The Importance of Undercoat

Article by Kathleen Toohey – PaintRight Southbank



It is a common misconception that many projects can be completed without an undercoat, 2 coats of low sheen will do just fine right? No! So let’s get a few basic rules out of the way to help you along on your next project.


Undercoats have been formulated to do a specific job. They basically seal a surface and prepare it for the decorative or, top coat. They prevent surfaces from soaking up too much paint, they prevent colours and stains from bleeding through and they ensure adhesion and prevent peeling.

Without undercoats, projects would take twice as long and last half as long. Its important to get it right.


Firstly, anything that has not been previously coated should be. While this is not always 100% a necessary thing to do, it is always 100% necessary to be safe rather than sorry! So whether it is new plaster walls, timber, concrete, panelling, metal or even a canvas, be sure to give the substrate a coat of appropriate undercoat.


Sometimes undercoats require tinting, depending on the colour chosen. Particularly dark or bright colours at times require a grey undercoat; this helps with coverage and prevents the need for multiple coats. It also provides a more accurate representation of the colour. Your local paint expert will be able to tell you if this is required.


Previously coated surfaces should only require an undercoat if you are wanting to apply a water based paint over an unknown or oil based paint, if there are stains present or if the surface is rough or peeling, resulting in prep such as sanding or filling. This is mainly for adhesion purposes.

Undercoat is certainly required whenever there has been fillers applied. Fillers can be quite thirsty.


Stains such as water stains, smoke stains etc. Require a particular undercoat to prevent them from bleeding through, essentially blocking the stain, very clever!


Luckily, Haymes Paint have devised a prep coat range called Ultra Series, comprised of only 5 products, that cover all undercoat needs. This range includes 2 water based undercoats, 2 oil based and 1 spirit based. These 5 products – Ultra Cover, Ultra Seal, Ultra Prime, Ultra Lock and Ultra Hold cover every possible requirement.


For those that prefer water based paint, Ultra Cover and Ultra Seal are for you. Between the 2, there is superior adhesion, low odour as well as stain sealing properties. Ultra Cover is actually the most versatile of the whole range, best of the best.


For those that prefer the traditional oil based undercoats,the Ultra Series range has enhanced them. Ultra Lock has incredible adhesion and is rapid drying. Ultra Prime is a metal primer suitable for all metal surfaces including galvanised iron and Ultra Hold is their rapid drying stain sealer. No more waiting to apply the next coat.


Now you have a fair idea of what you need to use and why, but it is still always worth explaining your project to your local paint expert, they will make sure you are using the right thing.