Concrete screed on a wooden floor: if it is impossible, but really necessary

Mixing materials when renovating a home can occasionally result in unforeseen difficulties. The idea of applying a concrete screed to a wooden floor presents one such difficulty. This may seem like a bad idea at first because of the differences between concrete and wood. Nonetheless, there are circumstances in which it becomes essential. Knowing how to apply concrete over wood properly is essential, whether you’re trying to level an uneven surface or create a sturdy base for new flooring.

Wood is renowned for its natural flexibility and ability to expand and contract in response to temperature and humidity variations. Conversely, concrete is stiff and doesn’t adjust well to these changes. If not handled properly, this fundamental difference can cause cracks and structural problems. Despite these difficulties, a sturdy and long-lasting concrete screed over a wooden floor can be accomplished with the appropriate methods and supplies.

Before starting any kind of project, it is important to prepare. After giving the wooden floor a thorough cleaning, any loose or damaged boards need to be replaced or fixed. Wood warping can be avoided by controlling moisture levels and installing a vapor barrier or layer of insulation. In addition, movement can be accommodated and the likelihood of screed cracks is decreased by utilizing a flexible membrane between the concrete and wood.

Selecting the proper kind of concrete mix is also crucial. Improved adhesion and a lighter screed mix can lessen the overall load on the wooden structure. A more stable outcome can be achieved by improving the bond between the concrete and the wooden surface by applying a bonding agent. A concrete screed on a wooden floor can offer a strong, long-lasting foundation for your home renovations with proper planning and execution.

Problem	Solution
Wooden floors can flex and move	Use a flexible membrane to separate the screed from the wood
Moisture can damage wood	Apply a waterproof layer before laying the screed
Weight of concrete can be too heavy	Use a lightweight screed mix
Cracks in screed due to wood movement	Install reinforcement mesh within the screed
Poor bonding between wood and screed	Use a bonding agent to improve adhesion

Specifics of a wooden base

The aforementioned materials exhibit entirely distinct behaviors. It is a very practical situation to have a wooden floor laid on top of a concrete screed. After reaching its maximum strength, concrete turns into a static base, while wood is a living, breathing material the whole time it is in use.

Take note! The first four years are particularly active for wooden floors. You shouldn’t even consider covering the boards with concrete during this time.

Variations in the room’s humidity and temperature have an additional impact on wood. In addition to changing linearity, the boards’ volume and height can also change.

The situation where wood is poured to arrange warm floors can be characterized as the subject of a different article. The number of variables rises sharply in such a scenario. Taking into account the characteristics of wood, the following crucial deduction can be drawn:

The screed, a wooden-base device, needs to be self-sufficient. It is not advised for the materials to come into contact while the device is operating, as this could cause damage to each layer’s characteristics.

Preparation for pouring

A wooden floor may have a different device. Don’t be lazy: remove the wood and apply a rough screed if the boards are nailed to logs that are fixed to a concrete base. Additionally, you’ll receive a floor that is more resilient and trouble-free going forward.

If your base is made of boards, it is also best to keep the finishing layer and logs out of the floor cake device as this will reduce the base’s mobility. Take down the skirting boards and any other ornamental pieces prior to preparation.

In order to proceed, the plank base needs to be ready:

• Secure all playing elements, the flooring should become as rigid as possible.
• In case of flooring deflection, it should be reinforced with cross guides.
• The floor should not have any height differences.
• All damaged elements should be replaced before pouring.

Because concrete has a higher weight, the logs must have a sufficient load-bearing capacity; if needed, this means adding more of them. A step of 35 cm +/- 5 cm should ideally separate the beams.

After being fixed, swapped out, secured, and processed. Selecting primers with antibacterial and waterproofing qualities will help you stop the structural elements from deteriorating.

Waterproofing

We will be able to separate the materials from one another thanks to this event. As a result, a robust polyethylene film with the greatest possible width is chosen. Avoiding glueing the poured surface’s seams is preferable.

Crucial! When laying the film, take caution because breaks and punctures are not acceptable.

The film is applied to the wall in an overlapped pattern, and damper tape is used to adhere it all around. Because of this, when you pour, the concrete slab will float and not come into contact with the walls or base material. The concrete will be at rest in this scenario, meaning it won’t crack and will maintain its linearity, and the tree can carry on with its active life.

Why film?

Since the wood beneath the film will eventually start to rot, this question seems to be very important. Other waterproofing materials, such as parchment, roofing felt, or something impregnated with bitumen, are typically used when working with such structures.

The movie is chosen for concrete rather than wood. Polyethylene is not at all adhered to by the solution.

A triple floor pie is created by sandwiching polyethylene between concrete and wood, with each layer functioning completely independently of the other:

• Both the wood base and the rough screed can move along the insulation;
• The concrete will not pull the film along with it and will not tear it;
• The solid polyethylene will not allow the wood to draw moisture from the concrete.

Crucial! Apply a waterproofing primer to the boards to reduce the harm that polyethylene will do to them.

Pouring technology

Once we understand the fundamentals of how a concrete screed should be laid out on a wooden floor, we can begin the pouring process. Assign a random zero level to each of the outer walls.

With any building level, this is easily accomplished. If the zero level is marked between 0.4 and 0.7 meters above the floor, it will be more convenient. We mark the entire perimeter and drop the same amount of material from the line. This will be the screed’s maximum height.

