There are several reasons you should know how to seal concrete floor with PVA – to keep down the dust, provide a waterproof seal, and give a bond for a finishing layer of paint, tile, or screed.
I once helped a friend convert a garage into a guest room. The first thing we had to do was remove all the oil and grease spilt over the years. We also had to remove all the paint splashes from the countless tins of paint stirred and mixed there. This task is not something I want to do again, and you can prevent much of this work by sealing the concrete floor with PVA.
So if you want to know how to seal a concrete floor with PVA, read on.
Why Seal a Concrete Floor?
Concrete, especially when freshly laid, leaves a layer of cement dust on the surface, which continues to appear long after the initial layer brushes away. So, the main reason for sealing a concrete floor is to hold in the dust.
The second reason for sealing a concrete floor is to reduce the porosity of the concrete so that you can paint it or provide a bonding coat for other finishes.
One of the best products for sealing a concrete floor is PVA.
What is PVA?
PVA, or polyvinyl acetate, is an odourless resin that’s white when applied but dries colourless. PVA has a high bonding strength, so builders use it as a bonding agent in many applications, including wood glue.
Isn’t SBR Better?
SBR, or styrene-butadiene rubber, is similar to PVA in that it seals and helps bond with subsequent finishes – paint, tiles, laminate, etc. – but the difference is that SBR is water-resistant when it dries out. PVA is, therefore, better if you want a product that remains soluble and allows the substrate to breathe.
In the case of a newly laid concrete floor, it can take up to 3 months for the concrete to dry out, depending on the concrete thickness and weather conditions. Therefore, you shouldn’t apply anything to seal the moisture during this drying period.
That said, PVA is not hard-wearing, and because it remains water-soluble, it’s not suitable for use on its own where it’s subject to foot traffic and heavy rain. In these situations, builders apply a layer of paint over the PVA. If you want to know more about floor painting, our guide to the different types of paint includes a section about concrete floor paint.
Tools & Materials
The tools & materials you need depend on the condition of your floor and the amount of preparation required, but for a newly laid concrete floor, you will need:
- PVA primer-sealer – 1-5 litres depending on the area to be covered.
- Vacuum cleaner – don’t use your best one!
- Bucket for mixing – 5 litres should be big enough.
- Brush or roller for applying – a yard brush will do but not too stiff.
For older concrete floors, you may also need:
- Paint stripper.
- Cement/sand concrete repair kit.
- Trowel to apply filler.
- Scraper to remove paint and other solid substances.
- Trisodium phosphate (TSP).
Health and Safety Measures
Chemicals like TSP and paint stripper can cause burns when mixing, so wearing the right PPE is essential. I.e. wear rubber gloves and goggles/glasses to protect the eyes and skin. Also, always mix products such as this in a well-ventilated area.
How to Seal Concrete Floor with PVA – Step-by-Step Instructions
OK, got everything? Off we go.
Step 1 – Prepare the Concrete Floor
If it’s a new floor, this might simply involve sweeping away dust, but it’s better to use a vacuum cleaner.
You will probably have to remove paint, greasy deposits, bits of cement, and other solids that might have spilt over the years for older floors. You may also need to remove broken bits of concrete and fill in any holes with a sand/cement mix.
Allow any patching to dry before proceeding.
Step 2 – Thoroughly Clean the Concrete
You may skip this stage if it’s a new floor, free from oil and grease.
Prepare a solution of 15g TSP to 1 litre of water; this will cover around 10m2, depending on how smooth the floor is.
Pour the solution onto the concrete floor and brush it into the surface. Allow at least 10 minutes to dissolve any oily substances, and then wash down using tap water, ideally with a hose and a brush.
Step 3 – Apply the PVA
Mix a solution of one part PVA to four parts water in a bucket and stir. Only mix what you can use for each coat; as a guide, a 1:4 mix will cover 24 to 56 m2/litre, depending on the porosity of the concrete.
Apply one coat of the solution and allow it to dry – that should take about 8-10 hours. The milky-white liquid becomes clear when it’s thoroughly dried out.
You can apply the solution with a brush or a roller; the result will be the same but use one with a long handle to apply it standing.
Step 4 – Apply the Finishing Coat
This mix should be thicker to make it harder-wearing. The ratio varies between manufacturers, but use one part PVA to 3 parts water as a general rule.
Using the same coverage rates as Step 3, this should cover 18 to 42 m2/litre, but it’s more likely to be at the higher end because the surface is less porous after the first coat.
How to Seal Concrete Floor with PVA – Final Thoughts
One thing about PVA is that it’s incredibly versatile and comes in handy for many jobs around the house, including use as an adhesive. So don’t worry if you have a lot leftover – you will find a use for it.
If you’re still in doubt, this video by Crafty Camel illustrates how to prepare and seal a concrete floor. Don’t pay too much attention to the quantities; this depends on the porosity and the product used.
P.S. PVA is also great for plastering walls. Check out our guide to using PVA for plastering to learn more.