One part of the home that benefits from waterproofing is the roof deck, quite obviously because it gets a lot of direct contact with water whenever it rains. If you have a roof deck and have not taken waterproofing measures, take this as a sign to do something about it. Here’s your guide to waterproofing a roof deck with Boysen Plexibond.

Step 1: Surface Preparation

If you’re working on a new surface, you will need to wait 14 to 28 days for your concrete to cure. Remember, Boysen Plexibond can only be applied on a bare surface that has not been previously painted. If it happens that your surface already has paint on it, it should be completely scraped off.

Clean your surface. It should be free from oil, grease, dust, dirt, and any loose grit or mortar.

Then, dampen the entire area. This will help keep your Plexibond layer, when you’re applying it already, from drying too fast causing it to crack and break. Don’t forget to do this as you’re working on a roof deck where the conditions can be especially hot and sunny.

How-to Guide: Waterproofing Your Roof Deck with Boysen Plexibond | MyBoysen

Step 2: Boysen Plexibond and Fiberglass Matting

Prepare your Boysen Plexibond mixture by slowly mixing 6.5 kg cement to 4 liters Plexibond. Although you can do this by hand, the job is made easier with a machine like a power mixer because you want to make sure you don’t get any lumps.

Keep in mind that the pot life of the resulting mixture is only 2 hours. So, only mix what you can use to avoid wasting product. While you’re working, stir as often as you can to avoid settling.

Now that you have your mixture, you will need to apply 3 to 6 coats by brush for a smooth finish or 2 to 3 coats with a textured roller for a textured finish.

After the second coat, while the Plexibond mixture you applied is still wet, place fiberglass matting on areas susceptible to cracking or movement like joints, corners, and active cracks. Make sure the Plexibond coating and the matting are completely dry before applying the next coats.

When all the coats have been applied, let the area dry for a day.

How-to Guide: Waterproofing Your Roof Deck with Boysen Plexibond | MyBoysen

Step 3: Bond Coat and Concrete Topping

After the drying period, apply one coat of just pure Boysen Plexibond straight from the can. This time around, do not add anything to it. This is called the bond coat.

While this bond coat layer is still tacky or sticky, apply a mortar or concrete topping. Boysen Plexibond cannot be left exposed on its own to the elements so a topping is crucial. If you don’t do so, your Plexibond will deteriorate faster than it should.

Step 4: Paint

For beautification and extra protection, you can also choose to install tiles or apply paint on top of the concrete topping.

For paint, we recommend Boysen Acqua Epoxy as it can be used on concrete floors such as roof decks. With excellent durability, Acqua Epoxy is solvent-, chemical-, and stain-resistant. It has good gloss retention and UV resistance as well. Because it’s water-based, it’s also easier to work with than solvent-based paint products.

Just like how you followed the painting guide for Plexibond, apply Acqua Epoxy per recommendations too. Find details on how to do so here.

Getting Additional Help

Using Plexibond on vertical surfaces is already complicated enough, using it to waterproof a roof deck raises the difficulty even more. If you don’t have a lot of experience with Plexibond yet, it may be best not to DIY this project. Getting a professional painter to do the job for you is a smart move.

If you have other questions on Plexibond, feel free to reach out to our Technical Department. Email or call (02) 8363-9738 local 413 to 418 during office hours for a one-on-one consultation.


Jill is a writer on a continuous journey to learn about paint and share them with you, the reader. She has an interest in the technical side of things but also thoroughly enjoys playing with colors. She likes calm greens, quiet blues, and mellow yellows best.

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