Which is better to choose polystyrene foam for screeding and how to carry out installation work correctly.

Selecting the appropriate screeding material is essential for building and remodeling projects. Because it is lightweight and insulating, polystyrene foam has become more and more popular, making it a popular option. There are a few things to consider when determining if polystyrene foam is right for your project.

Expanded Polystyrene (EPS) foam, commonly referred to as polystyrene foam, provides exceptional moisture and heat resistance, making it useful for a variety of applications, including screeding. In comparison to more conventional materials like concrete or mortar, its lightweight nature facilitates handling and installation.

Make sure the surface is dry, clean, and free of any debris that could interfere with adhesion before starting the installation. The secret to getting a screed that is strong and long-lasting is proper surface preparation. Polystyrene foam comes in a variety of grades and densities, depending on the particular needs of your project.

Assembling polystyrene foam for screeding requires adherence to manufacturer recommendations and best practices. To do this, you usually need to apply a mortar or adhesive that will hold the foam sheets firmly in place. A level surface is important because any irregularity can impact the screed’s performance and final finish.

As directed by the manufacturer, give the mortar or adhesive enough time to set and cure after the polystyrene foam is installed. Applying the screed material can start as soon as the foam sheets are firmly in place. To protect the foam and guarantee that the screed layer is the same thickness throughout, this procedure needs to be carried out cautiously.

By selecting polystyrene foam for screeding and using the right installation methods, you can create a level and smooth surface while improving your building’s thermal efficiency. To find the best kind and thickness of polystyrene foam for your particular project needs, think about speaking with suppliers or construction experts.

The main thesis statement for the article "Which is better: choosing polystyrene foam for screeding or understanding its benefits and proper installation techniques?" could be: Understanding the benefits of polystyrene foam and how to properly install it is essential to achieving effective insulation and structural stability in construction projects. This article examines the benefits of utilizing polystyrene foam, evaluates the various varieties that are available, and offers helpful advice on how to install it correctly to guarantee the best possible results for construction and remodeling projects.

The advantages of this solution

Trading floors may contain polystyrene foam in the form of slabs or granular mass. Because they are easier to work with, the first ones are typically laid beneath the screed. However, backfill is not the least common type of heat insulator.

Polystyrene foam offers numerous benefits when used for the floor beneath a screed. Among them, the following merits special attention:

• low weight due to high air content due to the foam structure;
• porosity explains the ability of a material to provide effective resistance to heat loss;
• a large number of walls between the cells provides vibration damping, which has a positive effect on the acoustic properties of polystyrene samples;
• the closed-cell structure and polymer base together do not allow water and vapor to penetrate into the material;
• the insulation, which is synthetic in nature, depending on the additives and density, is flammable to varying degrees, but in any case retains the ability to extinguish on its own (therefore, polystyrene foam is not used on objects with a high fire hazard).

To prevent pouring deformation, foam with a density of more than 25 kg/cube.m is advised for floor screed. The technical specs of two workable examples are displayed in the table.

* The polystyrene foam minimum tensile strength is displayed in the table.

**The indicators are accurate when the temperature is +25 degrees Celsius and the relative humidity is within 65%.

*** The indicators hold true for daily testing of a specific sample when it is fully submerged in water (calculated as a percentage of the workpiece’s total volume).

Let’s look at which polystyrene foam, in terms of thickness, is better for the floor beneath the screed. The selection of the value ought to be predicated on the subsurface conditions. Generally, it is sufficient to have a polystyrene layer 30 mm high above a heated room. It is preferable to lay slabs that are 50 mm thick if the temperature falls below +10 degrees Celsius. Furthermore, the figure rises to 70 mm above the basement, where the temperature is lower.

Installation work

There are two methods for insulating floors with polystyrene foam underneath screed: soft base and hard base. Slabs are laid on top of compacted soil or sand in the first option. Boardwalk is included in this as well. A previously poured rough concrete floor or a dense, pre-formed two-layer backfill made of sand, fine gravel, and clay constitute the second type of base.

Foundation requirements

Backfilling polystyrene foam beneath a floor screed is a straightforward process. It ought to be one level, as compacted and level as feasible, according to the design. Large protrusions, such as ridges, bumps, and leftover tile adhesive or old finishing, must be removed if the floor was previously concreted. Because the slabs are naturally brittle, this is required to guarantee that they do not fracture while in use. The screed will eventually collapse due to the deformation of the foam.

