When it comes to hardscaping your outdoor space, sometimes you don't have the time or money to invest in ripping out all of your existing concrete to put in new pavers or stone. A good concrete overlay will solve this problem by upgrading your existing concrete surface without enduring the headache or price tag of a full renovation.
Concrete overlays have been gaining popularity indoors for a while as a way of both creating and resurfacing concrete floors, or upgrading existing concrete floors. But the concrete overlay has also become popular in outdoor spaces as well. Now, concrete overlays are being added not only to features such as concrete driveways, but pool decks and other projects as well.
What is a concrete overlay, anyways?
If this is the first you're hearing about concrete overlay as a practice, you probably aren't exactly sure what we are talking about. Luckily, it's a pretty straightforward concept.
A concrete overlay is both a feature and a practice used to treat existing concrete surfaces. In short, concrete overlays are layers of material that are added to areas such as concrete floors, a concrete driveway, or other areas where hardscaping is desired and the existing surface is in need of renovation or repair.
When finished, they create a smooth concrete surface that is functional and aesthetically appealing. This concrete overlay can be left smooth, but can also be stamped or finished with a decorative effects. But don't be confused, concrete overlays are not the same as pouring new concrete. There are several ways a concrete overlay differs from the existing slab of concrete that may make up your back patio.
What is concrete overlay material made of?
Overlay materials are made from a mix of concrete cement and other items such as polymer resins and pigmentation. This mixture varies slightly in make up from the material that comprises a traditional slab or concrete floor. The composition of the concrete also depends on the application of the product or the intended finish.
One popular approach is to purchase your overlay blend in a preblended bag. Concrete overlay bag mixes are popular for their ease of use. Just add water and you're in business. Other options are a bit more involved.
In that case, the user must mix a polymer additive and the final pigmentation or color desired with the cement blend to get the final mix. Sometimes, the mix can be placed directly over a properly prepared surface. More on that later. Other times, you may need to apply a primer or bonding agent.
In general, if you are looking into a DIY overlay and you think your existing surface is prepped correctly, investing an a just-add-water mix that is pourable is the quickest and easiest option on the market.
Concrete overlays can vary widely not only in make up, but also in thickness and design. A reparative concrete overlay job done to a driveway is likely to be thicker than a purely decorative concrete overlay done to a pool deck or patio. In general, a concrete overlay ranges anywhere from an 1/8 of an inch to a full inch in thickness. The option that is best for your space will depend on the desired finish of your project, as well as the state of your existing concrete floor, driveway, or pool deck.
How to choose your overlay.
As we mentioned, there are a few things that determine what the best overlay option will be for your space. So before you commit to this new DIY project, take the time to analyze your space. First of all, are you doing a minor, decorative facelift, or are you trying to conceal and repair significant damage?
If the answer is a very minor facelift, then you should look into a decorative concrete overlay. These overlays are typically thinner, and don't add an enormous amount of structural integrity to surfaces. We'll elaborate more on the options available for a decorative overlay in a moment.
If you are looking to do more significant reparative work to damaged concrete surfaces, then you will need to look into a more heavy duty, significantly thicker, overlay. Now, this isn't to say that you cannot attain a decorative finish with a repair-centric overlay project. But the base must be thicker, and the material must work to conceal the existing damage before adding additional aesthetic value to the space.
A Word of Caution
Your concrete overlay, decorative or not, is only as good as the existing concrete that is beneath is. While you can use this method to repair, or resurface chipped and cracking concrete floors, pool decks, etc, there are limits to its power.
If you're dealing with concrete that is severely damaged or spalling, heaving from salts and seasonal freezing and thawing, or is significantly cracked and uneven due to unstable soil, take a pause. Is it really worth it to put a band aid on a problem that requires reconstructive surgery?
A thin concrete overlay can hide many stains, cracks, and imperfects. A thick concrete overlay can correct moderate cracking and unevenness. But even the best new concrete overlay will crack or look unfinished if the base is structurally unsound.
In this case, it's better to start from scratch. Yes, it is more expensive to rip up your entire patio or existing floor. But why pay for a corrective process that will not address a major underlying problem?
Decorative Concrete Overlays
As we briefly touched on earlier, one of the easiest ways to breath new life into a concrete floor or hardscape is to add a decorative overlay. Concrete has been taking on new forms in the outdoor design world for decades. From concrete pavers to stained and stamped concrete, the material is more versatile than a lot of people may realize.
There are a lot of different ways to put your own spin on this technique. It's probably more reliable to hire a professional to complete decorative overlays, but many a homeowner has tried and triumphed with a DIY approach.
Stamped Overlays
One of the best ways to add texture, visual interest, and a modern feel to basic concrete is to use a stamped concrete overlay. A stamped concrete overlay is exactly what it sounds like. In this process, concrete is poured to around 3/4 inches thick. Once poured, there are a few common tools used to create the finished stamped concrete effect.
The tool you choose to complete your project will depend on your desired finish, and the conditions of the project. While flat driveways or horizontal concrete slabs may benefit from one type of stamping tool, vertical surfaces may demand a different approach. All stamping should be done when the overlay material is dry, or almost dry.
