Skim-Coating Concrete Curbs: A Step-By-Step Guide

Skim-coating a concrete curb is a great way to give it a new lease of life. Whether you're looking for an aesthetic change or just want to cover up cracks and imperfections, skim coating is a simple yet effective solution. It involves applying a thin layer of cement-based material over the existing surface, drying, and hardening into an even coat that covers any imperfections. This process not only renews the appearance of concrete curbs but also extends their lifespan by improving drainage and waterproofing.

Prepare the surface

Before you begin skim coating a concrete curb, it is important to properly prepare the surface. Start by laying plastic drop cloths on the floor and covering any furniture or items that will remain in the area during the skim coating process.

Next, remove any chipping or peeling paint on the surface using a putty knife or wire brush. If there is loose paint, apply a chemical paint stripper designed for the type of paint on your concrete (water-based or oil-based). When in doubt, choose an oil-based remover. Allow the product to work as instructed, then scrub or wash away the stripper and paint. If removing paint applied before 1978, assume it contains hazardous lead dust and hire professionals for removal.

Thoroughly clean the concrete surface with a pressure washer to remove any dirt, debris, grease, or dust. If possible, pressure wash with detergent for a really clean slab.

Fix any drainage issues before skim coating. If there are sunken areas, choose a concrete mix that can be troweled to a feathered edge. Mix it with water according to the manufacturer's instructions, spread it over the sunken area, and run a straightedge over it to level it with the surrounding area.

Repair cracks in the concrete surface using different products depending on the width of the cracks. For cracks up to 1/8 inch wide, use concrete dressing, and force the mix into the crack with a putty knife. For cracks up to 1/2 inch wide, use concrete-repair caulk and smooth the surface with a putty knife. Allow the repairs to cure fully before proceeding.

Once you have a level and clean surface, mask off any areas you want to keep clean, including expansion joints, with duct tape. Then, apply a concrete primer to improve adhesion and resist mould and mildew growth.

Mix the skim-coat

Skim-coating a concrete curb is a great way to repair and renew the surface. It is a simple and effective solution to cover up cracks and imperfections, giving your curb an updated look. The process involves applying a thin layer of cement-based material, which will then dry and harden into an even coat, covering any imperfections.

To mix the skim-coat, you will need a few basic supplies and tools. Here is a list of what you will need:

• Cement: This is the main ingredient of your skim-coat mix.
• Water: Water will be used to mix with the cement and create a workable texture.
• Bucket: You will need a bucket to mix the cement and water together.
• Electric drill with a stirring bit: This will be used to mix the cement and water together until a smooth, thick consistency is achieved.
• Trowel: A trowel will be used to apply the skim-coat to the surface of the curb.
• Putty knife: A putty knife can be useful for filling any cracks or holes in the concrete before applying the skim coat.
• Sandpaper or steel wool: This will be used to smooth down the skim-coated surface after it has dried.
• Primer and paint: Primer will prepare the surface for painting, and paint will give it the desired finish.

Now, let's get into the step-by-step process of mixing the skim-coat:

• Prepare your cement mix by combining cement and hydrated lime in a ratio of 3:1 or 4:1. You can also use a self-levelling cement mix, which will help you achieve a smooth, level surface more easily.
• Add water to the mix: Start by adding about one gallon of water for every 50-pound bag of cement. The mixture should be workable but not overly wet. Adjust the amount of water as needed to achieve the desired consistency.
• Mix the cement and water: Using your electric drill with a stirring bit, mix the cement and water together until you achieve a smooth, thick wallpaper paste-like consistency. Make sure to mix thoroughly to avoid lumps.
• Test the consistency: Dip your trowel into the bucket of mixed cement and fill it halfway. The mixture should be thick enough to spread onto the wall but not so thin that it drips off the trowel.
• Adjust as needed: If the mixture is too thin and runny, add a small amount of cement or hydrated lime to thicken it. If it is too thick and difficult to spread, add a very small amount of water and mix again.

Remember, it is important to wear proper safety gear such as gloves and eye protection when working with these materials. Also, make sure to practice your skim-coating technique on a small area or a scrap piece of material before starting on the actual curb to ensure you have the right consistency and technique.

Apply the skim-coat

Skim-coating is the process of applying a thin layer of material, such as cement, over a wall or curb to even out the surface. This process is a good way to prepare a cracked and uneven concrete curb for painting or other finishing. The procedure is straightforward and easy to follow.