Protective measures

The floor needs to have a waterproofing coating applied, regardless of the type of base. But material selection is important. For instance, it is preferable to use a coating-type composition to keep wood from getting wet. Additionally, a 200 micron-thick plastic film is adequate to cover the concrete. The only possible exceptions are slabs of extruded polystyrene foam with multi-level mounting edges and backfilling on clay-containing soil. Plates of this type are gathered "in the castle." The water in the solution won’t evaporate too quickly only in this situation.

Let’s go back to the waterproofing decision. The foam used for floor screed or other problems doesn’t differ in terms of its resistance to organic solvents and generally similar-looking compounds. It is therefore worthwhile to start with just water-based samples. It is necessary to wait for bitumen mastic to completely dry out if it is chosen nonetheless. Additionally, covering it with a technical film is worthwhile. Its thickness ranges from 100 to 150 microns.

It is important to note that many experts advise applying a film to the polystyrene underneath the screed. The explanation for this is straightforward: since she won’t have anywhere to go, water will easily seep through the seams, creating an environment that could be favorable for microorganisms. Both the waterproofing and the foam itself are unlikely to encourage the active growth of fungi and bacteria. However, they can exist in water, proliferate in moisture, and eventually demolish nearly any substance. Furthermore, water will exit the solution too soon due to the cracks. As a result, the screed will be of lower overall quality and insufficient strength.

Additionally, it’s important to shield the upcoming screed from any harm that might result from the floor and walls interacting. Even though thermal expansion might not be seen, it has the potential to cause harm if two structures come into direct contact with one another. Consequently, the "floating" method is used to form the screed. Additionally, a plastic damper tape is installed to close the space between the floor and nearby walls.

Laying insulation

Here, everything is easy. The screed should be placed on a mostly monolithic foam layer on the floor. When maintaining a significant thickness is required, forming a two-layer coating is advised. Here, the sheets are arranged with offset seams between each other and in a row (the second one relative to the bottom one). The initial production of extruded polystyrene foam typically includes mounting edges, which streamlines the floor insulation process overall.

A common preference is to use an adhesive solution to fix the slabs. Applying a thin, even layer with a comb, the workpieces are lightly pressed against the ground and one another. Wide-headed special dowels are an additional choice. They are frequently referred to as "thermal insulation attachments." This process is quick, easy, and mess-free. However, areas containing fasteners need to be sealed off from water infiltration before pouring.

Fill

A screed layer no thinner than 50 mm is advised for floors made of polystyrene foam. Such a coating doesn’t always require compression strengthening when applied to solid bases. Polystyrene foam, however, is not. Consequently, a metal mesh made of welded steel rods with a 4-5 mm cross section is typically placed on top of the film. Square cells can have side lengths between 100 and 150 mm. A "warm floor" system, which is intended to be installed in the screed layer, can be installed at the same time.

Next, beacons are put in place. They have to be strong and able to hold their position consistently. The rule is used to level the solution. After that, all that’s left to do is wait for the screed to dry fully before moving forward with the finishing.

The best choice for "water" floor heating is determined by comparing foam and extruded polystyrene in this video:

It’s crucial to take your project’s type and thickness into account when selecting polystyrene foam for screeding. Extruded polystyrene (XPS) and expanded polystyrene (EPS) are popular choices with unique benefits. Since moisture isn’t a big concern, EPS is a cost-effective and lightweight material that is perfect for leveling floors and insulation. However, XPS has a stronger compressive strength and is more resistant to moisture, which makes it ideal for moist environments like bathrooms or basements.

Make sure the surface is dust-free, dry, and clean before installing. Apply a suitable primer first to aid in adhesion. Trim the polystyrene foam boards so that there are as few spaces between them as possible. Assemble the boards securely and levelly on the floor by using the suggested adhesive.

After the boards are installed, use mesh or tape to strengthen the joints to stop cracks during the curing process. As per the manufacturer’s instructions, you might have to wait for the adhesive to solidify before moving further. To create a smooth and even surface, cover the foam boards with a self-leveling compound afterward.

Lastly, give yourself enough time to dry completely before adding any more finishes or floor coverings. This procedure guarantees the longevity of your polystyrene foam screed, improves the overall comfort and energy efficiency of your area, and offers efficient insulation.

Video on the topic

Thermal insulation of heated floors. Why is density important?? Why not polystyrene foam??

NEVER fill a screed like this for a water heated floor

"Penoplex foundation" for heated floors. Installation errors.