Leveling a concrete floor under laminate – different methods, same result

A level surface is essential for a seamless and long-lasting laminate installation. There’s a chance that a concrete floor isn’t always level, which could make installation difficult. Fortunately, leveling the concrete beneath laminate flooring can be accomplished in a few different ways, providing a stable and even base.

A typical technique is to use self-leveling compound. This is a well-liked product for leveling uneven concrete flooring. When self-leveling compound dries, it fills in low areas and spreads easily across the floor to create a level surface. Prior to application, the concrete must be carefully cleaned and any significant gaps or cracks must be filled. The compound is applied, settles in, and dries rather quickly, making laminate installation possible.

Another strategy is to grind down any elevated areas of the concrete floor. When there are isolated regions that are marginally elevated above the intended level, this approach works well. These high spots can be leveled off to match the rest of the floor by using a concrete grinder. It’s important to grind carefully to prevent overdoing it and developing low spots. To achieve a uniform surface, it is imperative to wear protective gear and work methodically across the floor.

A plywood subfloor is a workable solution if the concrete floor has large height variations. After the concrete has been partially cleaned and leveled, plywood sheets are placed on top of it. By making up for any small rises or dips in the concrete, the plywood creates a level foundation for the laminate flooring above. Since this method raises the floor slightly, door clearances must be adjusted appropriately.

The end result is always the same, regardless of the technique used: a level surface that firmly supports the laminate flooring. Depending on the installation’s particular requirements and the state of the concrete, each strategy has benefits. Through methodical method selection and proper preparation of the concrete, homeowners can guarantee that their laminate flooring not only looks fantastic but also holds up well over time.

Laminate flooring in your home

Let’s examine laminate flooring in more detail so that you can see how crucial a flat base is. How would you describe him?

• So, the laminate surface is assembled from individual boards, panels, which are more correctly called lamellas.
• On average, the thickness of such a panel is 1.2 centimeters, while the width and length are 20 and 120 centimeters, respectively.

That’s interesting to know! The most popular sizes are, of course, named. Although models with different parameters are also available, the essence remains largely unchanged.

• If you have already purchased laminate (you can do this in the store), take it in your hands and try to bend it slightly. You will see that the body of the lamella lends itself well and bends quite strongly, which indicates that it is impossible for it to withstand strong deflection loads. Imagine that such a board lies freely on the floor with a depression in the middle and a person steps on it. What will happen? That"s right, deflection.

• Now inspect the panel from the sides. There you will see, depending on the side, locks of different types. It is due to them that the panel is held together. Laminate locks are very fragile, since they are made of glued and pressed wood fibers, like the main body of the board. They do not have a protective front coating.
• Now imagine what will happen to a plane assembled from laminate, lying on an uneven base. The deflection, if compared with a separate lamella, will become much smaller, due to the fact that everything is connected with locks, that is, they take on most of the mechanical load.
• If you start to intensively use such a coating, then the locking connections will begin to weaken. If the unevenness of the floor is large, then with a high degree of probability the locks can break, visible seams will appear on the coating, which will increase the thermal expansion of the material and moisture, which will inevitably get inside when washing the floors.

In general, such a coating will serve extremely little, and a high class of coating will not save, since it is only on the front surface of the lamellas. Therefore, there can only be one conclusion – leveling is necessary, and you should not think that this will take a lot of money. Believe me, the price of damaged laminate and your nerves is much higher.

Within the realm of concrete floors beneath laminate, there exist multiple techniques to attain a uniform surface, each with a unique methodology but striving for the same ultimate outcome. Whether you choose to use plywood underlayment, floor grinding, or self-leveling compounds, the objective is always the same: to make sure your laminate flooring has a level and sturdy base. Every technique has benefits and things to keep in mind, like how quickly it can be applied, how economical it is, and how well it works with various floor types. By being aware of your options, you can select the one that best suits your needs in terms of time, money, and flooring, and in the end, you’ll have a level concrete floor that looks good and supports a long-lasting laminate finish.

Methods for leveling a concrete floor

Now that we are positive that a concrete floor must be prepared for laminate, let’s look at the best way to go about doing it. If you have the required equipment and adequate physical condition, you can perform all of the techniques we will discuss with your hands.

