Thompson’s Water Seal is a transparent, water-based waterproofing agent formulated to deeply penetrate the dry, porous exterior substrates to prevent ingress of moisture.
With the increasing popularity of the product, many users want to know if they can paint over the sealer. Or if the sealer can itself be put over other finishes such as paints or stains.
The answer to the first is a firm No, you shouldn’t try and waste your time painting or staining over Thompson’s Water Sealer.
According to Thompson’s official website, “the hydrophobic properties of the Water Seal will negatively affect the adhesion of any paint applied over it.” So if you go and paint over it, the paint will not adhere properly, can cause runs or sagging, and is likely to peel.
The answer to the second question is a bit more nuanced. And I will try to cover this in my article later. But first, let’s start with a few details you should know. So, let’s jump into…
Why Use Thompson’s Water Seal?
Thompson’s Water seal is a high-performance transparent water-repellent formula that works on numerous building materials, including brickwork, wood, and concrete.
Its formulation includes a silicone micro-emulsion that helps to prevent water penetration and also the problems due to “freeze-thawing,” which can break down the structure.
The sealer is designed to be used outdoors and not indoors. Particularly on wooden surfaces like decks, patios, porches, and roofs, where it can last longer than other standard waterproofers while continuing to repel moisture.
The excellent water-repelling properties of the product help in preventing water damage long after other products have begun to fail.
Assuming you have adhered to all the application instructions and guidelines provided by the manufacturer, one coat of Thompson’s Water Seal will typically last 3-5 years on horizontal surfaces and 5-7 years on vertical surfaces.
That said, it is recommended to reapply the sealer every few years to maintain optimal protection, even if no visible signs of wear or tear are present.
Now that we’ve got a good understanding of the product and why it’s so popular, let’s try answering our main questions…
Painting Over Thompson’s Water Seal
There’s nothing harm in thinking about making your project look even better with a fresh coat of paint color on the sealed surface.
But should you really try this with Thompson’s Water seal? Is this actually doable? And on what surfaces can you try it?
Well, if you desire to, this can be done. But you should only paint over Thompson’s Water Seal after you have waited for at least 45 days after sealing the surface. This is because it will take that long for the sealer to completely cure.
Even after 45 days, you should check the surface to make sure it is completely dry before painting. The best way to test for this is to pour a bit of water on the surface.
If the water beads up, you know the surface is still curing, and you should wait a bit longer. However, if the water soaks in, the surface is ready for paint.
But What TWS Sealed Surfaces Can You Paint – Why and How?
Assuming you are ready to wait for 45 days to cure the sealer, you should still keep in mind that you can only paint over concrete with Thompson’s Water Seal (TWS) Clear Masonry Protector Waterproofer.
Surfaces like wood are not the right candidates for painting over the sealer unless you plan to remove the water sealant altogether by scrubbing or sanding the wood surface.
For cement and concrete, it’s not enough to just put up any old concrete paint on top of the sealer. Instead, you should be prepared to apply the paint correctly to the surface, which might need good time and effort.
Here are the steps you would generally need to follow when putting up paint over Thompson’s Water Sealed concrete…
- Start with a clean masonry surface that is free of any dirt, debris, or grease. Use a pressure washer if required.
- Use a concrete etcher to roughen up the surface and help the paint to adhere better.
- Rinse off the surface with clean water and let it dry completely.
- Apply a coat of primer designed for use on concrete.
- After the primer is dry, apply your chosen paint in thin and even coats.
- Let the paint dry completely between each coat.
- Apply a clear sealer over the paint to help protect it from wear and tear.
If the sealer is old and you want to remove the water seal from the concrete before painting, the sandblasting kit is a handy tool that can help. While it might be a little extra work but it generally works great.
If you plan to apply paint on a wooden surface that’s sealed with TWS, use a wood stripper solution or a power sander to remove the sealer first. Once the surface is bare, follow the regular process of painting the wood.
A word of caution – Thompson’s Water Seal AdvancedClear is not paintable. So, you can’t paint over it, irrespective of the surface.
Using Thompson’s Water Seal On Top Of Painted Surfaces
According to Thompson’s website, the answer is a resounding no.
This is due to the fact that the water seal may not adhere securely to the paint, which may eventually result in paint seeping from under the seal and/or paint failure.
The same goes for applying a water seal over any type of wood stain, oil, or varnish.
Especially if you plan to add the water seal onto the oil-based paints, stains, and finishes – it is best to follow the manufacturer’s instructions to avoid any issues that may arise from not doing so.
Thompson’s Water Seal problems generally include sealant not drying, a sticky surface for a long, a tacky feeling, a bad odor, and so on. If you come across any of these problems, you can prevent/fix them by following the below-mentioned tips.
- Apply the sealer in thin coats as per the instructions.
- If you have applied it too thickly, wait for the first coat to dry off completely, and then sand the surface lightly before applying the second coat.
- Ensure good ventilation while the sealer is drying.
- Avoid using fans, as they might end up blowing dust onto the wet surface.
- Keep children and pets away from the area while the sealer is drying.
- If the surface still feels tacky even after 24 hours, apply a thin coat of mineral oil.
If you come across any bad odor, it is generally because of the VOCs present in the sealer. Although it’s not very high, it can still cause some problems for people who are sensitive.
Generally, the smell should dissipate within a few days, but if it doesn’t, you can try using a ventilation mask while the sealer is drying.
The Bottom Line
While it’s not recommended in the first place, painting over Thompson’s Water Seal is doable. If you plan to, you should only attempt it on concrete surfaces (and not wood) that have cured for at least 45 days.
Putting TWS on the finished painted surface, however, should not be done as it can cause paint failure and various other sealant problems that can be hard to fix.
Moreover, trying to accomplish any of the two processes will only be too much work for you because the prepping time is high, and not all surfaces are compatible. So, in my opinion, it is best to avoid using water sealant on the painted surfaces altogether and vice versa.
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Jack Luis is a semi-retired painter who loved painting his clients’ ideas on their walls.
He had worked as a painter for more than a decade to serve the customers in areas such as Charleston, Mount Pleasant, Beaufort, Georgetown, SC (South Carolina). Today in his free time, he likes to read and write about the newer techniques that are being implemented in his profession. You may read more about him here or get in touch with him here.
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