Shellac on wood floors?

I recently had wood floors installed. Great job. But the installers used shellac on the stairs. I’ve had friends tell me this was a bad idea, and that I should put a coat of poly over it.

Here are the questions:

Is shellac ok for floors?

If not, is there anything I can recoat it with short of sanding the stairs completely.
Thanks for any help. Know this is a narrow question, but the net was of little use.

Shellac is what used to be used on floors in the days before poly.
My house’s 80 yr old floors are shellaced. It’s still holding up well in most places.

You may want to check exactly what brand of shellac they used; I don’t think there are any major differences but the ready-mixed type that I use for woodworking notes that it shouldn’t be used as a sealer under polyurethane.

FWIW I like shellac - it’s very easy to apply and clean up after. I think the only thing it’s vulnerable to is alcohol which dissolves it. I use it for shop cabinets and fixtures and stuff like that.

I wouldn’t use shellac on floors as a finish coat. It’s easy to scratch and susceptible to some solvents, especially alcohol. It is waterproof, but not usually attained on wood without multicoat.
It is unsurpassed as a sealer and transition to almost every finish known EXCEPTING most urethanes.
I’m referring to shellac made with the crushed shells of the lac bug. “Shellac” is an oft used misnomer for other finishes. Make verification before proceeding.

You might want to double check this carefully. Doesn’t seem right. Shellac hasn’t been generally used for floors or stairs for a long, long, long time.

Watched the guy brush it on. Didn’t know any different at the time.

The voters here seem split, but thanks all for the help.

You might want to watch out for ammonia too.

It might interest some to know that shellac is made from* insect secretions*:

I was wondering about that - you use warm water and sudsy ammonia to clean the brushes but I wasn’t sure what it would do to a dried finish.

Anyhow while I like to use shellac as a finish (fast and simple to apply) I’m aware of the limitations. I wouldn’t use it on a floor since it’s subject to spills and harsh cleansers.