Alignment due to screed

Most likely, this approach will be among the first that springs to mind. Although cement-sand screed is a dependable solution, it does require a great deal of labor and experience; otherwise, the finished product might not be significantly smoother than it was initially.

• In addition, it is worth remembering that this solution is quite material-intensive and it is advisable to use it with base differences of 2 centimeters.
• The minimum layer of new concrete coating will also be the same 2 cm, that is, in places of depressions the thickness of the poured layer will already be 4 cm. However, the relative availability of components partially offsets the overspending.

• So, for work you will need the following set of tools: a good building level (it is more convenient to work with a bubble level, since all measurements will be visible directly on the beacon), a rule, a container for mixing the solution, a mixer or a concrete mixer (the second option is acceptable, perhaps, only for a private house), a trowel.

• If available, then we will use a vibrating screed so that the surface turns out perfectly smooth and durable.

Among the supplies you’ll need:

• Beacons – perforated options made of galvanized metal are suitable, but provided that the differences are not very large. If the screed layer is impressive, then it is better to buy several rectangular pipes of the appropriate length.
• Means than to fix the beacons. The easiest way is to use alabaster, but working with it without experience is difficult. As an option, gypsum plaster mix (takes a long time to dry), clips on self-tapping screws, as shown in the photo above, ordinary dowel screws will do.

• Cement – sand concrete grade M150 is suitable for floor screed, the recipe for which we showed in the picture above. In addition to cement, we purchase the required amount of sand and crushed stone, you can do everything on sand or sand and gravel mixture, the corresponding recipes can be easily found on the Internet.

• If the work is carried out in a room where it is not possible to place heaps of bulk concrete components, then it is most convenient to purchase a ready-made cement-sand mixture (CSM) and mix it in a container, only adding the required amount of water specified by the manufacturer.

Counseling! Buying a ready-made mixture ensures that the concrete recipe will be strictly followed, leading to a high-quality outcome. Furthermore, the mixtures (details are in the packaging instructions) have plasticizers and other additives like fiber reinforcement (expensive high-strength options), hydrophobicity, and frost resistance.

The process of pouring the screed

Now, imagine that we have to work from an apartment and that, being sensible and practical individuals, we bought pre-made mixtures as a material. Let’s see if the task is as simple as they typically describe it on numerous websites.

• First, we need to carefully prepare the old base.

Take note! Remember that the steps needed to prepare the base, which we will call now, are not all that different from those needed for other leveling techniques. If there are any nuances in the future, we will just highlight them rather than restating the entire process.

• First of all, completely clear the room. The floor should be open, nothing should interfere with the work. If the situation is such that, for example, there is a 2-ton piano that cannot be taken out, then get ready for work divided into several stages.

• Sweep the floor thoroughly, or better yet, vacuum it. The absence of dust will ensure better adhesion to the surface, and it is simply more pleasant to work in a clean room.
• Ideally, especially when installing on a warm floor system, a technological gap should be left along the edges of the concrete screed for thermal expansion. It should not be large, 3-5 millimeters will be enough.

• To provide the necessary gap, a damper tape made of foamed polymers is used. As an option, a polyethylene underlay for laminate, cut into strips of 5 centimeters, is perfect.
• The tape is stuffed around the entire perimeter of the room using a construction stapler.

That’s interesting to know! The tape will, among other things, stop the walls from absorbing moisture from the concrete, strengthening the screed’s edges.

• If the thickness of the screed is close to 4 centimeters, then you can do without the tape.

• The next step is to apply a primer. Most often, an acrylic-based primer is used – it is both inexpensive and quite effective. Such compositions reduce the absorbency of the base and strengthen it, penetrating into the structure.
• If the condition of the surface is in doubt or the old floor has a layer of paint to which the new screed will not adhere well, you will have to use concrete contact.

• Such compositions contain quartz filler of various fractions, which, when dry, gives a strong rough surface.
• The moment that we missed. Before starting to prime the entire surface, it is necessary to inspect the condition of the old concrete for damage. We are not interested in small cracks, but the gaps between the slabs, into which the solution can sag, should be sealed in advance.

• If the screed thickness is 5 centimeters, then the base can be left unprimed, but covered with polyethylene film. In this case, it is recommended to reinforce the internal space with a mesh, which will significantly increase the strength.

