Painting exterior windowsills will not only add to the aesthetics of a building, but it will also go some way to protecting them from the elements. In this blog, I’m going to talk through the important points of painting masonry windowsills and the best products you can use.
It isn’t as easy as you might think, simply because windowsills often contain moisture that can cause paint to fail over time.
How to Prepare Outside Windowsills for Painting?
I’m sure you’ve heard the old saying, “prep is 90% of the work when decorating”. Well, I don’t agree with that, but it is important. If you don’t get your prep right, then your freshly painted windowsill will not look good for very long.
Previously painted windowsills should be abraded with aluminium oxide and any loose paint should be scraped off. Bare masonry does not need to be primed unless it is grainy or chalky, or the existing paint is peeling in patches.
Assess your windowsills. If you think you do need a primer, then go with Zinsser Peel Stop. This is more of a stabilising solution, which is designed to penetrate deep into your windowsill, stabilise any unsound masonry. It will also stick down the edges of any previous paint where it has peeled and prevent it from peeling further.
It doesn’t matter how good your paint system is, it won’t last if the paint system underneath it starts to fail. So, if in doubt, prime or spot prime with Zinsser Peel Stop.
Imperfections, be it surface, or deep repairs will need to be filled. I have tried many masonry fillers over the years, but the best I have found is Toupret Rock Solid Filler (also know as Murex). You can use this filler to any depth of repair on your windowsill, but it is also good for skimming over surface indentations.
The one downside of using this filler on exterior windowsills is that it is hard to sand down, so don’t over-fill if you can help it. However, you shouldn’t need to. If you mix it to the right consistency, it is easy enough to work with. Once cured, it will last for many years.
Painting Exterior Windowsills
I can give you a few tips on painting your windowsills. Follow the advice here and use the correct materials, and your paintwork will last for years.
Remove the dust before you paint
This is an obvious one, but after you’ve sanded, you will notice a fine layer of dust on your windowsill. You need to remove this, otherwise it may hinder adhesion.
Use a good quality paint
Ensure you use a good quality trade masonry paint (I’ll get into my recommendations later). This is important for longevity.
Dilute your paint
Dilute your paint slightly for the first coat. This will help with ease of use and adhesion. If diluted, the paint will absorb slightly into any filler or bare masonry on your windowsill, which seals the material.
Paint right up to the edges
Paint right up to the edges of your windowsill and work the paint into every little gap. This will not only look better, but it will also help seal the windowsill and protect it from moisture, meaning your paint finish will last longer.
Paint the underneath
Speaking of sealing the moisture out, make sure you paint the underneath of every windowsill, even if you can’t see that edge. Miss this, and when it rains the water will run down the front of the windowsill, track underneath it, then get absorbed into the stone. Water in your windowsill will cause the paint to fail, so don’t skip the parts you can’t see.
Apply two generous coats of paint
I’m a firm believer that the more paint you apply to an exterior surface (within reason), the longer it will last. You’re asking the paint to stand up to changing temperatures, UV radiation, and moisture, and a thick paint film seems to fair better.
Painting a Windowsill
A quick tip for painti ng a windowsill
The Best Paint for an Exterior Windowsill
There are a couple of things to consider when choosing the best paint for exterior windowsills. If the substrate contains any moisture (which isn’t ideal for the reasons I have already mentioned), then the best option is an oil-based pliolite masonry paint. However, water-based is fine 90% of the time.
I’ll give you 3 recommendations, all breathable so will cope with a certain amount of moisture. I’ll give you a premium (and expensive) option, a good quality, but reasonably priced option, and an oil-based option. Just choose the paint that best suits your needs.
Emperor Paint Masonry Paint
This is the premium option, and easily the best paint I can think of to coat exterior windowsills. It is silicone-based, which makes it very breathable. It also has hydrophobic technology, which basically means it repels water. Using a paint like this offers great protection for your windowsills.
Emperor Paint also goes some way to retaining heat, which may not make a huge difference on exterior windowsills, but it’s fantastic on rendered walls. The lifespan of this paint is great too, simply because they use the best resins available.
Armstead Trade Masonry Paint
This is the “good trade paint at a reasonable price” option. I love Armstead masonry Paint, especially on exterior windowsills. The opacity, ease of use, and overall finish are brilliant. You can buy this paint at any Dulux Decorating Centre, but it’s normally cheaper to buy it online (it’s easier to get the colour you want too).
One of the things I like the most about this paint is that it is so easy to achieve a good finish on exterior windowsills. Avoiding brush marks and keeping a wet edge is made simple, so even a novice painter will achieve good results.
Zinsser AllWeather Masonry Paint
This is the pliolite (oil-based) option, so you might use it in challenging weather conditions, or when you need to stop stains from coming through the masonry.
I used this paint recently to paint a load of exterior windowsills on a house in my local area and loved it. I found it a lot easier to work with than most other pliolite-based paints, which helps when striking sharp lines. The drying time on this paint is quite quick too, so you can get multiple coats on your windowsills in a day.
Maintaining Exterior Windowsills
I thought I’d include a little section on the maintenance moving forward. Remember that painting exterior windowsills isn’t just about aesthetics; you’re also protecting your masonry from the elements. Therefore, regular maintenance will save you money in the long run.
I say regular, but if you’ve done a proper job of the painting, then it may be several years before you need to tend to your windowsills again (other than a quick wipe over if they get dirty). However, casting your eye over them and touching up any chips, or replacing any damaged sealant will mean you’ll have a longer period until you need to repaint them properly.
FAQs
Can you paint exterior windowsills with masonry paint?
Yes, a good quality masonry paint is the ideal coating for exterior windowsills. It provides the perfect protection from the elements, without trapping moisture in the substrate.
Do I need to sand exterior windowsills before painting?
You should always abrade the windowsill before you paint. This isn’t just for a smoother finish; it also aids adhesion so your paintwork lasts longer,
How often should I repaint my exterior windowsills?
This depends on a few things, including the condition of the substrate, the quality of the paint you used, and whether you made a good job of the painting last time. However, as a guide, you should work on the assumption that you’ll need to repaint your exterior windowsills every 5 – 15 years.
What are the best weather conditions for painting windowsills?
Dry and warm, but out of direct sunlight. Exterior painting is usually done between April and September.
What tools do I need for painting outside windowsills?
A scraper, a dust brush, sandpaper, and a paint brush are the only tools you need for painting exterior windowsills. You might need a couple of dust sheets too.
How many coats of paint should I apply to exterior windowsills?
Two coats of paint are generally all you need.
Final Thoughts
I think that’s everything on painting exterior windowsills. We’ve covered prep, primer, and the best paint. Stick with everything I have said, and you can’t go wrong. Not just in the short term, but you’ll get that long-lasting finish.
Great post, thanks. Whats the finish like with Zinsser compared to the water based ones ?