Hello everyone: I am about to expand my solid hardwood floor and I like the look of my current wood to tile transition: it's flushed wood to tile butted with no expansion gap in between. It seems like they just grouted the seem.

Should there be an expansion gap in between perhaps with a transition in between? Obviously mine held for more than 14 years so I might no need it but. Just wondering.

Thx

Hardwood flooring will expand and contract with changes in its moisture content. Moisture content is affected by the relative humidity of air where the flooring is installed. Also, a burst water pipe or other water leak could affect the flooring. Expansion and contraction direction and stability is different for different wood species, floor board width, and the way the floor board was cut from the log (Flat/Plain Sawn, Quarter Sawn, Rift Sawn). The moisture content of the flooring when it was initially installed are a factor in how much contraction and expansion will occur in response to relative humidity changes. An expansion gap could save a house from extensive damage i.e. broken pipes or damaged/moved walls in the event of a flood.
Your installation looks nice and has held up as the relative humidity has been controlled and not varied enough to cause a problem and no catastrophes have occurred.
A problem in the center area of a floor would cause the boards to expand against each other and buckle upwards. A problem at the perimeter rows will expand into the expansion gap, if there is one, otherwise will push against any vertical 'obstructions'.
If it's been ok all this time then leave it as is.