Staircase remodel

Maybe your best bet would be to cut new stair treads

Get some quarter-round ... small enough that will do the job and close in the spaces. You could also use moulding. Or if the spaces are small enough, simply apply caulking.

Could you cut thin baseboard into pieces and glue them along the wall to cover the space and it would even add a nice decorative element to the stairway.

Those are made out of builders grade construction lumber. Obviously they were made to be covered or were covered with carpeting at one time. I agree with Paymetotellyou. Use quarter round molding to cover the gaps. Gaps are to wide for caulk.

I agree with Paymetotellyou--hide the gap with quarter-round after you stain the stairs. If you were installing a floating floor, you'd need to leave a gap so the floor could shrink and expand, and you'd hide it with baseboard and quarter-round. You could do the same with your stairs. Whoever built those stairs may have left the gap intentionally to allow the wood room to swell in high humidity.

If your budget it tight here's a lot of options wood mold on both sides of the stairs and paint those white to match the sides, unless you use decortive tiles on the risers the will take away those defective spaces, I found a photo of all these ideas For you. That's nuts that they did a shotty job and your left to fix there mistake!! I hope I was of some help to camouflage your project📌

That is a excessive gap for expansion. Shoe moulding on the rise the painted white part that is where the eye is drawn too. The treads you can leave by the look of pics they look to be cut better .

There's a great product called deckover by behr. Home depot has it. Great product..

My brother and I are actually doing this right now......Plastic Wood from the hardware store, pressed into the gaps, clean that bead with your finger tips (gloved), sand after a day, then paint or seal however you like. I will take pictures and post. It looks amazing!

do nothing rustic look is good