Sealing a concrete floor is a crucial step towards ensuring it remains strong and in great condition for years to come. There are a plethora of benefits to using sealer on concrete — and it’s almost effortless to apply. So, what are you waiting for? Start applying sealer to your concrete floor today. Check out our article to find out how to prepare and how to seal a concrete floor. Need concrete for your project? Call our team on 0800 859 5371 to place your order!

Why is sealing a concrete floor important?

Sealing concrete is one of the most important aspects of concrete floor installation due to the wealth of benefits it provides. Concrete sealers protect your concrete from:

  • Weather exposure
  • Water
  • Oil
  • Grease
  • Staining
  • Abrasion
  • De-icing salts

But sealers offer more than just protection. They also improve concrete floors by:

  • Improving durability
  • Inhibiting mould
  • Extending their lifespan
  • Maintaining their colour

What you need:

  • Putty knife
  • Degreaser
  • Wet mop
  • Pressure washer (for outdoor use)
  • Concrete filler

Overall, your concrete flooring will enjoy so many benefits with just a simple application. All you need to do is learn how to prepare your concrete for the sealer and how to apply it. How to seal a concrete floor

How to prepare your concrete for sealing

Before you can apply the sealer, you need to prepare the concrete. It’s important not to skip this step; preparing the concrete will make sure that the floor is properly sealed. Follow these steps to prepare your concrete:

  • 1. Remove everything from the floor that you wish to seal
  • 2. Using a putty knife, remove the skirting boards from the wall
  • 3. Remove any debris that remains on the floor
  • 4. Use a degreasing product to degrease the floors
  • 5. Scrub any oily areas of your floor with a wire brush
  • 6. Use a wet mop to rinse your concrete
  • 7. Wait until the floor is completely dry
  • 8. Fill any cracks in the concrete using concrete filler

If you are wanting to seal a concrete floor outside, follow the same steps above – however for #2, consider the environment around the concrete. Make sure to clean up any oil or debris properly, instead of letting it drain into the grass or soil. Also consider putting a sheet over any grass or soil, to avoid run off.

How to seal your concrete floor

  • 1. Strip any existing sealer from the surface
  • 2. Use an etching solution to open up the concrete
  • 3. Apply a thin coat of the sealer using either a sprayer or roller
  • 4. Leave the first layer of sealer to dry
  • 5. Apply a second coat of sealer in the opposite direction to the first
  • 6. Wait for the sealer to dry fully before applying any pressure onto it

For the best results, always use a sealer and quality concrete mix. At Total Concrete, we mix and deliver the perfect concrete blend for your needs. So whether you’re a domestic user installing a small concrete floor or a commercial user building the foundations for a house, we have the concrete for you. We deliver throughout Woking, Surrey, Guildford and the surrounding areas, and pride ourselves on our quick turnarounds. Contact us today to get your hands on a high-quality concrete mix, call us on 0800 859 5371 to place your order.

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  3. How to Seal a Concrete Floor From Moisture

Have you noticed water seeping through concrete floors in your home? Is your garage or basement floor damp? If so, the concrete foundation of your home or garage may be in danger. The good news? Preventing damage could be as simple as sealing your floors. Read on to learn how to seal concrete floors from moisture.

First, Why Seal Concrete?

Water seeping through concrete floors in a basement or garage leaves your home susceptible to big problems. This water can affect the structural integrity of your home and be a catalyst for unhealthy mold and mildew growth. Over time, with constant exposure to moisture, a small crack in a concrete wall can morph into a big problem, allowing insects and the elements into your house. Sealing your home’s concrete surfaces is an important type of preventative maintenance. Taking care of your home’s concrete before you have a problem (or larger problem) is key to maintaining your home’s indoor air quality and foundational integrity.

How to Seal Concrete (the Right Way)

There are four key steps to sealing a cement surface like a garage or basement floor the right way: 1) selecting the appropriate sealant, 2) cleaning the surface, 3) fixing cracks, and 4) sealant application. Follow the instructions below for a quality seal:

