ᐅ Concrete staircase with varying step heights

Hello everyone,

We had a cast-in-place concrete staircase installed in our newly built single-family house. Unfortunately, the builder neglected to measure the staircase right after the formwork was removed.

Yesterday, a staircase specialist visited the site to take measurements and noticed that the step heights vary by up to about 2.5cm (1 inch). This definitely needs to be corrected. He recommended leveling the height differences using OSB boards. Later, a wooden tread will be glued on as the step covering.

Here are my questions for you:
The staircase was poured last August. Does it still have residual moisture? Or should the concrete staircase be treated with a sealing or waterproofing coat? I am concerned that the wooden treads might swell later on.

Also, I am surprised that the stair builder wants to use OSB boards to level the height differences. This would create an additional layer that needs to be glued on. Wouldn’t it be more sensible to even out the step heights with concrete?

Thank you very much in advance.

Best of luck,
julianpe

When pouring concrete over the "old" concrete, a proper bond does not form.
In this case, bonding and/or screwing is better.
The residual moisture should be measured easily. However, it should be fine after some time.

Are there alternatives to OSB boards for leveling?

Of course, there are alternatives. Whether they are practical is another question.
In theory, this is also possible with the final floor covering if it is available in a sufficient thickness...
What do you find unsuitable about OSB as a subfloor?

We currently have a concrete staircase with glued wooden treads in our rental house. However, since almost all of them are loose, the previous tenant connected and screwed the treads and risers together with metal brackets.
When walking on the stairs, you can hear that not all the wooden steps are still secure.
Without further experience, as an amateur, I would suggest: screw the “leveling layer” onto the concrete and glue the wooden steps. Presumably, glued wood-to-wood joints hold better than wood-to-concrete.

I agree! It is definitely dry in any case.