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How To Apply Concrete Floor Sealers

indoor sports facilities with clear floor coating

Proper application is crucial for the effectiveness and longevity of the concrete floor sealer. Follow these steps for a successful application:

Preparing the Concrete Floor

Thoroughly clean the floor to remove any dirt, dust, or stains. This step is essential as any debris left on the surface will prevent the sealer adhering to the concrete substrate. Use a broom, vacuum cleaner, or mop to ensure the floor is free from any loose particles. For stubborn stains, you may need to use a specialized concrete cleaner or degreaser such as Polycote Etch IT or Degrease IT.

Repairing holes and cracks

Repair any cracks or imperfections in the concrete before applying the sealer. Cracks can compromise the effectiveness of the sealer and allow moisture to seep through, leading to potential damage. Fill in the cracks with a suitable low viscosity resin such as Crackfiller EP100. Fine blemishes and small holes can be filled with products such a Easi-fil which can be trowelled super smooth and will dry in less than 30 minutes.  Finally for larger holes, where maybe you might have impact damage or where bolts have been removed from the floor, products such as Cretex EP will prove to be quick and easy to use.

Allow any or crack fillers or patching compounds to dry completely before applying the sealer coat.

Ensure substrate is as dry as possible

First and foremost, if you are intending to use a solvent based sealers such as Flortex PU, it is crucial to ensure that the concrete floor is completely dry.  Solvent based products will not adhere to damp surfaces.

Water based sealers such as Flortex Clearseal will indeed adhere to damp surfaces, but we still strongly advise to have the floor a dry as possible and the reason for this is very simple:  If the floor is wet, the pores or the concrete are ‘filled’ with water and thus, the chosen primer will achieve little to no penetration of the substrate. The coating will prove to provide a far better seal and be far longer lasting if it is allowed to penetrate and ‘lock’ well into the substrate. Apart from this, any moisture left on the surface prior to application of the sealer may well result in an uneven finish as well as a poor or even non-cure situation.

If any water or dampness has been in the area, it is always advised to allow the surface to air dry for at least 24 hours. Of course, heaters, dehumidifiers or fans can help speed up the drying process.

Preparing the surface

If necessary, etch the surface to ensure proper adhesion of the sealer. Etching involves using an acid-based solution such as Polycote Etch IT to remove the weak laitance and dust.  It is important to achieve a clean solid surface.  The etching solution will also help create a keyed texture which then helps the sealer to penetrate and bond effectively to the substrate.

It is advised that you follow the manufacturer’s instructions carefully when etching the floor, as different sealers may require different etching methods.

Applying the Sealer

Follow the manufacturer’s instructions for the specific sealer you’re using. Different sealers may have different application methods and drying times. It is essential to read and understand the instructions BEFORE proceeding.

Use a roller or sprayer to apply an even coat of sealer, working in small sections. Start from one corner of the room and work your way towards the exit to avoid stepping on the freshly applied sealer. Ensure that the sealer is applied evenly and without any puddles or streaks.

It is important to apply enough primer to be able to penetrate the surface to not only seal the concrete but to allow a good bond. It is always advisable to apply an even coat as much as possible. However, you will almost always see some parts of the floor are more porous than others, and this will be displayed by a resultant patchiness where the sealer has soaked well into the substrate and in other parts where the concrete is more solid, it has coated nicely, leaving a nice even sheen.

In order to get an even sheen of the whole floor you may need to apply a second coat.  If this is necessary, wait for the first coat to dry completely BEFORE applying the second coat.  Indeed, should any further coats be required, allow the existing coat to cure before continuing with any further applications.

Avoid over-application and brush out any puddling of the sealer, as this may lead to a uneven or cloudy finish.

Curing and Drying Times

After applying the sealer, allow it to cure and dry according to the manufacturer’s instructions, before allowing use of the area. Remember that the curing and drying time can vary greatly depending on the environmental conditions as well as the type of sealer used.

To allow for the correct and sufficient curing times will ensure the sealer not only bonds effectively with the concrete but will also withstand the wear and tear of daily life and thus, provide long-lasting protection. It is crucial to follow the recommended curing time before subjecting the floor to regular use.

Hazards To Avoid When Sealing a Floor

Applying sealer too thin

When applying too thinly, often when persons are trying to cover an area as cheaply as possible, remember that you will have next to no penetration and the final coating will be very weak.  The longevity of even an expensive paint when applied to thinly will be hugely reduced!

