse than T-bars? Aug 12, 2013 at 23:24
  • With the T-bar idea that I outlined, the lengths of T-bar would be fully embedded in the 5/4 oak tread.
    – mike
    Aug 13, 2013 at 3:13

1 Answer 1


At that length and with a decent thickness (>=1 1/2") you'd probably be fine just using a solid wood plank as long as the species is appropriate. Here's a chart of the modulus of elasticity for some common woods


To be honest, when designing something like a staircase you should really consider having it engineered by an architect or structural engineer just for peace of mind.

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