Renders can be a variety of surface finishes, but usually they are not as smooth as a plaster finish
Using Thin Coat Render as a Finish for Internal Surfaces
If you have a rough surface, a repaired render or a rendered finish you are not satisfied with you can consider to apply a thin coat render with a smaller aggregate size of no more than 0.6 to 1mm on top of the existing render.
Thin coat render is a pre-blended cementitious render with the addition of additives to increase adhesion and improved workability. This will be faster, more economical and a better looking surface than any other method.
This is what you need to consider:
Ensure you finished all repairs before applying on coat of thin coat render. Apply to a thickness of around 2 mm, allow some time to cure and use a sponge float to finish. If you like a surface that is smooth to the touch, but still slightly textured use a stainless stell trowel and at the right time push all grains that are proud of the surface back level to the surface.
Allow to cure and protect the surface from all sorts of contamination, such as grease, fat, oil, wax, but also acrylic gap fillers or paint when painting door surrounds or architraves.
Brush off dust and all loose particles prior to applying two coats of limewash paint. There is no need for any primers or Prep Coat.
1 liter of limewash will be enough to cover approximately 7 - 10 m2. We recommend two coats of limewash paint for such a surface.