Glued stair steps are coming loose

And the comment about lazy-minded craftsmen ... :rolleyes: No craftsman wants to fix the design errors of builders.

I was just about to say - a rigid metal connection only leads to cracks in the steps. Two screw points per side in the wood even if the connection in the wood wasn’t also made as an elongated hole. The wooden dowel only prevents the step from slipping if the glue fails again.

And the comment about the lazy craftsmen ... :rolleyes: No craftsman wants to fix the design flaws of builders.

Where are cracks supposed to come from?

If the wood cannot move freely to its full extent – i.e. swell and shrink – cracks will occur. Due to fibers being torn apart and cell collapse caused by compression damage. With a 25 cm wide step, these can be dimensional fluctuations of up to 7 mm in oak. If the step is then firmly installed during the heating period with relative humidity of 20-30%, the wood will swell correspondingly strongly in summer at 60-80% rH of the indoor air. The compression causes the cells to collapse, first leading to microcracks and eventually fiber breakage. If the wood was also not dried correctly and stored before installation (a friend of a friend had that happen once ...) then damage is unavoidable.

We are in a single-family house without large temperature fluctuations (19 to 23 degrees) and relatively constant humidity (30 to 60%). The wood can certainly "creak" sometimes, but no damage will occur.

However, it is important, and I agree with you on this, that the wood is dry when installed.

I consider the idea of sleeves to be plugged on or alternatively threaded sleeves to be screwed in as the most promising variant. The wood structure is not stressed excessively like with a screw, and the wood still has room to move. So: hole -> sleeve -> screw (in the color of the metal) from below. Form follows function!