Expert Tips: How Do You Protect Polished Concrete During Construction?

When stained, polished, or sealed concrete floors are installed in new residential buildings, they're typically among the first things to work on. Doing this early helps guarantee a good-looking, strong installation at a reasonable, affordable price.

However, this also exposes the finished floor to potential damage and contamination throughout the construction project. To ensure this, it's crucial to protect concrete floors once they're done correctly. So, how do you protect polished concrete during construction?

When Concrete is Newly Laid

Newly laid concrete is very vulnerable to many things. When it's curing, we recommend covering the concrete with a layer of plastic sheeting, which will keep the surface clean and prevent moisture from escaping too quickly.

Controlling the moisture and keeping the surface wet will promote a stronger, less porous slab, preventing the concrete finish from looking dry and dusty.

It's important to ensure the plastic sheeting is flat and smooth, as creases can cause curing lines in the slab's surface. Curing lines look like darker marks on the face of the concrete, which don't match the rest of the surface in coloring. They can't be removed by dry polishing or using abrasives.

After a 28-day curing period, the plastic sheeting can be removed and replaced with soft painters' dust sheets. The core sheets should then be placed back over the concrete to protect it until your polished concrete floor is created.

Concrete is Not Indestructible and Easily Stained

From our experience, concrete is often misunderstood as indestructible. Many clients believe it is unbreakable, won't chip or dent, and will often not even stain.

Unlike other flooring types, such as wooden floors, tiles, or linoleum, we can't argue that concrete is an incredibly strong medium.

What is widely misunderstood is that concrete is actually a very porous material. This is caused by the multitude of aeration holes within the slab, created by the random way that concrete is mixed and laid. When a surface is porous, it will instantly want to 'drink' any spill that lands on it.

Often, there isn't even time to mop the spill up; by the time you've fetched a cloth, the liquid has already been drawn into the concrete's mass.

Many people believe that staining is repairable through grinding, but sadly, this is often not the case; it all depends on how far into the slab any spills have been incorporated.

As we only grind a maximum of 3mm - 4mm from the surface and liquid that has seeped into the concrete mass further than that will remain, it's always preferable to prevent this from happening in the first place.

How to Prevent Concrete Stains

Many people mistakenly think that concrete can't be stained, but it's actually a very porous substance with lots of tiny holes in the slab. These holes are caused by the unpredictable way concrete gets mixed and poured. Because this surface has so many pores, it quickly soaks up anything that spills onto it. It happens so fast that you may not even have time to clean it up. By the time you get a rag, the liquid might have already been absorbed into the concrete.

While you're shielding your concrete during a construction project, remember that it might end up with marks or even change color in the following situations or ways:

• Blue or red chalk: Don't use blue or red chalk on your concrete floor since these colors cannot be erased and will still be visible under most stain shades. Instead, when you need to mark your concrete, go for orange chalk because it washes off entirely with plain water.
• Avoid taping the floor: Even if it seems safe, you should always avoid putting tape on your concrete floor to prevent damage. When the tape is pulled off, tiny particles will be taken from the surface of the concrete. When this area is stained later, the stain will appear darker here than in other areas of the floor.
• Leaving metal on the floor when it is wet: Don't leave screws, nails, or any other metal items on a wet concrete floor. If you do, the moisture will rust the nails, creating nail-shaped, reddish stains on the concrete. The same type of marks can happen if you leave wooden boards on the floor.
• High-viscosity oil leaks: High-viscosity oil is great for lubricating tiny and complex parts in machines, but when it touches porous concrete, it will soak into the holes in just a few minutes.

In other words, don't use anything on a hardwood floor that you wouldn't put on a concrete floor. There are methods to clean up marks on concrete, but the results will be challenging, so it's best to use them only partially.