  1. Pick Out Your Concrete Sealer – There are a variety of sealers, so it’s important to select the one that’s best for your project. Here are the options available for concrete surfaces:
    • Acrylic sealer – This easy-to-apply sealer is best for basements and other concrete floors that will not come into contact with oil or grease. Acrylic sealer sits on top of the concrete instead of seeping in, which makes it ideal for sealing interior floors.
    • Epoxy sealer – More durable than acrylic, this type of sealant protects against grease and oil, and is perfect for a basement, garage or outdoor shed. There are also a few color varieties so you can select your own finish.
    • Polyurethane sealer – This type of sealer has a more durable finish than acrylic and epoxy sealer, and it also has UV protection. It’s often used as an overcoat for an epoxy sealer in interior indoor concrete surfaces.
    • Siloxane sealer – Lasting for up to 20 years, this sealer penetrates concrete for top protection. This is a common sealant for indoor and outdoor surfaces such as driveways, patios and garages.
  2. Clean Your Floors

Make sure you take the time to thoroughly clean your concrete floors (or walls) to ensure they’re ready to be sealed. Here are the steps:

  • Move all items out of the area.
  • Sweep all dirt, dust and debris away with a broom.
  • Remove oil, grease, paint and any other stains that may be on your concrete floors. To clean your floors, spray or pour a concrete cleaner onto the floor and use a scrubbing brush or broom (depending on how large the surface area is) to rub it into the concrete.
  • Use a hose to rinse the cleaner off the concrete. Be sure to make a plan for drying or draining the floor surface after rinsing.
  • Let your concrete fully dry for 24 hours.
  1. Fill in Any Cracks

After your floors are clean and dry, locate any cracks or holes in your concrete. Repair them by applying concrete repair caulk and using a towel or washable cloth to smooth it out. Let the caulk dry according to the manufacturer’s instructions.

  1. Apply Concrete Floor Sealant – Once you‘ve selected your sealant and fully prepped your surface, you’re ready to apply the sealant. Here are the steps to successfully apply sealant to your concrete surface (two coats are recommended):
    • Make sure windows are open and the area is properly ventilated.
    • Apply the sealant with a 9″ roller. Use a paintbrush to cut-in, ensuring the corners and edges are properly sealed.
    • Let the sealant dry. Make sure to view your sealant directions for recommended drying time. Depending on your sealant, the waiting time can be between two hours and two days.
    • Apply a second coat of sealant using both the roller and brush.
    • Let the final coat of sealant set for three to four days, or the recommended time on the manufacturer’s instructions, before returning all the items onto the floor.

Choose Rainbow Restoration for Hard Surface Cleaning & Water Damage Cleanup

Have you inherited a seeping concrete floor? Has your home been overwhelmed by a flood? Rainbow Restoration Restoration is here to help. Our IICRC-certified technicians specialize in hard surface cleaning and water damage restoration services designed to leave your home clean, dry and stain-free. Give us a call at (855) 724-6269 or request an appointment online to get started today. Build the ultimate DIY concrete patio with these instructions from Mr. Handyman. Like Rainbow Restoration, Mr. Handyman is a part of the Neighborly® community of trusted home service brands. how to seal and dustproof an internal concrete floor This article explains how to seal and dustproof a concrete floor, along with other interior walls, or work surfaces cast in concrete. The content of the guide relates to sealing and dust-proofing interior concrete floors. There is further information regarding using impregnating sealers (also known as subsurface sealers). Whilst impregnating sealers do not dustproof, they can have some advantages when sealing wet areas.

Which product should I use to seal & dustproof concrete floors?

We recommend using Floorseal Concrete Floor Sealer to seal & dustproof interior concrete floors. Floorseal Concrete Floor Sealer can be applied to concretes within 28 days of pouring & drying. This sealer is to be applied in 2 consecutive coats with 1 hour of drying time between coats. The sealer will accept light foot traffic within 1 hour of each coat. Floorseal Concrete Floor Sealer is a water-based sealer, free from solvents & VOCs so easy to work with. This concrete sealer dries rapidly with little associated odour. The sealer will penetrate the pores of the concrete, partially drying on the surface and therefore is capable of fully dust proofing the concrete.

What kind of concrete can I seal Floorseal Concrete Floor Sealer with?

You can seal most kinds of concrete with our Concrete Floor Sealer including anhydrite screeds. It does not matter if the concrete is new or old or the level of porosity. If the concrete is porous, it is possible to seal it with Floorseal Concrete Floor Sealer. The only kind of concrete we do not recommend using this sealer on is a fully polished concrete. Fully polished concretes have a mirror-like reflective finish, usually polished up to 3000 grit. This will have been carried out with either a high-speed polishing machine or a machine with a huge amount of weight. Concretes which have been diamond ground and honed up to a matt or satin finish are suitable to seal with our concrete sealer. Polished concretes are obvious as they have a highly reflective mirror like finish, similar to polished marble or granite. If your concrete is totally matt or has a satin/low sheen finish it is suitable for sealing with Floorseal Concrete Floor Sealer. seal and dustproof garage concrete floors

Can I seal my garage floor with Floorseal Concrete Floor Sealer?

