Concrete Skim Coats: Why They Crack And How To Prevent It (2024)

Concrete is a durable material that can last for many years, but it is not immune to damage. Over time, concrete can crack and chip due to various factors, such as weather conditions, an unstable foundation, or poor-quality concrete. When concrete repairs are needed, one option is to apply a skim coat, which involves spreading a thin layer of cement mixture over the existing concrete surface. While skim coating can improve the appearance of concrete and hide imperfections, it is important to note that it may not be a permanent solution for all types of damage.

Concrete skim coating is a cheap and simple way to resurface concrete floors

Concrete Skim Coating: An Affordable and Hassle-Free Way to Revamp Your Floors

If you're looking for a cost-effective and straightforward way to give your concrete floors a new lease of life, concrete skim coating is an excellent option. This method involves applying a thin layer of cement mixture to your existing concrete floor, providing a fresh and durable surface. Not only does it hide imperfections, but it also improves drainage and water resistance.

Benefits of Concrete Skim Coating:

• Affordability: Skim coating is a budget-friendly option compared to other decorative concrete finishes like stamping or exposing aggregate. The materials and tools required are relatively inexpensive, and you can even tackle the project yourself with the help of online resources, saving on labor costs.
• Simplicity and Speed: This process is suitable for both beginners and experienced DIY enthusiasts. It can usually be completed within a day, depending on the size of the floor. The basic steps include preparing the concrete surface, applying the skim coat in two layers, and then sealing the floor.
• Minimal Disturbance: Unlike other flooring renovations that may require removing the existing floor, skim coating only adds a thin layer, typically about 1/4-inch thick. This means it won't affect the alignment of your floor with adjacent surfaces like garage entrances or walkways.
• Aesthetic and Customization: Skim coating gives your floor a smooth, renewed finish. You can also add color to the mixture to personalize your space. For a more textured look, use a push broom while the mixture is still wet.
• Durability and Longevity: By skim coating your concrete floors, you can extend their lifespan by 8 to 15 years. The coating hides imperfections like cracks and stains, and it also improves the floor's ability to withstand heavy foot and vehicle traffic.

A Step-by-Step Guide to Concrete Skim Coating:

• Prepare the Concrete Surface: Wear protective gear and cover any furniture or nearby items. Remove dirt, debris, and old paint or sealants using a putty knife, wire brush, or chemical strippers. Clean the surface with a pressure washer. Fill any cracks or depressed areas with a patching compound, and sand or grind down any raised areas to ensure a level surface.
• Apply the Skim Coat: Mix the skim coat with water according to the manufacturer's instructions until you achieve a spreadable paste. Apply the first layer of the coat using a trowel or long-handled squeegee in a back-and-forth motion. Allow several hours or a day for it to dry.
• Apply the Second Coat: Mix another batch of the skim coat, which is usually slightly thicker. Add a base color if specified by the manufacturer. Wet the concrete surface and apply the second coat with a trowel, scraping off any excess.
• Add Texture (Optional): Use a push broom to create a textured finish while the mixture is still wet, preventing the floor from becoming too slippery.
• Seal the Floor: Apply a penetrating concrete sealer to protect the surface, enhance its stain resistance, and ensure its longevity.

With its affordability, simplicity, and durability, concrete skim coating is an ideal solution for revitalizing your concrete floors without breaking the bank or causing major disruptions to your space.

Before skim coating, repair cracks and damage in the concrete

Before skim coating, it is important to repair any cracks and damage in the concrete to ensure a smooth and durable finish. Here are some detailed steps to guide you through the process:

Prepare the Concrete Surface:

Start by wearing protective gear, including coveralls, gloves, and a mask. If working indoors, cover the floor and furniture with drop cloths to protect them from any dust or debris. Remove all items from the area you will be skim coating and protect any outdoor plants or décor by covering them.

Remove Paint, Sealants, and Debris:

Use a putty knife or drywall knife to scrape away any loose paint, sealants, or other materials stuck to the concrete surface. For paint removal, apply a chemical paint stripper designed for the specific type of paint on your concrete (oil-based or water-based). If you are unsure, choose an oil-based remover. Use a wire brush or paint scraper to scrub away any remaining paint after the stripper has been applied. For concrete surfaces with paint applied before 1978, it is recommended to consult professionals as the paint may contain hazardous lead dust.

Clean the Concrete:

Once you have removed all the paint, sealants, and other materials, thoroughly clean the concrete surface using a pressure washer. This will help remove any remaining dirt or debris and ensure the concrete is ready for the next steps.

Repair Cracks and Damage:

Fill in any cracks or damage in the concrete using suitable products. For cracks up to 1/8 inch wide, use concrete dressing, forcing it into the crack with a putty knife and trowel to create a level surface. For larger cracks, up to 1/2 inch wide, apply concrete-repair caulk using a caulk gun and smooth it out with a putty knife. Ensure that all repaired areas are completely cured before proceeding to the next step.

