I am in the process of rebuilding a deck out of red cedar ( I got some beautiful clear red cedar for the important parts). There will be  a step half way along. My wife, who is an Interior designer wants to highlight the step, so we will be less likely to trip over it, and wants to inlay a strip of black slate tile, 4″ wide along the length of the 2×6″ deck board at the top of the stair.

 The tile place says it won’t work, due to wood expansion etc. I think the tile is 4″ wide, and there is little expansion and contraction over the 6″ width of the board.  Any ideas or recommendations as to whether this is possible/advisable and how to best do it?

I live on Vancouver Island, so we get lots of rain, and only a little snow and below freezing temperatures.( Like Seattle).

Robin