Yes, this product is perfect for sealing concrete garage floors. The concrete sealer will reduce the porosity of the concrete and dustproof the floor. It can be applied to new concrete and older concrete floors. We recommend cleaning the floor with an intensive non-acidic cleaning agent before sealing older floors. This will help break down dirt, grime, and oils, so the sealer can penetrate and adhere to the surface. Please use Floorseal Stone Floor Cleaner to do this. Stone Floor Cleaner is an alkaline solution so will not attack the concrete. You will need to rinse the floor with clean water after using Stone Floor Cleaner and allow at least 24 hours of drying time after cleaning. Never seal a concrete floor with a dustproofing sealer if it is clearly damp.

Sealing power floated concrete floors

There is no real difference between sealing a power floated floor rather than an older floor. Power floated floors are likely to be found in buildings which may become a workshop, industrial units, or office spaces. Floorseal Concrete Floor Sealer can be used to seal a power floated floor in 2 coats as per normal application instructions. You must leave the floor to cure for approximately 28 days before sealing. It is unlikely that you would need to clean a power floated floor. But it is worth removing any general dust left from the general construction process of the building and floor. If your floor has a large amount of surface tension and water/liquid will not penetrate it all you may have to etch the floor to break this tension.

How does Concrete Floor Sealer work?

It is a water-based white liquid which is applied to the surface with a roller, paint pad or brush. It could also be applied by microfibre flat mop or cloth. Once the first thin coat has been applied, the 2nd coat will adhere easily to the first. You will notice that more product is required during the 1st application than the 2nd. The sealer dries to a totally clear low sheen (almost matt) finish. You can apply more than 2 coats if required, but make sure they are applied in even thin coats, avoiding pooling and puddling. Floorseal Concrete Floor Sealer can also be used as a priming agent before painting the floor. We recommend using a quality floor paint to do this such as a 2-part epoxy paint. The sealer can also be used as a primer if a micro-topping is to be applied later. If you wish to use this product as a simple primer you will probably only require 1 coat.

How do I apply Floorseal Concrete Floor Sealer?

There are full instructions on the Technical Data Sheet which you can download or read on the actual product page. But as a quick guide:-

  • Only apply to dry fully cured surfaces.
  • Test in an inconspicuous place, if not suitable do not continue to use.
  • Remove previous sealers or oils etc.
  • Apply in 2 consecutive thin coats approximately 1 hour apart.
  • Use a roller, paint pad or brush to apply.
  • Avoid pooling or puddling, thin coats are best!

The product is a water-based, low odour and rapid drying product which seals and dustproofs, it is very easy to apply. Microfibre flat mops produce very thin, even coats with less chance of application errors or marks. Once the first coat has been applied to any type of floor the 2nd coat is much easier to apply.

What kind of finish does Concrete Floor Sealer produce?

This product will dry to a very low sheen (almost matt) finish. If the concrete is highly porous it will require more product, the finish will still be no more than a low sheen. On harder dense concretes you may see a little more of a sheen. This product will not produce a gloss finish. We recommend testing any sealer before use, so you know are happy with the finish. The various types of concrete and levels of porosity within individual concretes all play a part in the final overall finish. It is worth checking before fully applying any sealer to a whole floor, we supply samples, so it is easy to do this!

Do I need to etch the surface of the concrete before sealing concrete?

Generally, no you do not need to etch the surface of the concrete before sealing with Floorseal Concrete Floor Sealer. Unless you have sealed the concrete before with an impregnating sealer, or if the floor is heavily ingrained with dirt or oil. Contact us first if you think you need to do this. Etching means slightly disrupting the surface, so it becomes more porous. Most concretes are porous enough without the need for etching. Contact us first if you think you need to etch the surface. The removal of previous sealers is important, this means stripping the sealer or breaking it down. Please contact us if you need to remove a previous sealer etc.

