My stairs are constructed of 1 inch solid Red Oak treads and 3/4 inch Red Oak risers. There are some minor gaps at the rear of the treads where they meet the bottom of the risers. The wood is stained fairly dark which helps to somewhat "hide" the gaps but I would still like to fill them some way.

I am at a loss since I do not know of a "stainable" caulk and am concerned that wood filler will not be flexible and will crack over time. Any suggestions on how to solve this issue?

Thanks

Can you get to them from underneath?

Jerry,

Unfortunately no. They are enclosed on both sides.

There are colored flexible fillers usually offered by laminate people. Pergo has their own branded product in assorted colors. It come in a caulking tube. Other than that Bruce makes a decent filler in a squeeze tube available at big box stores.

Thanks Jerry. I will give that a shot.