undercoat emulsion on walls ?
Do I need to undercoat emulsion on walls that have been previously painted and are in good condition. Even with a big colour change, a first coat of undercoat is for the most part, a strange concept, but sadly it is a question that is gaining traction.
I was asked by a Swedish client just today about undercoat for walls. Where has the icon for head-scratching gone?
There are occasions where this undercoat idea might apply, (see at the end) but for most standard redecorating work, preparation plus 2 coats of emulsion works just fine. If you need 3 coats due to lack of opacity, there is certainly no requirement to make the first of those 3 coats a wall primer – ordinarily.
It turns out that this idea of a first coat of primer (undercoat emulsion on walls) seems to be a Farrow and Ball thing. They specify a wall primer coat before applying 2 coats of Estate emulsion – period. F&B say it is to ensure maximum coverage. Well, maybe if the Estate emulsion paint had better opacity, they wouldn’t need to throw this red herring into the works.
So, ordinarily, if the walls are in good condition, but need a makeover, keep it simple. These days, no more than two coats of a premium acrylic paint usually suffice. I don’t use it, but premium vinyl matt paint is also usually plenty good enough to achieve a solid new colour.
Changing red walls to white.. No need to undercoat emulsion on walls , but you should be prepared to cut in the edges 3 times, and apply at least 2, possibly 3 coats overall, depending on your brush, technique, surface and paint. But don’t think you need to buy in a special tin of primer for the first coat. If you are going white, a good white emulsion is fine from start to finish. Thin the first coat say 15% and subsequent coats 10%. “Matt” generally offers better coverage than “vinyl matt” or higher sheen wall paint.
Paint a chrome yellow acrylic wall paint over a different colour. In this extreme case, you might be best advised to apply an obliterating coat of white acrylic emulsion first, then 2 coats of yellow. (Yellow pigment for paint is notoriously weedy, and for some reason, blues especially are a pain to cover with straight yellow.) Using white first will save a little bit on cost of materials. But again, a special wall primer over solid previously emulsion painted walls is absolutely not required in normal circumstances.
Undercoat before painting walls with emulsion
There are circumstances where you “undercoat” before emulsioning, but it isn’t an undercoat, it is primer or sealer coat.
If the wall you are painting is flaking or patchy. In this case, you have to consider preparing, filling and sealing (aka undercoating) the surfaces prior to painting. The sealer will bind down or even out the porosity of the prepared surface. If that is the case, I can think of a long list of problem solving paints and primers to turn to first. A high opacity obliterating wall primer is not the solution.
For a really top class finish To achieve a level of finish that has to look good under halogen light inspection, you can really up your game with a first coat of Zinsser Bullseye, or other “problem solving” primer. You are not solving any surface issues, but the primer. This gives a really solid base for 2 top coats of emulsion. But this standard of finish is far removed from everyday good quality decorating requirements. ie it is one to for discerning clients who want something really special and accordingly it is a premium priced specification. .
Even with a basic spec of 2 good coats of emulsion, the better painters out there raise the bar, by thoroughly sanding ALL of the walls before the first coat. To go to another level, for a super finish, sand again with 220 grade abranet before the top coat of emulsion. Sounds like a lot of extra faff, until you have a Mirka CEROS sander, Abranet and a Wooster dust eater in your hands.
For US paint coverage, take a look at Jack Pauhl’s tests on bare drywall. No problems with 2-coat coverage with BEHR Premium Plus Flat Enamel by the look of it.
If you are in the UK there is no need to feel left out of the American party. We could get 2 coat coverage of strong colours over bare Toupret TX120 skim filler with Mythic (American brand) paints. Benjamin Moore paints boast exceptionally good coverage too.
The main thing to remember is that material costs are no more than 20% of the cost of a job if employing a professional. But cheap or inappropriate materials or daft specifications requiring to undercoat emulsion on walls can add a lot of extra labour costs, or waste your time if doing it yourself.
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