How to Prevent Scratches and Chips in New Concrete

Fresh concrete is prone to chipping and scratching in various ways. To keep concrete safe from damage during construction, steer clear of these activities:

• Pouring acid: You should never pour acid on your concrete floor. When acid reacts with the lime in concrete, it neutralizes it, causing it to lose its stability.
• Cutting plywood: If you're cutting plywood or similar materials on 2-by-4s resting on the concrete, the blade might hit the concrete if the plywood bends. This can create unsightly marks, so it's best to avoid this.
• Screws in lift tires: The tires used on hydraulic lifts are constructed from soft rubber, and when they go over a nail or screw, the rubber will easily pick it up. As the lift continues to move, the nails or screws embedded in the tire can cause chips in the concrete floor. To reduce the chance of lifts running over metal objects, you can use tire bags, which can prevent about 80% of screws and nails from getting stuck. This is because the canvas material, unlike soft rubber, is not pliable. However, some screws will still get picked up by the tires, so you must still check them regularly.
• Drops: Even if workers are extremely cautious, some items like tools or building materials might fall and create cracks or holes in the concrete. Fortunately, if this occurs, you can find a specific product designed to patch up the holes, which helps them blend in so they are less noticeable. A wide range of these products come in many shades, letting you closely align the patch to the color of your concrete after it has been polished. These products also accept color well and maintain the polish for a long time.
• Entrance damages: A spot on the construction site where damage tends to occur quite often is near the entrances. When workers and heavy equipment come from outside, they usually track debris, which also wears down the concrete right at the entrance area of the site. Mud can get ground into the concrete and stain it. In colder climates, salt from sidewalks and roads is also brought in. To protect the concrete near the entrances, we recommend laying down mats specifically designed for this purpose. These mats often feature self-stick surfaces, so you can peel off the backing paper and then apply it to the surface.

Scheduling Matters

Polished concrete that's fully exposed requires two steps to complete. The initial step happens around ten days after the concrete is poured and has cured enough, involving a deep cut of about 5 to 8 millimeters to reveal the aggregate below the surface. Attempting to grind the floor when walls, pipework, cabinetry, etc, are already in place can be a pain, so this step must take place before construction begins to ensure that the aggregate exposure level is consistent and the slab is perfectly flat. 

Most commercial grinding machines can only grind within 30 millimeters of walls and won't fit into hard-to-reach areas like cupboards. Edges and areas with restricted access should be 'hand finished' using a hand-held grinder. Having no or limited exposure to polished concrete typically means there's just one step, and it usually happens near the final stages of building. The best time to achieve nil, random, or stage two of full exposure polishing is when cabinetry, doors, and baseboards haven't been installed yet.

How Do You Protect Polished Concrete During Construction??

Never cover a concrete slab that has yet to cure for at least 28 days fully. If you polish the floors before framing, wait until the house is completely dried before covering that floor. While framing and roofing, use a magnetic roller to pick up any nails or other metal objects on the polished slab surface. Rust can stain a decorative concrete slab.

Always cover the floor with a durable product to last through construction. Ram Board is the most common brand-name product, although many similar products are sold at specialty construction stores. Materials like painter's paper generally need more durability to last an entire home construction, especially in high-traffic areas.

Always tape the floor covering to itself and to the base plate, never to the floor itself. If tape is left on the floor for too long, it might leave behind sticky adhesive, which can be expensive to fix. This is a typical mistake when installing a floor.

Be extra careful when using purple PVC primer and pipe thread-cutting oil on the floor. If they spill, these liquids can seep under protective floor coverings and stain the concrete if not quickly cleaned.

Never put plastic over a polished concrete floor. Freshly poured concrete has a lot of moisture, and plastic can interfere with its curing. Because of this, you should also avoid using plywood and masonite.

At Which Stage During Construction Should Concrete Be Polished?

Since polishing concrete can eliminate spilled drywall mud and paint overspray from concrete slabs, many builders and contractors prefer polishing slabs towards the final stages of the construction process.

That said, this is usually not a good idea. Polished concrete floors are considerably more resistant to scratches, chips, and stains than bare concrete slabs. This is why it's a good idea to polish the concrete slab early in construction.

To know more about polished concrete and how to protect it during construction, please reach out to us today!