• Next, we begin to set up beacons that will determine the evenness of the future plane. First of all, we check the floor with a level, determining the highest point. As you remember, the screed layer in this place should be at least 1 centimeter, and preferably 2, so we will count the level from here.
• Beacons can be installed alternately, or with intermediate filling. The second method seems to us more correct and accurate, although, as you are used to.
• What is the inconvenience of working with perforated beacons? The fact is that they are very thin and bend easily, especially 6-millimeter options. Because of this, it is very easy to make inaccuracies, which will entail the curvature of the final surface. Therefore, we recommend taking only 10 mm beacons.
• We determine the line of the beacon location and apply gypsum mortar along it in small piles, with a step of 40-50 centimeters.
• We place the beacon on top and set it horizontally, smoothly sinking it with a flat rail (building level). The rest of the beacons are also installed, which together should form a plane, therefore constant control is carried out with a rule applied along and across.

• Excess gypsum is removed from the beacons on top, and it is left to dry. The photo above shows how the beacons stand on very high gypsum bosses. We wrote that this should not be done and here"s why. If you leave it as is, then when pouring in those places where there is no gypsum, the beacons will bend when pulled, and quite noticeably. This would not be very critical when laying tiles, but laminate is a different matter.
• Nobody will want to fill the entire space under the beacon with plaster either, as this is an overspending of material. It will be much easier and more reliable to apply steel rolling pipes, which, lying on the same bosses, will relieve the danger of deflections. At the same time, the price of a meter of such a pipe does not exceed 70 rubles, and it can come in handy later in some other matter.

• Next, go to the shutter of the mixture. Pour the desired amount of water into the container, and then pour the contents of the bag. Following the standard instructions, we mix everything well with the machine method (punch with nozzle), wait 2-3 minutes and repeat the stirring.
• The mixture is ready for work. We overturn the battery, pouring the contents to the floor, starting from the far wall, and moving to the exit. Distribute everything carefully with a trowel, after which we stretch the mixture by the rule.
• You need to pull it slowly, moving the rule from side to side and on yourself. At the same time, it must be held strictly perpendicular to the floor, without tilting, otherwise the instrument itself may play and bend.

Counseling! Verify that the beacons are free of any layers. Throughout, their upper portion should be visible. Iterate the manipulation using the rule until the smooth surface is fully filled. Place mortar where there are voids and dips, if needed.

• While the concrete still retains a liquid state, the surface of the screed can be passed with a vibrating beam. This will allow you to compact the mixture and not level everything perfectly with a rule, since it will take the level and smooth itself out. The main thing is to monitor the absence of subsidence and add concrete as needed.

The concrete screed is poured and then allowed to dry. In extremely hot conditions or in cases where the base absorbs moisture rapidly even after priming, you will need to give the concrete special attention for a while. This will involve wetting it down with water on a regular basis and applying a dark film to the areas that receive direct sunlight.

You can already walk on the screed after a day. After removing the beacons, we use the same solution to seal the debris-filled grooves and clean them.

If you lay laminate over a concrete floor, it should be done within a week or two at the latest, as moisture that escapes can damage the finished floor covering.

Dry screed

If breeding dirt isn’t your thing, there’s always the more contemporary option of dry screed. Prepare to pay for convenience because these floors are more dependable and simpler to make.

To put it into practice, you will require:

• Beacons (pipes or slats);
• Damper tape;
• Building level;
• Gypsum fiber sheets (GVL);
• Expanded clay backfill;
• Waterproofing film.

There are multiple stages to the work’s completion:

• The base is cleaned of dirt and dust, all cracks in it are sealed.
• Markings are made that show the level of the finished floor.
• The base is covered with polyethylene film, which will protect against water. The insulation strips are laid overlapping, and the joints between them are best sealed with tape. The perimeter of the room is covered with a damper tape.
• Beacons are installed. The installation principle is absolutely the same, except that the distance between them can be made large, since expanded clay is much easier to stretch than concrete, which means that it will not be possible to bend the beacons or the rule.

That’s interesting to know! In this instance, the beacons won’t be used again and will stay inside the floor.

• The free space between the beacons is filled with expanded clay. It is very easy to do and you do not need to mix anything. The bags are quite light (18.7 kg with a volume of 40 liters), so you will not have to strain yourself too much.
• Then the expanded clay is pulled with a rule – everything is simple and extremely clear.