Before you start skim-coating, ensure that the curb is clean and dry. Remove any loose debris from the surface with a vacuum cleaner or broom and wipe down with a damp cloth if necessary. Fill any cracks with appropriate filler material and sand down rough patches until they are completely smooth. You can also use a wire brush to scrub the curb and remove any stubborn dirt or debris.

Once the curb is prepared, you can begin the skim-coating process. Start by mixing your chosen skim-coat product according to the manufacturer's instructions. For a concrete curb, you will typically need a concrete mix with a slightly thinner consistency than usual. Combine the concrete mix with the recommended amount of water using a drill and paddle extension.

For a vertical surface like a curb, apply the skim-coat mix with a hand trowel, maintaining an even depth as you work your way across the surface. Recommended depths vary by product but normally range from 1/2 inch to 2 inches.

Start at one end of the curb and work your way across the surface. Dip the cement trowel into the bucket of mixed concrete and fill the trowel halfway. Spread the concrete onto the curb, using the flat side of the trowel to smooth it. Remove any excess concrete using the edge of the trowel in a scraping motion. Apply a thick enough coat to cover the surface with an even layer.

Allow the skim-coat to dry for several hours or as recommended by the manufacturer before adding additional layers if necessary. The desired thickness for each layer is typically around 1/8 inch. After the final layer has dried, use sandpaper or steel wool to lightly sand down the entire area until smooth.

After sanding, you can prime and paint the curb to finish it. When applying multiple layers of concrete mix, allow ample drying time between each application. This can vary depending on the temperature, but typically 24 hours should be sufficient.

Lastly, always ensure your workspace is properly ventilated while using these products due to their strong odours, which can cause irritation when inhaled.

Allow to dry

Allowing your skim coat to dry is a crucial step in the concrete curb repair process. The drying time will vary depending on the product used, the thickness of the coat, and the ambient air temperature. It is important to refer to the manufacturer's instructions for specific drying times.

For the base coat, a general rule of thumb is to allow it to set for 4–6 hours before proceeding to the next step. During this time, the base coat will begin to harden and develop its strength. It is important to let it set sufficiently to support the weight of the topcoat and any foot traffic that may occur during the application process.

For the topcoat, you can expect a longer drying time. Typically, you should be able to walk on the surface without causing damage within 24 hours. However, the full curing process can take up to 72 hours. This extended curing time ensures that the concrete achieves its maximum strength and durability.

During the drying process, it is important to protect the surface from rain or moisture for at least the first six hours. This will prevent any water damage or dilution of the concrete, ensuring that it sets properly. If possible, cover the area or protect it from the elements to ensure optimal drying conditions.

After the initial drying period, the concrete will continue to cure and harden over the next few days. It is important to avoid any heavy traffic or weight on the surface during this time. While it may feel dry to the touch, the concrete is still in the process of reaching its full strength.

Seal the surface

Once you have skim-coated the concrete curb, it is important to seal the surface to protect it from damage and give it a finished look. Here are some detailed steps to guide you through the process of sealing your skim-coated concrete curb:

Prepare the Surface:

Before sealing, make sure that your skim-coated concrete curb is thoroughly cleaned and dried. Use a mild detergent or degreaser with warm water and a soft brush or mop to remove any dirt or debris that may have accumulated during the skim-coating process. Ensure that the surface is completely dry before moving on to the next step.

Choose the Right Sealant:

Select a high-quality sealant that is suitable for concrete surfaces. Look for a sealant that will protect against staining, fading, and other damage caused by moisture and weather exposure. You can choose between an acrylic sealer or a masonry stain, both of which will improve the durability of the surface.

Apply the Sealant:

Follow the instructions on your chosen sealant for proper application. Typically, you will use a roller, brush, or sprayer to apply the sealant evenly across the surface of the concrete curb. Ensure that you cover the entire surface, including any edges or corners, for a consistent finish.

Allow Drying Time:

Sealants will require adequate drying time, so make sure to follow the manufacturer's instructions. The curing time may vary depending on the type of sealant used and the environmental conditions. As a general guideline, you can expect to wait at least 24 hours before walking on the surface and up to 72 hours for full curing before exposing it to heavy traffic or finishing with other materials.

Maintain Your Concrete Curb:

Regular maintenance is key to keeping your concrete curb looking its best. Sweep away any dirt or debris regularly to prevent buildup and discoloration. Reapply a coat of sealant every few years to maintain its protective qualities and enhance its resistance to wear and tear from foot traffic and environmental factors such as rain, snow, and ice.

By following these steps and properly sealing your skim-coated concrete curb, you will not only improve its appearance but also extend its lifespan by protecting it from the elements and everyday use.

Frequently asked questions