Masonry paint on internal walls

[Bek81]

Im about to start a small project making an office space in a small room/large cupboard under the stairs. The previous owner seemed to have painted the plastered walls with masonary paint. I want a smooth finish on the walls and am wondering how i should go about removing the paint? will it lining paper over?, whats best? Anyone else had this bizarre problem?

 

[AkiN]

Is the existing masonry paint textured? If so and it's in good condition then it'll be difficult to remove. If flat and in good condition either repaint directly on top or line and then paint.

 

[Bek81]

Yes its textured, feels like sandpaper. The wall is flat and apart from bits that have pulled off around the raw plugs where shelves were removed, is in good condition, just not my taste. Will the texture show through a thick lining paper?