• Special gypsum fiber sheets are placed on top of the expanded clay, which have grooves along the edges for joining. The sheets are screwed together using these grooves.

This kind of floor has an advantage in that you can walk around it as soon as the sheets are laid. Moreover, since no water is needed for the process, laminate can be quickly installed over a concrete floor—well, not quite concrete.

Self-leveling floor system

It is advisable to use both of the aforementioned floor-leveling techniques when there are significant differences. However, what should be done if the unevenness is less than one centimeter? The solution lies in self-leveling mixtures, also known as self-leveling floors.

This approach will be referred to as the best for a number of reasons:

• Firstly, the mixture layer is allowed from 1 to 10 centimeters;
• Secondly, the surface that is obtained in the end is very durable and does not dust;
• Thirdly, the floor dries very quickly;
• And fourthly, the work is done faster.

Perhaps the most notable drawback is that it is more expensive than a screed, though this is not a huge difference. Additionally, there may even be a savings if we take into account that this minimum layer is smaller.

Thus, the pouring is done in the order listed below:

• The base is cleaned and carefully inspected for cracks. Due to the fact that self-leveling mixtures have high fluidity, they can go even into the smallest holes, so all suspicious places are carefully coated with plaster.
• At the exit from the room, a piece of metal profile is screwed to the floor to prevent leakage of the mixture.

Advice: It is advised to use the same profiles to create divisions in a room that is too big.

• Then the floor is carefully primed. It is best to use concrete contact for this.
• Next, beacons are installed – here they are somewhat different.

• Masters use these tripods, which have a movable rod in the center, the lowest point of which will show you the level.
• Using the technology already described, we look for the highest point and place the first tripod on it. Lower the rod – the distance from the floor should be 1 cm.
• Using a laser or bubble level, we place the remaining beacons in different parts. At the same time, when setting them up, we work with the upper point of the device, on which there is a convenient platform. The number of beacons is determined at the request of the master, but the more there are, the more accurate the result will be.
• Mix the mixture in two containers at once so that the process goes on continuously. Two people need to work – one pours, the other kneads. If you take breaks, the mixture may not spread normally.
• Pour the solution onto the floor and roll it with a needle roller to remove air bubbles. The site will be leveled when the mixture on it is equally suitable for all beacons.

Suggested! Avoid pouring all at once to avoid creating layers that will eventually cause the floor there to rise above the level. If the floor is already level, do not pour the mixture there. Take care to fill the designated level to the fullest.

After two to three hours, you can walk on high-quality cement-based self-leveling floors. However, before you do, make sure that everything has solidified, as the type and quality of the base greatly affects how long the setting takes.

Method	Process
Self-leveling Compound	Pour and spread the compound to even out the floor surface.
Grinding	Use a grinder to smooth rough spots and create a level base.

There are a few different approaches to leveling a concrete floor under laminate, but they all lead to the same end result: a level and smooth surface for your flooring. Depending on the state of the existing concrete and the schedule of your project, there are benefits to using self-leveling compound, grinding, or plywood underlayment.

Self-leveling compound is a preferred option due to its rapid creation of a smooth surface and ease of application. It is perfect for small unevenness in the concrete because it flows into low areas and levels itself. To achieve a satisfactory result, this method necessitates precise pouring and mixing along with careful substrate preparation. After curing, the floor provides a level and stable base for installing laminate.

Another useful technique is to grind the concrete floor, particularly if there are larger imperfections or high areas. This procedure involves leveling out uneven spots and bumps with a specialized grinder so that the surface is ready for laminate. Compared to using self-leveling compound, grinding can be more labor-intensive and dusty, but it gives you precise control over the leveling process and can fix deeper imperfections.

If there are small irregularities in the concrete floor and you would rather not change the current surface, using plywood underlayment is a practical solution. After making sure the floor is dry and clean, plywood sheets are placed on top of the concrete. This simple technique can improve the performance and comfort of your laminate flooring by protecting against moisture and providing insulation.

The technique you decide on for leveling your concrete floor beneath laminate ultimately comes down to the particulars of your project and how you want it installed. Self-leveling compound, grinding, and plywood underlayment are three dependable methods that help you achieve a level and stable surface so your laminate flooring looks and functions at its best.

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