Take into account the following factors when determining the height of the concrete screed:

• Thickness of finishing material. This is especially important if you plan to screed under tiles on a wooden floor. In this case, it is worth considering the thickness of the tile itself and the adhesive layer.
• Mass of concrete. As a result of screeding with concrete, a heavy structure will be obtained, so it must be taken into account that a 10 mm layer of concrete will give an average weight load of 110 kg/m2. Not every wooden flooring can withstand such a load.

Isolation measures

It is necessary to remove any chance of wood and concrete coming into contact. This is accomplished by adhering damper tape around the entire circumference prior to filling. The strip’s width ought to be a few centimeters wider than the screed’s thickness.

• After completing the filling and installation of the finishing decorative layer, the protruding excess tape is cut off.
• The resulting technological gap is covered with a plinth.
• After the floor is prepared and the level is set, we lay the film.

• Do not skimp on material for going onto the walls – then you will carefully cut everything off. If joining seams cannot be avoided, their width should be at least 10 cm. The seams must be glued as tightly as possible.
• It is very important to lay the film evenly, without folds. Gaps, punctures, and holes are also unacceptable. All subsequent activities are carried out with the utmost care so as not to damage the integrity of the film.
• If the film is still torn, apply a patch in the same way as gluing the seams.

Reinforcement

It is best not to use a metal reinforcing mesh at this time.

This is for a number of very valid reasons:

1. Metal reinforcement will most likely tear the polyethylene, which is absolutely unacceptable.
2. Steel is a very heavy material, and will further increase the weight load on the wooden flooring.
3. The middle layer of concrete should be reinforced, which means that ideally the pouring should be done in 3 stages: pouring-reinforcement-pouring. Such a procedure will take exactly 56 days, taking into account the complete drying of all layers.

In light of the drawbacks, we decided to replace the metal mesh with fiber. The process of adding fiber reinforcement is depicted in the picture below.

Before pouring, the fiber needs to be incorporated into the mixture. The work will be completed faster, lighter, and with a more dependable connection in any direction if the polymer particles are arranged randomly. Depending on the thread thickness, the fiber’s properties change.

Pouring the solution

The method for screeding beams is the same as for any other rough screed.

• each room is poured separately,
• the layer is poured in 1 stage,
• work is carried out starting from the far corner of the room towards the exit,
• if the area is large, the surface is divided by guides or formwork.

Pre-installed beacons are used to determine the coating’s leveling.

• Beacon profiles are attached to cement mortar.
• It is unacceptable to use gypsum compositions for installing beacons.
• After 24 hours, after the main stages of work are completed, the beacon profiles should be removed and the unevenness repaired. The video in this article will help you to become more familiar with the pouring technology.
• Do not allow the coating to dry quickly, regularly wet the surface with water. This will help to avoid cracks.
• It is best if the screed gains strength while under a polyethylene film.

Maintaining a steady environment in the space is essential, including maintaining the right humidity and temperature.

Concrete volume calculator

Options are possible

If you’ve already determined that concrete screed on logs is necessary, think about other pouring options to increase your options. Of course, concrete is more affordable, but it is heavy and challenging to mix properly in terms of proportions.

The qualities of various materials that can be used for wood screeding are contrasted in the table below:

Consider all of the benefits and drawbacks as well as your options before making a decision. You can work with wood on certain self-leveling floor mixtures to create smooth, long-lasting surfaces that don’t mind high humidity.

Epoxy mixes, for instance, are used to create self-leveling flooring surfaces that are impervious to both chemical and physical forces. The manufacturer provides installation instructions for self-leveling floors on the packaging.

There are circumstances in which concrete screed cannot be avoided, despite conventional wisdom’s recommendation to avoid it on a wooden floor due to possible problems like moisture damage and structural incompatibility. A sturdy and stable screed can be obtained by comprehending and putting into practice the right methods and safety measures, such as applying a separating layer and making sure there is enough ventilation. This method preserves the integrity of the wooden subfloor while providing a stable, level surface.

Calculation of concrete composition

Laying a concrete screed over a wooden floor may seem difficult, but it is doable with the appropriate technique. The secret is to deal with the peculiar qualities of wood, like its pliability and propensity to expand and contract in response to variations in temperature and humidity.

Making sure the wooden floor is secure and stable is crucial first. Prior to continuing, any loose or creaking boards need to be fixed. Furthermore, it is essential to have an adequate moisture barrier to stop wood from absorbing moisture from the concrete, which over time can cause rot and degradation.

It’s also advised to place a decoupling layer between the concrete screed and the wood. This layer helps to prevent cracks and other problems by allowing the concrete to set and harden without being directly impacted by the movements of the wooden floor.

Through meticulous floor preparation and implementation of appropriate safety measures, it is possible to apply a concrete screed with success and accomplish a long-lasting and robust finish. This technique creates new opportunities for remodeling and improving areas with wooden floors that require a stable, level surface.

Video on the topic

Screed on a wooden floor. Concrete screed on wooden beams.

Screed on a wooden floor. Will it save you from vibrations?

Screed on a wooden floor.Tiles on a wooden floor

Floor screed in an apartment. Pros and cons of concrete floors

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