Coverage Rates

Concrete Floor Sealer will cover approximately 10m2 per coat. Please be aware that coverage rates always vary depending on the individual porosity of the concrete being sealed. You will not use as much product on the 2nd coat as on the 1st coat, particularly when applying with microfibre mop systems. Sealed and protected concrete floors are a stunning modern flooring option

In conclusion

Floorseal Concrete Floor Sealer is suitable for most interior concretes where the surface is to be sealed and dustproofed and works for both floors and walls. It is low odour, rapid drying and contains no solvents or VOCs. It is probably the best and easiest way of sealing an interior concrete floor. You can use this product to seal anhydrite screeds or other porous screeds but always check before use. Apply Concrete Floor Sealer in 2 thin coats, approximately one hour apart.

Fully Wet areas i.e. wet rooms

We do not recommend sealing a full wet area with a dustproofer i.e. a wet room. You will need to use an impregnator to seal a fully wet area. Floorseal Premium Impregnating Sealer can be used to seal wet areas but it will NOT dustproof. Very porous concretes or screeds should not be used to create fully wet areas due to the difficulty created in sealing them. An impregnator is more appropriate for sealing fully wet areas when the concrete is of an average to low porosity.

Removing rust from concrete

To remove rust from concrete please use Rust Remover for Stone. It is a non-acidic cleaning solution which can be used on concretes. But please test before use, particularly on coloured concretes. This rust remover will erase surface rust spotting etc. It should be applied and rinsed off after use. It is possible to use impregnating sealers to seal concrete which has some benefits. As previously mentioned they can be used to seal fully wet areas, or used as a pre-sealer before applying a dust proofer. Pre-sealing, before applying a dustproofer, is an advanced technique and beyond the scope of this article. We recommend contacting us if you wish to pre-seal concrete before applying a dust proofer. Please note that impregnating sealers do NOT dustproof concrete so are not discussed in detail within this article. Further information Please Click Here to view all our products & accessories for cleaning and sealing concrete. This includes all our handy ‘how to’ guides for cleaning and sealing interior and exterior concrete. The information included in this article is not exhaustive. If you need further information please contact Floorseal on (01484) 861461 or email us [email protected] our web address is Ribbon Pattern Concrete Floors Cornerstone Concrete Designs Orrville, OH Cornerstone Concrete Designs in Orrville, OH No decorative concrete floor installation is complete without the application of a sealer. Taking the time to put down this final layer of protection not only prolongs the life of your floor, but can also enhance and preserve its appearance. Here’s a list of common questions about concrete sealers and how they work to protect your floor. Find concrete floor sealing contractors near me


A concrete floor sealer will beautify and preserve your floor. Sealing brings out the beauty of a concrete floor by enhancing the color and adding sheen. Sealing also preserves the decorative treatment by protecting the concrete surface from abrasions and stains. Some floor sealers form a protective film on the surface of the concrete, while others penetrate into the floor.


Many people opt for having their floors professionally sealed. But, if you are thinking of doing it yourself, here are the steps for sealing concrete floors:

  1. Allow recently poured concrete to cure fully
  2. Let stains or overlays dry thoroughly before sealing
  3. Remove baseboards or cover them for protection
  4. Clean the floor and wait for it to dry
  5. Wear protective gear and clothing
  6. Open doors and windows for proper ventilation
  7. Apply a thin coat of concrete floor sealer and let dry
  8. Apply a second coat in the other direction, let dry
  9. Wax the surface of the floor to prolong the life of the sealer
  10. Reapply the sacrificial wax as it wears off
  11. Reseal your concrete floor every few years

Is it better to roll or spray concrete floor sealer?

Most professionals agree that spraying sealer produces more consistent coverage. Plus sprayers are faster and more efficient for covering a large floor. Many contractors use a combination of spraying and back rolling to work the sealer into the floor and improve adhesion. Make sure the roller you use won’t shed lint into the sealer during application. Always check to see if the sealer manufacturer recommends a specific application tool.


Film-forming sealers (those that form a protective film on the concrete surface) are the type most often used for interior decorative concrete work. In the category of film formers, however, you’ll find several different types, each with advantages and limitations. Learn more about the types of sealer. Shop for Concrete Floor Sealers

Is the sealer compatible with my decorative treatment?

What will the sealer be applied to? Stained concrete, a floor overlay, a polished and dyed floor? Be sure to check with the sealer manufacturer to verify the compatibility of its product with the decorative surface it will be put on. Some sealers may interact with certain overlays or coloring agents, resulting in unwanted side effects such as blistering, bubbling, or bleeding.

Which sealers will protect my floor from scuffs or stains?