Level the Surface:

If there are any raised areas on the concrete, you may need to sand or grind them down to make them level with the rest of the surface. This step is crucial to ensure a smooth and even skim coat application.

Apply a Primer:

It is recommended to apply a primer to the prepared concrete surface. Primers improve adhesion, ensuring that the skim coat sticks well to the existing concrete. They also help prevent mold, mildew, and future cracking or peeling issues.

By following these steps, you can effectively repair cracks and damage in the concrete before skim coating, resulting in a smoother and more durable finish.

Applying a penetrating concrete sealer will keep the surface clean and resistant to stains

Applying a Penetrating Concrete Sealer

Skim coating is a great way to repair concrete surfaces and improve their appearance. However, to ensure the surface stays clean and resistant to stains, it is important to apply a penetrating concrete sealer. This is especially important if the concrete is exposed to the elements or heavy foot traffic.

Penetrating concrete sealers are products that absorb into the pores of the concrete and create an invisible barrier that protects the surface from water, dirt, stains, and other contaminants. This barrier forces liquids to bead up on the surface, making them easier to clean and preventing stains. Additionally, penetrating sealers can protect concrete from UV damage, oils, mould growth, and freeze-thaw cycle damage.

There are several types of penetrating concrete sealers available, including siliconate, silane, siloxane, and silicate-based sealers. Each type has its own advantages and is suited for different applications. For example, siliconate-based sealers are waterproof and can be used on a variety of concrete surfaces, while silane-based sealers are also waterproof but require multiple applications.

When choosing a penetrating concrete sealer, it is important to consider the specific needs of your project. If you are primarily concerned with protecting against water damage, a siliconate or silane-based sealer may be the best option. However, if you need protection against oil-based stains, a fluoropolymer-based sealer may be more suitable.

By applying a penetrating concrete sealer, you can help maintain the appearance and performance of your concrete while also protecting it from various types of damage. This will extend the lifespan of your concrete surfaces and save you money in the long run.

The concrete surface should be cleaned and any debris removed before skim coating

Skim coating is a process that involves applying a thin layer of cement mixture over a concrete surface to hide imperfections such as cracks, stains, or grout lines. It is important to prepare the concrete surface before applying the skim coat. This includes cleaning the surface and removing any debris or dirt.

Before applying the skim coat, it is crucial to ensure that the concrete surface is clean and free of any debris or dirt. This step is important because it helps to create a strong bond between the new and old concrete. Over time, concrete surfaces can accumulate dirt, dust, and debris, which can weaken the adhesion of the skim coat. Therefore, it is essential to thoroughly clean the surface before applying the skim coat.

One way to clean the concrete surface is by using a pressure washer or power washer. This will help remove any stubborn dirt, debris, or stains that may be present on the surface. For paint removal, a chemical paint stripper can be used, followed by scrubbing with a wire brush or paint scraper. It is important to note that if the concrete was painted before 1978, it is recommended to seek professional help as the paint may contain hazardous lead dust.

After washing the surface, it is important to fill in any cracks or holes using an appropriate filler or patching compound. This step ensures that the concrete surface is smooth and level before applying the skim coat. Once the filler has cured, the surface can be sanded or ground to create a rough texture, which will improve the adhesion of the skim coat.

Additionally, it is recommended to apply a primer to the concrete surface before skim coating. Primers improve adhesion, ensuring that the skim coat adheres well to the existing concrete. They also help prevent mould, mildew, and future cracking or peeling issues.

By properly cleaning and preparing the concrete surface, you can ensure that the skim coat will adhere correctly and create a strong, durable finish. This process will help extend the lifespan of the concrete and improve its overall appearance.

The concrete skim coat should be applied in two layers, with the second layer slightly thicker than the first

Skim coating is a process that involves applying a thin layer of cement mixture over a concrete surface to repair and improve its appearance. It is a great way to cover up cracks, stains, and other imperfections. When applying a skim coat, it is important to follow certain steps to ensure a successful outcome.

Firstly, the concrete surface must be properly prepared. This includes wearing protective clothing, covering or moving any items or plants in the surrounding area, and removing any dirt, debris, or old paint from the surface. Once the surface is clean, use a patching compound to fill in any cracks or depressed areas, and sand or grind down any raised areas to create a smooth and level surface.

The next step is to apply a primer, which will improve adhesion and help prevent mould, mildew, and future cracking or peeling issues. After the primer has been applied, you can move on to the skim coating process itself.

For the second layer, mix another batch of the skim coat, making it slightly thicker than the first. Depending on the manufacturer's instructions, you may need to add the base colour at this stage. Wet the concrete surface again, then apply the second coat using a trowel, scraping off any excess mixture with the edge. If desired, use a push broom to add texture to the wet mixture and prevent slipperiness.

After the skim coat has been applied, it is important to seal the concrete surface to ensure it stays clean and resistant to stains. A penetrating concrete sealer should be applied annually, especially for concrete surfaces exposed to the elements or heavy traffic.

Frequently asked questions