Flooring – How to fill this gap between two areas of flooring

Most installs I have done we have trimmed around the fireplace. There are several ways to do it. If your fireplace hearth sits on flat ground we try to meet even - which is almost impossible unless you did the floor and hearth all in one install.

Most of the time we trim around the fireplace first and then cut to the trim. This is very very very time consuming because you will potentially have a lot of boards meet the trim and they need to be within 1/32".

An easier way to do this, especially if the hearth material is not as even, is to add a riser then maybe an optional board (or partial board). So you would layout your wood and just get as close as you can to fireplace then nail down the riser around the fireplace. The corners take some work but this is pretty easy. This looks really good if it is brick and you can get (or notch) the riser so its back sits in a mortar line.

And a note on floating - I would probably use a riser. Because you could set the floating wood 1/4 inch from fireplace, giving it a proper gap, and then staple the riser just to the underlying floating wood. It would still be floating then.

Yes you need to keep expansion room at the walls for the flooring to move. Particularly at the walls that meet the long sides of the flooring, this is where the movement really occurs. In your picture you have the end grain of a piece meeting your transition strip. That will be no concern for movement there, although I would still get a small gap, minimally an 1/8", most certainly not tight, since the wood does move albeit slightly, in its length. That mainly depends on how much "grain runoff" is in any one piece of flooring, an 1/8" should cover it though. This gap at the wood floor/tile junction is caulked with a flexible caulk, something like, but I am not stuck on the Dap 230 in a compatible color of the grout in the tile floor. You are not done yet. Before ANY caulk is done, the joint area is carefully taped off so nothing gets on the adjacent finished surfaces. The caulk is set in place and wiped down to a clean WET joint. while it is wet have the grout on hand that was used to grout the joints in your tile floor and lightly dust the wet caulk so it dries into the caulk. This will give the caulk that varied natural look of grout, instead of the monocolor that caulk alone can't do. Peel the tape immediately after dusting and let dry, then vacuum the excess dust, the rest will remain.

You may decide to use a ready made color matched sanded caulk, that may work, but I have removed this type of caulk before and it is not as flexible as the "230" I mentioned before. No I am not an affiliate of DAP, I just know what works....