A common mistake when people repaint their homes that I see very often is painting latex over oil paint without preparing the surface properly beforehand. This will result in the paint peeling off after a short while and a lot of unnecessary work to remove the latex paint from the old paint that you could have avoided if you prepared the surface correctly in the first place. It is quite rare that walls are painted with oil paint but trims and doors are often painted with oil-based paint so you should be especially careful when painting those.
As a whole, to paint latex paint over oil paint it is important that the surface is prepared properly. To prepare the surface sand it first and then apply a primer. Latex paint can now be applied directly to the prepared surface. Sanding is not required if an extreme bonding primer is used instead.
There are some smaller things that you need to keep in mind when painting Latex paint over oil-based paint to achieve a good-looking result. I will go over the steps and everything that you need to watch out for in more detail in the section below.
Why Applying Latex Directly to Oil Paint is a Bad Idea
You might be wondering why you can´t paint latex paint directly over oil-based paint without properly preparing the surface first and even though most experts make it out to be a very complicated thing to explain it actually isn´t hard to explain at all.
As a general rule, if you paint latex over oil without preparing the surface first then the latex paint will not stick properly and it will peel off after a short while. This is because latex paint is water-based and can´t adhere to oil-based paint. But oil-based paint can adhere to latex paint.
If you ever tried mixing water with oil then you know exactly what I am talking about.
Water and oil don´t mix at all. Oil will always separate itself from the water.
Pretty much the same thing happens if you try to apply water-based paint, such as latex paint, to oil-based paint.
Interestingly enough, it is possible to apply oil-based paint to latex paint without any issues.
But why is that?
Well, water-based paint dries through evaporation. Meaning the water in the paint will evaporate and the latex paint will dry and permanently adhere to the surface it was applied to.
Once this process is done there isn´t really any water left within the paint. So there is nothing left that would hinder the oil-based paint to adhere.
And while it isn´t perfect to apply oil-based paint directly to latex paint it would work.
How to Paint Latex Paint Over Oil Paint
Now that you know that applying latex paint directly to oil paint is a bad idea it´s time to look at how to do it properly.
Here is a quick list of materials and tools that you will need for this guide:
- 150-grit sandpaper
- A paintbrush or a Paint roller
- A putty knife if you have to remove old peeling paint
- An old towel or a piece of cloth
- Paint primer
- Latex paint
- Wood filler or quick filler if you have to fix holes or cracks in the surface
You can get most of it at your local hardware store. Pretty much any latex paint will be sufficient.
I personally prefer quick-drying latex paint because it lets me work faster but you don´t really need to use quick-drying latex yourself. The result will be pretty much the same.
But you should be careful when choosing the right kind of paint primer. You need an extreme-bonding paint primer.
You could use regular primer as well but I found the results to be inconsistent. Sometimes the primer would adhere perfectly and other times it would crumble after a while.
This is why I personally prefer using an extreme-bonding primer to ensure that the primer sticks properly and permanently.
My favorite primer to use is the high-bonding interior latex primer from KILZ. You can buy the primer right here on Amazon.
1. Remove Old Peeling Paint
First things first, if you already applied a coat of water-based paint on top of the oil paint then you need to remove it.
The coat of water-based paint will either not stick very long or maybe it already started peeling off. Either way, you need to remove it before you can start preparing the surface properly.
TO remove the previous coat of paint simply use your putty knife to peel it away. The paint should come off relatively easily and without the need for much force.
Remove as much of the peeling paint as possible before moving on to the next step.
2. Sand the Surface
After removing the old peeling paint it is time for sanding.
You don´t always have to sand the surface. Most modern primers, the one I recommended earlier included, will stick to oil-based paint just fine.
So you could skip this step if you want to but I would still recommend sanding before applying the primer to ensure that the primer adheres properly.
Sand the surface by using 150-grit sandpaper to rough up the surface of the oil paint. You don´t have to remove the oil paint by sanding it is more than enough to rough up the surface.
This will make it easier for the primer to properly adhere to the oil-painted surface later on.
3. Clean the Surface
This step is very important even if you skipped sanding the surface you still have to clean it properly to ensure that the primer adheres to the surface.
This step is pretty straightforward. Just use some water and an old towel or a piece of cloth to remove any dust and dirt from the surface.
4. Apply the Primer
Now it´s finally time to apply the primer. Primers are painted on the surface just like regular paint but other than regular paint they will adhere to most surfaces and they will prepare the surface for being painted.
So use either a paintbrush, a paint roller, or both to apply multiple thin coats of the primer.
Let the primer dry in between coat applications.
It usually takes around 2 or 3 coats until the primer covers the underlying coat of paint completely.
You can use fine-grit sandpaper to further smooth the surface of the primer if you are not satisfied with the result or if you see some dried drops or something similar.
5. Apply the Latex Paint
And the last step is painting the surface.
After doing all of that the surface is finally ready to be painted.
So apply the latex paint in multiple thin coats to the surface. You can use a paint roller or a paintbrush to apply your paint.
Let the paint dry in between coats. It really depends on your paint but most paints will cover fully after 2 to 4 coats.
And you are finally done! You have successfully painted latex paint over oil paint!
How to Paint Over Oil Based Paint Without Sanding
The most time-intensive step in this whole procedure is, without a doubt, sanding the surface before you can apply the primer. So, naturally, people often ask me if it is possible to paint over oil-based paint without sanding the surface first.
As a whole, to paint over oil-based paint without sanding a high-bonding primer has to be used and the surface, that will be painted, needs to be intact and clean. Simply apply the high-bonding primer directly to the surface and let it dry. Then apply the paint to the freshly prepared surface.
It is important to note that you can only use this method if the surface that you want to paint is intact and no paint is peeling off of it.
Also, while it is possible to simply apply a high-bonding primer directly to oil paint it is still recommended to sand the surface first to ensure that the primer adheres properly.
In rare instances, the high-bond primer can still have a hard time bonding to oil paint.