Problems Cleaning Open Stairway
Here's something you should give some serious thought to, while
designing or building an open stairway like the one in the picture above
and that of course would be the amount of debris that could get trapped
I don't think something like this will be a big problem, because it looks like you could slide a broom in between the steps and remove most of the debris. However, it could be a problem on larger stairways and should be a design consideration.
Now for the good news, most stairways today won't allow any sections of the stairway to be wider than 4 inches and this would include the areas in between the steps. Building designers and architects seem to be using risers to block these areas a little more often today than they have in the past.
I think this is a problem you're going to run into with older buildings and it wouldn't be a bad idea to make the necessary changes, to update them to current building codes.
Here's an open stairway that would be easy to clean under, because the sides aren't blocked.