Guide to Concrete Resurfacing

Invented by the Greeks and perfected by the Romans thousands of years ago, concrete is the most popular and useful building material on the planet. Millions of cubic yards have been poured and our lives would be quite different without it. While hugely beneficial, concrete is not perfect and achieving success requires an understanding the material, its limitations, and thought into its design.

Concrete Overlays
Decorative concrete overlay is a thin material the consistency of a milkshake. It is designed to be applied at the thickness of a credit card. The material forms a nearly inseparable bond with the concrete and can be textured, patterned, stained or painted in many attractive ways. When applied on properly prepared concrete, the material has amazing bonding capability and will provide years of service.

Surface Preparation
Concrete overlay gives the surface its texture. The specifications for every overlay manufacturer state that the material must be applied to bare concrete that has a surface profile similar to that of 100 grit sandpaper. The industry has created the Concrete Surface Profile (CSP) scale to standardize the amount of profile required. The scale ranges from the lowest profile of CSP-1 (acid etched) to CSP-9 (extreme shotblast). A CSP-2 is commonly achieved by diamond grinding the surface. Best practice is to attach the grinders to industrial-sized HEPA vacuums to capture as much dust as possible; however, the process cannot be made completely dust-free.

Large floor grinders, diamond tooling, vacuums, and the truck or trailer to transport them are expensive pieces of equipment, which many smaller installers can’t afford. Surface preparation is also the most labor-intensive part of the installation. For these reasons, smaller installers like to skip or short-cut the surface preparation process. Some will claim that they can install a new surface over the top of the existing surface without any grinding, or they will fail to remove parts of the existing surface during the install. Either way, it is likely that the surface will fail sometime in the future.

When done properly, the material bonds strongly to the concrete. The bond is oftentimes stronger than the original concrete and you will receive many, many years of service.

In engineering terms, concrete is very strong in compression (forces that push material together) but relatively weak in tension (forces that pull material apart). In an attempt to minimize its weakness in tension, engineers add steel, fiber mesh or other type of reinforcing which is good at resisting being pulled apart. Since concrete is weak at resisting being pulled apart, it is prone to cracking. A common joke in the industry is that there are two types of concrete – concrete that has cracked and concrete that will crack.

Concrete cracks for a number of reasons including improper compaction of the base, a lack of saw cuts, erosion under the slab, a lack of reinforcing, thermal expansion and contraction, and heavy loads. Ideally, our industry would have a glue that would permanently adhere moving concrete slabs back together. Unfortunately, that material does not exist. Concrete slabs which want to move apart exert tons of force and will break any bond. Even if such a material existed, the concrete has demonstrated that it needs to move and it would then crack in a different, but nearby location.

However, if the concrete is done moving, there are a number of techniques for repairing cracks including V-shaped cuts and filling with epoxy or other material. These repairs may successfully mend the crack as long as the crack is not moving. It is impossible to tell if a crack is moving or not until after it is repaired. Since our industry can’t tell if a repair will hold or not, reputable resurfacing companies do not warrant crack repairs. If one does, beware.

We have found that the best approach on cracked decks and driveways is to incorporate the cracks into the design. Our Pacific Stone system uses the existing cracks and adds new artificial cracks to create an attractive flagstone appearance. Cracks become part of the design and any new cracking simply becomes part of the intended look. We avoid geometric patterns such as tiles, squares or rectangles because the human eye is immediately drawn to a crack which doesn’t conform to the surrounding pattern.

Drainage and Low Spots
The Tile Council of North America recommends ¼” per foot of slope to achieve proper drainage. Most lanais, driveways and pool decks in Florida do not have anywhere near that amount of slope. As a result, almost all of them have standing water. As long as the standing water evaporates in a relatively short time this is usually not a problem. It is generally impossible or uneconomical to try and obtain the proper slope on an existing deck. For example, a deck that extends 20’ away from a house would require 5” of sloping material be placed at the house. It is unlikely that there is 5” of vertical space below the door thresholds, and even if there was, it would be cost-prohibitive to re-slope the entire deck.

Since the deck was likely constructed without the proper slope, some ponding can be expected in the low spots. Resurfacing contractors can fill the low spots prior to the decorative topping if they are identified by the customer beforehand and incorporated into the contract. However, filling a low spot is not guaranteed to achieve the goal of draining the water off the deck because of the lack of slope. What may occur is that the water finds another low spot and goes there instead. This is called “puddle chasing” and a lot of time and expense can be expended without achieving a properly drained deck. Creative Resurfacing will fill low spots identified prior to resurfacing but we do not guaranty proper drainage.

Another drainage problem with Florida pool decks is a lack of drains, drains that are too small for the water flow, or have improperly designed discharges. Drainage systems are commonly undersized for the volume of water they encounter. In addition, the drain typically discharges into a wall of soil at the edge of the pool deck. Once the drain fills, the owner must wait until the soil absorbs the water for the drain to empty. During heavy rains, the surrounding soil is saturated so this could take a long time. In those circumstances, customers should consider installing a French drain system outside of the pool deck.

Surfaces are textured to provide visual interest and to aid in slip resistance. Slip resistant material can also be added to coatings. However, the greater the slip resistance the greater the difficulty in cleaning the surface, and vice-versa. Imagine rubbing a cotton ball across sand paper. We have selected our textures and coating to provide a good balance between slip resistance and cleanability.

