We are removing an alcove by adding a new wall and a new doorway. However, the new wall will attach to a partly tiled wall, so will the tiles need to be removed before the area is cement rendered?

Yes, render will not adhere to tiles.

51 minutes ago, 2baht said:

Yes, render will not adhere to tiles.

Thanks. I will make sure the workers remove them before they start adding the blocks and render.

Yes remove all tiles,not a nice job and put glasses on.