For a decorative interior floor, a high-build sealer with good resistance to scuffs and staining, such as a polyurethane or epoxy, will generally provide the best protection and be easier to maintain, especially in a high-traffic retail environment. Softer acrylic sealers usually require regular maintenance with several coats of a sacrificial floor finish, or wax, to prevent wear and black heel marks. View this comparison chart of concrete sealers.

Are concrete sealer fumes toxic?

When working indoors, it’s usually safer to use a water-based rather than solvent-based sealer, especially if the area can’t be ventilated. Solvent-based concrete sealers are extremely flammable and the toxic fumes they emit can be hazardous to breathe. They also may contain volatile VOCs. Learn more about checking the VOC content.

How do I know which sealer will provide the right sheen that I want on my floor?

If you’re after the look of polished marble, choose a sealer with a medium- to high-gloss sheen. Most acrylic sealers are available in a range of sheen levels. For applications where a high shine is not desirable, you can also find film-forming sealers with matte or low-gloss finishes.

Will sealing make my floors slippery?

Film-forming sealers may be slippery, especially in areas where water is present, like kitchens and bathrooms. Consider using grit additives that can be mixed into the sealer to improve traction. Read more in How to Make Concrete Non-Slip.

How long will the sealer last on my floor?

The life span of a sealer depends on exposure conditions and how well the floor is maintained. Epoxies and urethanes deliver the best long-term performance and can last years before the need for reapplication. When it comes to sealers, you get what you pay for, says technical expert Chris Sullivan. Avoid the temptation to pinch pennies. You don’t want a protective finish that will wear away after only a year or so. See Sullivan’s advice on sealer selection. Floor Sealer Videos Why Use a Sealer on Your Concrete Floor?
Time: 01:30
Using a sealer on your new concrete floor prevents a variety of costly problems from occuring. Sealing Your New Concrete Floors
Time: 01:49
Find out when sealer should be applied and how to select the right sealer for your new floor.


Decorative concrete expert, and vice president of sales and marketing with ChemSystems Inc, Chris Sullivan, provides in-depth answers to common problems associated with sealing concrete floors.

Cause of dull spots in sealed floor

Question: Four years ago I covered my basement floor with a patterned overlay (I am in the decorative concrete business). I applied a two-part polyurethane sealer to it. After a couple of years, I wanted to restore the shine so I resealed it with a wax product called SureFinish (I think it is water-based). Over the course of a few months, the floor looked more and more dull in spots, especially where walked on with wet shoes. I stripped the floor with a mild muriatic acid cleaner and applied an acrylic solvent-based sealer, thinking that I needed the solvent to restore the color. The floor looked great at first, but after about a month it began to dull again in spots. When I wash the floor it looks great, but the dull spots show up when it dries, and over time I’m getting more and more spots. Do you know why this is happening? Is it perhaps because the original sealer was a polyurethane that the others sealers are not bonding to, and with washing and water exposure, they are coming off? How do I now reseal over the original sealer? Answer: I think you are on the right track in terms of the other sealers not bonding to the original polyurethane sealer. Now you have multiple layers of different sealers, all of which seem to be wearing. Applying a water-based wax and then a solvent on top was also not a good idea. What is probably happening is diffusion. Where a sealer coat starts to come off, light no longer travels through it but instead diffuses, resulting in dull or white and hazy spots. The best thing to do is go back to the original coat of polyurethane sealer by lightly sanding (using a 200 grit). Then apply very light coats (800 to 1,000 square feet per gallon) of the wax. Test this remedy in a small area first to make sure it is working.

