Example Of A Poor Stair Support

The support needs to be underneath the stringer, not next to it. The support in the picture above can weaken over time and of course could rot from the bottom where the wood is touching the concrete.

structural support for stair stringer

In the illustration above, the structural stairway support is underneath the stringer and it wouldn't be a bad idea to use a 12 inch long metal framing hardware strap to connect the stringer to the structural support.

metal framing hardware bracket post connection