Stamping Mats
A stamping mat is used to imprint a pattern of your choice into the concrete. They range from rigid to floppy, depending on the strength of the polyurethane. Rigid stamping mats are most common, and are firm enough to support human weight. These mats usually create the deepest impression on stamped concrete and leave a prominent impression, making them great for creating prominent patterns.
Semirigid and floppy stamping mats are not built to support the weight of a person standing on top of them. Therefore, the pressure they apply is lesser, and the stamped concrete overlay that they leave behind is less significant. There are areas, however, where these tools are incredibly useful.
If you are creating a stamped concrete overlay on a slope or flaring surface, such as the end of a driveway, then the flexibility in a semi rigid or floppy mat is necessary.
Texturing Skins
The second tool used to imprint a pattern on a decorative concrete overlay is call a texturing skin. While we are slotting this under the stamped concrete section, this may not be what you think of when you envision stamped concrete.
As the name suggest, texturing skins or texture mats are used to create a uniform texture in your concrete overlay. However, unlike a stamping mat, they do not leave any prominent grout lines. Instead, the embed a uniform texture in a thin layer across the surface of the decorative concrete.
The end product is a seamless texture with no beginning and end point. It looks as though the concrete was simply poured this way. This is a great technique for a more subtle finish to stamped concrete overlays.
Colored or Stained Concrete
Stamped concrete is used to create or mimic textures. Stained concrete is used to bring color, depth, and pattern. You could create an incredibly precise stamped concrete overlay, but without proper coloring, it will still just look like basic, gray concrete.
For example, say you are creating a concrete overlay on the walk out patio behind your home. You are envisioning a mock-flagstone finish. Work begins, and your concrete slab is covered by a new, stamped decorative concrete overlay. Your contractors take their time with surface preparation. The grout lines are perfect. Your old concrete is hidden perfectly. But something is still missing. Color!
In the broad scheme of backyard renovation, colored concrete gives you some of the best bang for your buck. The impact a great staining job can have the rest of your space is significant.
How It's Done
Staining your decorative concrete can be done in several ways. The first is to incorporate the color into the mix of the concrete itself. This will result in a an easy and continuous finish. At the end of the project, your pool deck or driveway will simply need to be sealed to prevent damage from foot traffic or other environmental disruptions such as moisture intrusion.
In some cases, your concrete may be laid first, and color may be added in a thin layer to a finished concrete floor, concrete wall, or other surface. This process involves applying a thinner layer of polymer, or using a more formal chemical or acid based stain.
Acid Stains
Acid stains require your decorative concrete to be in good condition and prepared properly. Even then, it may be hard to predict how the acid will react with the concrete substrate on your property. If your concrete is cracked, pitted, or has significant inconsistencies, then an acid stain will react differently over the surface. This can result in a flawed final effect.
This is why, though DIY approaches to concrete projects are tempting, it is often best to leave the work to seasoned professionals.
Water Based Stains
Water based stains are more forgiving and easier to work with. To use, apply to the entire surface. This type of stain works on less even or more imperfect surfaces because they do not interact chemically with the substrate of your project. This makes water based staining more predictable, and allows the color of the stain to be easily adjusted and customized for your specific project.
Preparing Existing Concrete Surfaces
Before you or your contractor dives headfirst into the resurfacing process, there are multiple things that need to be done in advance of the actual application of the overlay. In the case of overlay application, no preparation steps should be skipped or skimmed over. Doing so can make the finished result disastrous.
Determine Stability
Before you ever commit to an overlay, determine whether or not the existing concrete is even suitable for the project. Heavily damaged, cracked, or spalled concrete should not be considered a good candidate for resurfacing.
Clean and Repair
If your concrete is stable, then the next step to clean it and repair any problem areas. To clean, use a high velocity pressure washer to give the entire surface a good cleaning. Pressure washing is a fast and easy way to kick up any stuck dirt or grime.
Prime
Once clean, repair any major problem areas and ensure that your surface is stable. Then, you can move onto priming the concrete. Once the area has been checked, undergone a good pressure wash, and is primed, application of the decorative overlay should be done within the next 90 minutes. Otherwise, another cleaning may be necessary.
Can You DIY a Decorative Concrete Overlay?
You may have read through this entire article and thought to yourself, "This all seems pretty straightforward! I can definitely do this myself." This train of thought, though understandable, is deceptive. Even after a thorough general explanation, we have barely cracked the surface of the world of concrete overlays.
While you may be able to execute some aspects of the project yourself, there are some things that will take you by surprise as a DIYer. Overlay concrete behaves differently than regular concrete. The preparation process is different, the mixes are different, and the steps needed to finish an overlay are different than the process of pouring say, a regular slab driveway.
Ask an Expert
For all these reasons, we encourage our readers to reach out to their local concrete contractors. Nobody will give you the results you are looking for better than a professional. And while doing an overlay isn't necessarily cheap, it also shouldn't break the bank the way a pool installation or custom structure will. Concrete is a cheap material. What you are really paying for is expert craftsmanship, and the knowledge that your final result will be beautiful and durable.
If you do choose to ignore our advice and DIY, make sure you know what you are getting into. Familiarize yourself with common issues in the process so you can navigate them should they arise. Know the surface you are working with well, and have a specific end goal in mind. And if all goes wrong, you can also call an expert to fix your mistakes.