I'm laying tiles over existing tiles, an additional space to the left will be tiled over as well (photo attached), I've fixed 12mm hardboard to the wall to level off the difference. Gaps have been filled with foam. Do I need to fix scrim tape with compound over the joints between the hardboard and old tiles to avoid cracks? Gaps are approx 1cm wide (filled with foam).
Any advice is much appreciated.
Any advice is much appreciated.