last updated 2 July 2024

You cannot apply latex paint over an oil base because it will not adhere properly and will peel or scratch off easily. In general, you should always put an oil-based paint over an oil base, and water-based paint over a water base. Although you can paint oil over latex, over time it will crack. The only exception to these rules is alkyd primer. Most alkyd primers are formulated to go under both oil and water bases.
In Latex Paints Over Oil-Based at Paint Quality Institute they say:
The rule of thumb is that, given proper surface preparation, for exterior use you can apply quality latex paints over oil-based, but not the reverse. However, if you have many layers of oil based paint, stick to using oil on oil.
Another article stated:
Up until recent years, painting latex over oil was taboo since it had no adhesion properties designed to make it stick to oil surfaces, which meant that you could literally take it off using a fingernail or even just attempting to wash the wall.

If you can paint latex over oil based primer, why can't you paint latex over oil based paint?
The reason why latex can be painted over oil primers is because oil primers are formulated differently than oil finish products. Oil primers actually have a lot of flexibility, allowing them to move, much like latex. Oil paints are much too hard when they dry, not allowing for much flexibility at all.

We would not recommend using a latex primer to be coated with an oil finish in most exterior cases due to the difference in flexibility, but an oil/alkyd primer under latex finish paint is a good method.

For interior surfaces once they are properly prepared and primed it is not an issue to apply oil over latex or latex over oil. Modern primers will accept either over either. The relatively new High Performance interior acrylic paints claim to be the self-priming super stars of interior trim paint.

Painting oil-based paint over latex paint is generally considered a mistake because the two paints have different characteristics that can cause the surface to crack and split. However, there is one exception: waterborne alkyd paints, which are low in volatile organic compounds (VOCs) and can be applied safely over latex paint. Waterborne alkyd paints are often used on wooden cabinetry and can provide a durable, clean finish.

Painting with an oil based paint over latex is OK but doing the reverse will cause you grief for many years to come since any further coats of paints applied will stick to the latex only.

And remember, never apply oil paints over latex unless you are using a waterborne alkyd which will safely coat the more flexible layer beneath.

One of the most common mistakes in painting is applying oil over latex paints. Although, despite this simple rule, it can raise other concerning factors: can you use a waterborne alkyd over latex paint and vice versa? And if so, does it require a primer? Today we will discuss these concerns as well as give a quick tutorial on how the process should be executed. If you have any questions about this blog or any other paint related inquiries, please contact your local Houston Interior Painting?experts, Pro Painters, for additional information.

Sometimes it can be difficult to determine if it?s safe to apply oil paint over latex paint, but we assure you, overtime it will ruin your surface. Due to the flexible qualities of latex paint and the brittle characteristics of aged oil paint, it can eventually split and crack the painted surface. Another concern is whether or not it?s safe to apply waterborne alkyds over latex. Waterborne alkyds are a low-VOC paint that provide a clean durable finish and are mainly used for wooden cabinetry. They are available in odor-free options and can safely be applied over latex paints. Although, perhaps one of the best features about alkyds aside from providing protection to your surface, is that you rarely have to apply a primer on top.

If you plan on using waterborne alkyd paint over latex paint we first suggest that you thoroughly clean the surface you will be working with. This is a key factor. The surface must be free of all dust and grime as well as any wax, oil, grease, or mildew. In addition, try your best not to have any soap or water soluble materials left over from the cleaning. You want it to be bone dry. If there are any peeling flakes or blemishes in the surface, you?re going to need to properly sand off these areas so everything is clean, crisp, and uniform. Next, begin applying your alkyd paint. It is best to use a nylon/polyester brush or roller. Also, you should consider setting up additional ventilation in your work area to ensure that the paint dries rapidly.