On Monday, 4 February 2019 13:01:35 UTC, www.GymRatZ.co.uk wrote:
On 04/02/2019 12:10, Jim K.. wrote:

Apparently something of a no no, but has anyone tiled onto MDF
successfully?

It's a window reveal in a kitchen. Old tiles detached, hardly any
old adhesive stuck to the MDF underneath.

Wondering what to use to stick them back?

Not MDF but I've had a problem with the floor tiles I laid onto green
chipboard.

Originally we were simply going to extend the wood flooring into the new
extension then, like they do, the good lady changed her mind and wanted
tiles.
To cut a long story short I'm still waiting for any remaining tiles to
loosen. The ones that parted company so far have all been over the end
joins of the chip board.

Needless to say my favourite anything-to-anything building adhesive has
been used to re-attach the tiles to the floor.
Gun Grade expanding foam!

Where possible I left securely fixed tile adhesive on parts of the tile
to give correct height alignment with adjacent tiles. Sanded top surface
of chipboard to remove any waxes etc., mist chipboard and tile underside
with water, apply foam to back of tile and position. Add a few weighty
weights that overlap to surrounding tiles to ensure the foam doesn't
have chance to expand and lift tile and leave long enough for foam to
fully cure.

Still haven't grouted the tiled floor yet but the tiles that have been
re-fixed with foam are very solid and the one I did try and re-lift
wasn't coming up without breaking so I left it alone.

You might want to hold the tiles in position with a bit of flat timber
braced from opposite reveal or allow foam to fizz out a little before
applying tile to MDF as this seems to break the external skin of the
curing foam leaving a very tacky residue that seems to have very little
ability to expand any further and can be held in position by hand for 5
minutes or so until foam has stabilised

Damping both surfaces before applying foam ensures a quick and full cure
of foam.

Sounds like a bodge but I can't immagine anything else working as well
or being as easy/quick/economical to apply.
Gun and gun foam are invaluable. The foam doesn't go off in the gun
either unlike stuff like Gorilla Glue that you use once and what's left
inevitably cures in the pot.

Pete

Expanding foam is about the worse stuff one could use for floor tiles. If there's one thing such tiles must have it's rock solid support all over - far more solid than any foam could possibly give.

Tiles on MDF, chipboard etc are also bodge jobs. You can do it but don't expect it to last well.

Next someone will be suggesting silicone as floor tile adhesive! I've got the results of that, thanks to some previous bodger.


NT