ChaseTiling

Its internal render that you have there.

2 options :

1. Brush off then let to dry; apply bonding coat to level the surface. Leave to dry then prime using 3:1 acrylic primer before tiling as normal, otherwise the old and new plaster will suck the moisture right out of the adhesive to quick and your tiles will fall off.

2. Dot and Dab 9.5mm board onto the existing DRY + BRUSHED render and tile as normal.

Option 2 is the quickest and cheapest.

Good luck!!

Ant - Chase Tiling Academy

Tiling NVQ and Tiling Courses
TF Resident NVQ Advisor: Any questions or advice you need on getting an NVQ, then please ask me. Either PM me or post your questions in the NVQ part of the forum, where I shall be sat.