Is a Primer Necessary Before Exterior Paint?

Yes, it is necessary. Primer evens out the absorbency of the surface, binds chalking and makes the paint adhere to the wall. On an unprimed facade the paint is absorbed unevenly, the colour varies and the paint fails sooner.

The three jobs of a primer

• Evens out absorbency: the render does not suck the water out of the paint, so the colour looks the same everywhere.
• Binds the surface: it consolidates chalky render and old paint.
• Improves adhesion: it forms a bridge between paint and wall.

Which primer for which surface?

• New render and concrete: an alkali-resistant exterior primer.
• Sound old paint: an opaque primer that suits the paint system.
• Chalky, weak surface: a clear, deep-penetrating primer.
• Surface with hairline cracks: a filling primer that fills the cracks.
• Surface to receive silicate paint: a silicate-based primer.

Can thinned paint be used instead of primer?

Only if the manufacturer explicitly recommends it. Diluted paint does not do the job of a primer; it does not bind a chalky surface or even out absorbency.

Must primer and paint be the same brand?

It is enough that they belong to the same system. Manufacturers test primer and top coat together, and the guarantee usually depends on that system.

How long do you wait after priming?

For the time stated in the product data sheet; in cold, damp weather it is longer. Erdağ Yapı names the primer and paint in its quote; details are on our exterior facade paint page.