Prepcoat? Undercoat? Sealer? Primer? What’s the difference?

It can be pretty confusing when these terms start getting thrown around when talking about DIY projects. There actually is a difference between these products, and often then terms are actually used incorrectly. Not to worry though – we’ve broken it down for you!


A “prepcoat” is actually the term used to describe all “preparation coats”; so primers, sealers and undercoats are all technically prepcoats!

A prepcoat is any coat of paint applied to your substrate to prepare for the application of the topcoat. When painting a new surface, the prepcoat is actually the most important step of a panting project!


A primer is the first coat of paint applied to the substrate. A primer has many purposes, including:

- Blocking out stains and tannins
- Stops rust occurring on a metal surface
- Smooths out imperfections on a rough surface
- Creates a barrier to stop moisture travelling from the substrate to the topcoat
- Some primers contain properties that assist to prevent mould and fungus from developing


A sealer is a special type of primer designed to be used with, or in place of, a primer. A sealer prevents the topcoat from soaking into the substrate, and to a degree, can create a water-resistant layer between the substrate and topcoat.


An undercoat is used after a primer. It is used to fill any minor imperfections to create a smooth, even-coloured surface ready for the application of the topcoat. An undercoat also assists to lighten a surface when changing from a dark to a pale colour.

Typically, today you can buy a three-in-one prepcoat product that saves time, money and confusion! Berger Premium Triple Prep or Dulux 1 Step™ Acrylic Primer Sealer & Undercoat are great options for your prepcoats.

If there is still a bit of confusion about prepcoats, or you’re unsure what is needed for your next project, head into your local Inspirations Paint store to chat to our friendly and knowledgeable staff!