Removing bubbles and roller marks in a sealer

Question: I recently applied a two-component, high-solids aliphatic polyurethane sealer to a stained floor in a spa. First, I applied the primer coat with a roller and then applied the polyurethane, which has a longer pot life, with an airless sprayer. While applying the primer on the first half of the floor, I could see roller marks and bubbles and the primer started to string up on me. I mixed a new batch and proceeded to finish rolling the rest of the floor but at a much faster pace, and I seemed to have no problem. But now roller marks are visible throughout the entire floor, not to mention the bubbles. To remove the bubbles, I was told by the sealer manufacturer to go over the floor with a floor buffer or 150-grit sandpaper and then seal again. But will buffing be aggressive enough to take out the marks? Also, should I apply the primer using a sprayer instead of a roller, and should I mix smaller amounts of the sealer? I think I may have rolled on the primer too fast producing the roller marks. What do you recommend to fix the issue? Answer: Sanding will take surface bubbles out, but buffing with a floor machine will not be aggressive enough. If the bubbles go deeper than the surface, you may need to strip and start over. My suggestion is to try sanding out the marks and then reapply your topcoat. If this does not work, strip down to a point were no roller marks or bubbles appear and start over. Do a test area before doing the entire floor. I am not a fan of rolling in general, especially heavier bodied materials like epoxies or polyurethanes. All rollers produce lines, with more material coming off the ends of the roller as it moves across the surface. Depending on the material used, application temperature and pot life, the roller lines may or may not even out. The speed of rolling, the amount of material on the roller and the weight pushing down on the roller also play a role in leaving roller marks. Picture a car tire that has mud on it. If you drive slowly, the mud comes off the tire evenly. If you speed up, the mud flies all over and leaves more prominent marks on the outside edges of the tire. Heavy-bodied materials are always best applied in small batches and with a push-pull applicator such as a lamb’s wool or micro-fiber pad or a T-bar.

Blotchy spots in a glossy sealed floor

Question: I recently applied two coats of an acrylic sealer to a stained floor. After the sealer dried, the floor appeared blotchy, with some areas glossy and others not. What causes this, and should I apply more sealer to remedy the situation? Answer: If you were to look at a concrete floor under a microscope, you would see what looks like an endless range of plateaus and valleys. The number and depth of these plateaus and valleys is directly proportional to the finish of the concrete. A smooth finish has fewer of them while a rough finish looks like the Grand Canyon. When sealer is applied, it fills the valleys, but you may need to apply more than one coat depending on the finish of the floor. Typically when we see a floor that has blotchy areas of gloss, this means that some areas do not have sufficient sealer to fill the valleys. Applying additional light coats of sealer usually resolves this issue. If this is an interior floor, a wax finish coating can also be applied to fill all the valleys and create a uniform, level layer with consistent gloss.

Sealed surface is hazy white and blotchy

Question: On a project in Florida in mid-September, I applied a microtoppping on a Monday, acid stained the next day, and then neutralized and cleaned the stained surface the following morning. After letting the floor dry in 95 F heat for 2 ½ hours, I applied the sealer as directed. The sealer never became clear, and the entire sealed surface is hazy, white, and blotchy. What went wrong? Answer: This is a common problem, more often found with water-based sealers. There is always a trigger mechanism for sealers becoming cloudy or white, and we need to timeline your project to find what it is. You allowed approximately 24 hours of cure time for the overlay, which is standard and acceptable. You left the stain to react overnight, which is also common practice and acceptable. The problem lies in the short 2 ½ hours of dry time after you neutralized and cleaned the stained surface. Even with the high air temperature, the humidity was not taken into consideration. Most sealers need 12 to 24 hours of dry time before application, especially when a large amount of water is used in the cleaning process. So in this case, moisture was trapped under the sealer, causing the white, blotchy haze. Depending on the type of water-based sealer you used, a thin application of solvent might loosen the sealer enough to allow the moisture to escape. Otherwise, you will need to strip the sealer, clean the surface and allow it to fully dry, and then reseal. Four key factors to always be aware of when sealing are moisture, temperature, cleanliness, and application method. Also, read the label, because in this case it clearly stated minimum dry times of 12 to 24 hours before application. More information on sealing stained concrete is available in Bob Harris’ Guide to Stained Interior Concrete Floors, as well as from most reputable stain and sealer manufacturers.

Correcting uneven gloss on a sealed floor

Question: I applied two thin coats of a high-gloss sealer to a stained concrete floor, following the manufacturer’s instructions, but some areas of the floor look dull instead of shiny. What went wrong, and how do I fix the problem to achieve a uniform shine? Answer: It’s not uncommon for an uneven gloss to occur after two thin coats of sealer have been applied to a stained floor. The cause is different levels of porosity in the concrete surface. In some areas, the concrete is more porous and most or all of the sealer was absorbed into the substrate. These areas look dull because very little sealer remains on the surface to reflect light and produce gloss. In other areas, the sealer has saturated the surface of the concrete while leaving the desired film on the surface. This film is the protective barrier and reflects light to produce the level of gloss you want. To eliminate the dull spots and produce a nice, uniform gloss, apply an additional coat of sealer followed by two or three coats of a floor wax or finish. These finish coatings are low cost, go down very thinly and are easy to maintain. They can be applied with a micro-fiber mop, and they dry in a matter of minutes. See this video on using sacrificial waxes for concrete floors.