Applying sealer too thick

There are several reasons why you should not apply too thickly.

  • If it is a water or solvent based product, and it is applied in a very thick coat, the top surface of the coating will begin to ‘skin’ over and thus the curing begins. However, the water (or solvent) this is within the coating itself then has to percolate through the surface skin in order for it too, to cure.  An easy way to understand this is if you imagine you have applied the paint onto the floor in the normal way and leave the remaining product in the tin next to the applied product AND with the lid off.

When you come in the following day, you will be able to walk of the finished floor.  The tin however, which is exactly the same paint in exactly the same environment will have simply skinned over and all the paint underneath will be as wet as the day before.  This is because the water or solvent is ‘trapped’ under the skin and therefore, as we have said earlier, it needs to penetrate through the skin before it can cure.

  • Applying to thickly may well result in the floor looking patchy rather than leaving a nice even finish.
  • When applying some products, particularly single pack polyurethanes, it is extremely important not to apply too thickly and leave too much of a surface build in a single coat. Even more importantly don’t allow the product to puddle in dips and depressions as the product has a tendency to ‘foam’ and thus can create an unsightly creamy, patchy appearance.  This is all very simply avoided by the applicator, by rolling or brushing out as necessary.
  • To thickly apply the coating can make the ultimate curing time exponentially longer, due mainly to the skinning process as explained clearly above.

Use of chemicals

No matter whether it is the use of basic cleaning chemicals or the possibility of more harsh chemicals spilling onto the floor from working processes, make sure it has the full curing time required as per the data sheet.  Full chemical resistance will not be reached until the said product has fully cured.

Water, Condensation, Dew Point.

The prevention of water before the product has at least initially cured is no different than that as stated above for chemicals.  Obviously not quite so important BUT, do not allow the floor to get wet until at least after the initial curing period, often a minimum of 24 hours.

High humidity levels and/or condensation dripping down onto the floor can cause an uncured sealer to ‘bloom’ thus causing an unsightly whiteness to the surface.  Whilst it is obvious that water contamination during the curing process should be avoided if at all possible, if it is only a small amount of condensation/water, this discolouration does not normally have too much of an ill-effect and will, in many cases, actually ‘wear off’ over a period of time.  However, if the coating is subjected to too much surface water, and in the worst case scenario, this can result in a poor or even non-cure situation.

Mixing and Pot-Life

If you have decided to use a twin pack resin sealer, make certain that the product is mixed in the accurate proportions.

Mixed materials will then have a pot life that can be anywhere from 5 minutes to 2 hours.  The pot life is mostly dictated by the ultimate curing time of the said product.  The faster the curing time, the shorter the pot life. The pot life being the period of time you have to apply, before the coating goes too hard!

Please consult with the manufacturer’s product data sheets BEFORE mixing.

Finally, and for obvious reasons, don’t mix more material than what you can apply within the given (pot-life) time.

Maintenance of Your Floor


Regular maintenance is essential to ensure the longevity of your sealed concrete floor. Sweep or vacuum the floor regularly to remove any dirt or debris that may cause scratches or wear down the sealer. Avoid using harsh cleaning chemicals or abrasive tools that can damage the sealer. Instead, use a pH-neutral cleaner specifically designed for sealed concrete floors.

Periodically check the condition of the sealer and reapply as needed. Over time, the sealer may wear off in high-traffic areas or become less effective. Look for signs of wear, such as water absorption or a dull appearance. If necessary, clean the floor thoroughly and reapply the sealer according to the manufacturer’s instructions.

By following these steps and implementing proper maintenance, you can ensure that your concrete floor sealer remains effective and provides long-lasting protection. Enjoy the benefits of a beautiful, well-maintained concrete floor for years to come.

Related Articles

A Comprehensive Guide to Different Types of Concrete Floor Sealers

Understanding the Different Requirements of a Concrete Floor Sealer

Factors to Consider When Choosing a Concrete Floor Sealer

Thank You

Polycote UK would like to take the opportunity to thank you for taking an interest in these product and application articles and hope they have been some help to you.

We would of course be pleased to answer any specific questions should you wish to contact us directly on 01234 846400 or email: help@polycote.com



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