Everyone is budget conscious and when it comes to deciding if you should spruce up your home it is no different. For most people painting interior rooms is high on their list of projects but for first time painters and those who have not attempted it for a while the decision to simply buy paint or buy primer and paint may make you think twice about if you can afford to do it or not.
There is no real simple answer to this question. If you were to ask a professional painter or paint sales person they would almost always suggest that a base coat of primer should always be applied. This may be for the protection of the contract by a professional or to generate more income for a paint store but in reality it is not always necessary to use primer when painting over surfaces that have already been painted.
That is one of the key first deciders… has the wall or item you are painting been painted before.
If you are painting new drywall you should always apply a coating of primer. Primer on new drywall will reduce the absorption of the higher cost top coat paint but it also seals out the bare compound areas.
At the very minimum whenever you have a repair or new drywall with fresh drywall compound covering nails, screws or taped areas you always want to cover it with primer first or you will never get a uniform coating with your top coat paint.
Should Pre-painted Walls be Painted with Primer before the Top Coat?
This will depend on the condition of the surface and the former and final color of the wall.
First the condition of the wall must be evaluated. If you have a wall with a lot of chips or scratches it might be worth using a spackle compound and then primer. This can happen if you have dogs or children or just an area that gets a lot of use.
In addition to condition is the age and location of the older paint.
If you are painting a kitchen that has not seen a remodel for a long period of time it would be worth using primer to lock out any grease that you can not remove by washing. Yes most walls in your home will need to be washed before they are painted and a mild soap will work well to remove dust and surface grease. If you are working in the kitchen some grease may embed its self into the drywall or paint making it difficult to remove so a primer should help.
What about color changes? Should you always use a Primer?
Normally you can go darker or stay within the same tone of color and not use a primer.
For instance if you had white walls you could paint any color without a primer if the wall is in good condition.
If you have a light color you could apply any darker color if the change is at least 25% darker.
If you are changing color from a medium yellow to a medium blue there is a possibility that you could end up with a greenish tone but that is not so common as painting a white or light color over a Red or Brown.
The reason you need a primer when changing colors is because the new paint you are using does not have enough holdout. Holdout can be thought of as the thickness of the paint and it would be similar to holding a glass of Tea against your wall or a glass of Milk … the tea will show the color underneath but the milk won’t and that is because it has solids in it that block or holdout the color under it.
Some manufacturers rate their paint for holdout but most do not make official technical information available. The difference in a good paint and a cheap paint could be holdout but this is not always true.
So is Primer always necessary when painting?
No it is not always necessary to use a primer under your top coat.
However if you have new walls or repair areas they must always have primer.
If you have a darker to lighter color change it can be worth your money to buy a primer so you will not need to second coat your top coat to get the right color.