Concrete is a porous material which absorbs and wicks moisture. Interior concrete usually has a moisture barrier under the slab; however, exterior concrete rarely does so the soil moisture must be allowed to escape through the slab and the coating. All decorative concrete needs to be painted or sealed to preserve the color and resist staining. These paints and sealers are designed to breathe, meaning that they let moisture vapor pass through. When there are too many layers of coatings accumulated over time the layers will no longer breathe. The moisture is trapped under the coating and pressure builds. This is called hydrostatic pressure. The pressure will eventually cause the coatings to come off. At that point, recoating over existing coatings will no longer work and all of the coatings must be removed before any new coating is added.

Flake Systems
Flake systems such as our Rapid Garage system are installed by throwing colored flakes into an epoxy, polyaspartic or polyurea coating and topped with a clear coat of the same. The system works great as an indoor flooring system. However, problems arise when a flake system is used outdoors. First, the system is a monolithic application with large homogenous areas between joints or saw cuts. On cracked concrete (see discussion above), the crack will stand out on the uniform background and the human eye will be immediately drawn to the crack. Second, the coating material is very sensitive to moisture. Indoor concrete has a moisture barrier under the slab which prevents ground moisture from moving up through the slab. However, exterior concrete does not. The coating materials will break down and turn black over time when exposed to moisture from above (like rain or pool water) or below. A vapor barrier coating can be applied first; however, vapor barriers must be applied to shot blasted (CSP-3 or higher) concrete to be effective (see Surface Preparation above) which significantly increases the cost of the system. For this reason, unscrupulous installers often skip the vapor barrier. Third, these materials are not breathable, which means that ground moisture cannot pass through the coating. Pressure builds underneath the coating (hydrostatic pressure) and will eventually delaminate the surface. Fourth, these coatings tend to break down or turn yellow under UV light, which is not what you want in the Florida sun. Lastly, repairs to flake systems can be unsightly. The flake tends to fade under UV light so any spot repairs using new flake will not match the faded rest of the deck. This system suffers very high warranty claims and is not recommended for outdoor use.

Above Grade Structures and Rusting Reinforcing
Engineers add steel and mesh reinforcing to concrete to compensate in an area where concrete is weak which is being pulled apart (tension). The weakness of steel rebar is that it is susceptible to rust. Rust is caused by chloride ions (salt) in water attacking the rebar. When steel rusts, it expands which breaks apart the surrounding concrete. The soundness of the structure could then be affected. Crumbling concrete is not a significant issue with on-grade concrete because the concrete can be easily removed and replaced. However, when that concrete is an above-grade supported structure, such as a condominium balcony or walkway, it is a significantly larger problem.

One way that engineers and architects seek to delay this attack is by waterproofing the concrete surface. When resurfacing a supported concrete structure, the owner should consult a qualified professional such as an architect or engineer as to whether the surface should be waterproofed as part of the resurfacing.

Licensing, Reputation and Integrity
Licensing – While the State of Florida does not require a license to resurface concrete, some counties and cities do require such a license. This license is usually a flatwork license or a general contractor’s license. Many companies will try and pass off a general business filing as satisfying the requirement; however, it does not.

Insurance – Make sure you request a certificate of insurance from every installer showing both general liability and worker’s compensation insurance. Many small companies will provide an “Owners Exemption” from the state of Florida. However, this exemption is only good for the owner, not anybody else helping the owner. Using an installer who doesn’t have worker’s compensation insurance could lead to the customer becoming liable for lawsuits and damages.

Company History – Many decorative concrete installers will try and pass off their manufacturer’s long history as their own. Manufacturers generally don’t install their materials, they simply sell them to others to install. Your contract will be with the installer, not the manufacturer, so understand who it is you are dealing with. Owners can check the installer’s status and time in business at www.sunbiz.org.

Manufacturer Distributorships – Disreputable manufacturers will solicit unsuspecting entrepreneurs, sell a few zip codes as an exclusive territory, train their installers for a few days, and sell them a large initial material order. These new business owners are woefully undertrained, can’t make a living in the small territory, and greatly overpaid for both the territory and the materials. They go out of business in a short time and the manufacturer repeats the process.

Warranties – Manufacturer’s will only warrant the cost of the materials, which is only a small percentage of the job. The vast majority of the cost of a resurfacing job is labor. That portion of the warranty is being provided by the installer. Long-duration warranties are only as good as the company behind it, which unfortunately is not always very long.

Lead-Gen Companies – Some decorative concrete companies aren’t really decorative concrete installers at all. They are lead-generation companies who collect leads and sell them to real installation companies. They have great looking websites but no installers.

Credentials – Creative Resurfacing is the largest concrete resurfacing company in Florida with locations throughout the state. We have been in business for 14 years, have A+ BBB rating, and are a licensed and bonded Florida general contractor. We maintain full general liability and worker’s compensation insurance. We have worked for the largest hotel chains and general contractors in the country, and have appeared on the long-running television show “This Old House”. Sherwin Williams is our primary material supplier. They are a publicly traded Fortune 500 company with over 1,500 locations.

Conclusion
Concrete resurfacing projects done right will result in a beautiful job that will stand the test of time. If you have any questions, please call us at (727) 230-8885.