Sealers perform differently, why?

Question: On a recent stained concrete project, some areas of the floor were sealed with a two-part polyurethane sealer, while other areas of the same floor where sealed with a solvent-based acrylic sealer. Why did the two-part polyurethane peel off, while the one-part solvent-based acrylic is still down and performing great? The surface has a hard-troweled machine finish, and no additional surface prep was completed prior to staining or sealing. Answer: This is a case of chemical versus mechanical bonding and solids content. Two-part polyurethane sealers form only a mechanical bond with concrete. This is why profiling the surface – creating more surface roughness – is always called for when working with two-part polyurethane sealers. The same reason two-part polyurethane sealers don’t chemically bond to concrete is also what makes them such good sealers. They don’t chemically stick to anything, and nothing chemically sticks to them, including oil, gas, solvents, water, dirt, and graffiti. The other major factor is solids content. Most two-part polyurethane sealers are high in solids, above 55%. The higher solids content makes them less able to penetrate the concrete surface, thus requiring additional surface profiling to promote adhesion. Conversely, one-part acrylics bond both mechanically and chemically with concrete and are lower in solids – typically 20% to 30%. They tend to wet out faster, even on hard-troweled surfaces. As illustrated by the case in question, an acrylic sealer may chemically bond to a hard-troweled surface, but the surface won’t have sufficient profile, or roughness, to mechanically bond with a high-solids polyurethane sealer. Most manufacturers of high-solids sealers require a well-defined profile before application of their products. The use of a primer or diluting the first coat of sealer are also common methods for promoting sealer adhesion on denser surfaces. Before applying a high-solids sealer, be sure to consult with the manufacturer and perform an on-site adhesion test. Find out more about two-part and one-part sealer technology and application methods from Surtec Inc.

Preventing moisture problems in concrete sealers

Question: I am doing a stained concrete project using an acetone-based stain. I plan on sealing the stained concrete with a water-based urethane. This is a large 8,000-square-foot floor in the cafeteria of a local manufacturer, and it receives heavy traffic. I just completed a moisture test (using a calcium-chloride test). I did three tests, with results that ranged from 6.13 to 6.58 pounds. But I understand the recommendation is no more than 4 pounds. This floor is on grade, and the concrete is over two months old with a vapor barrier under the slab. The interior humidity has been high (around 70%) due, I think, to rainy weather and wet drywall mud. Here is my question: Because of the high moisture readings, should I do this job? Is 4 pounds a strict guide, or are there some tolerances? For example, is 6.58 pounds acceptable but something higher, like 12 pounds, too high? This is the first time I have done a test like this. Answer: According to the ASTM standard for conducting a calcium-chloride test (ASTM F 1869), a reading above 4 pounds—the amount of moisture flow in pounds per 1,000 square feet over a 24-hour period—is considered a no-go for sealing. This is especially true for nonbreathable coatings, like the polyurethane you plan to use. That being said, you have a slab that should eventually drop below 4 pounds because of the vapor barrier. You hit the nail on the head in regard to humidity. This is a very real environmental factor often missed when contractors prepare to seal, especially interior floors. Concrete is a sponge, and if conditions are right it will absorb and hold moisture, both in liquid and gas forms. The process of osmosis now comes into play—the movement of a liquid or gas from an area of high concentration to low concentration until balance is achieved. If the air above your floor has a high concentration of water vapor, or humidity, then the concrete will absorb moisture until it contains water equal to what is in the air. The practice of closing doors and windows to «dry-in» a room or building can actually trap moisture and create a steam room of sorts, making the problem worse or creating a problem where one didn’t exist. Drywall mud, paint and rainy or hot, humid weather can cause high moisture contents indoors, which will cause concrete to absorb moisture. This moisture will stay in the concrete until the moisture content of the air above the slab abates. Whether the humidity is manmade or natural, it can cause short-term high moisture readings, especially in the spring and fall, when days are warm and nights are cool. Wait for a dry spell, open as many windows and doors as possible, use a fan to move air across the floor, and take another test after 24 to 36 hours of drying. If the HVAC system in the building is operational, run the air conditioner to help remove moisture. When the moisture readings drop low enough for you to seal the concrete (at or below 4 pounds), apply the sealer in the afternoon or evening, when humidity is lowest.

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