How to apply plywood adhesive to a concrete floor when installing a subfloor

Advantages of plywood

Plywood itself is a material consisting of several thin layers of veneer. It has a wide range of useful characteristics, which is why it is so widely used for laying on concrete floors.

The main advantages of this material are:

• A smooth and even surface is an ideal option for any floor covering. It allows you to completely hide the flaws of the concrete base. Subsequently, laminate and parquet, linoleum and carpet can be laid on plywood.
• The reasonable cost of the material allows it to be used by a wide range of consumers.
• Ease of processing and installation.
• The soundproofing properties of plywood enable the owners of the premises to isolate themselves from the penetration of excess noise from neighbors.
• Water resistance. However, for rooms with high humidity it is better to use special sheets marked FSF, which have high water-repellent characteristics.
• Leveling a concrete floor with plywood is a neat and clean job, unlike pouring the same cement screed.
• Environmentally friendly material.
• Excellent wear resistance and strength.

How to lay plywood on a concrete floor

Apply two-component or regular adhesive to the cement screed in an even layer, approximately 2 millimeters thick. For this, a notched trowel is used, which allows you to apply the adhesive composition as evenly as possible and determine the required amount of glue.

USEFUL INFORMATION: Window in the bedroom: decoration and design

After laying the plywood sheet, it must be rolled with a heavy roller. When using regular glue, you should use additional fasteners - dowels or screws. However, there are certain rules that must be followed while working:

• Plastic dowels and metal screws should be located at a distance of 15-20 centimeters from each other.
• The fasteners must be fixed around the perimeter of the square.
• The self-tapping screw must be more than three times the thickness of the plywood sheet.

Holes in the concrete are drilled through plywood sheets at the fastening points to the required depth. Plastic dowels are inserted there and a self-tapping screw is screwed in.

After fixing them, they should be sanded using a special sanding machine for parquet. But now there are sheets of plywood on sale that are sanded on one side, which will save you from unnecessary work. Only then can you begin laying the decorative flooring material, which will be the final, finishing touch in the floor repair work.

Types of suitable glue

There are many adhesive compositions on the modern market. To fasten plywood to a concrete floor, it is important to choose an adhesive that will glue the surfaces well enough, not be afraid of exposure to moisture and other factors, and will ensure reliable and durable fixation.

Polyurethane

This type of adhesive composition is characterized by the highest strength, excellent adhesion to all building materials, does not have a pungent odor, meets all sanitary standards and is recognized as safe by government organizations.

Types of polyurethane glue by composition:

1. Two-component - consists of two parts (direct adhesive and hardener). It is used for fixing lumber on various types of bases, including concrete screed. Only this composition can be used for super-reliable fixation of plywood to concrete and without dowels. They are more expensive than other adhesives, they are used after preparation for 50-60 minutes (and then become unusable as the polymerization process is completed).
2. One-component - not very plastic, polymerization occurs due to moisture in the environment.

Polyurethane can be diluted with different types of solvents, inorganic and organic. In most cases, it is the type of solvent that determines the environmental friendliness of the material and the permission to use it in residential premises.

Based on artificial resins

This adhesive for plywood on concrete floors can also be used and provides good adhesion. It does not require any preparation before starting work and is suitable for gluing different types of lumber. To increase the fixation strength, plywood is also additionally secured with dowels. One of the disadvantages of this glue is its strong unpleasant aroma, so work is carried out using personal protective equipment.

Water based

This type of composition is considered the safest, since it does not contain toxic or strong-smelling components. The price of the glue is relatively low, but the level of adhesion is lower in comparison with the above compounds. The adhesive is designed for use inside heated rooms, but the plywood must be moisture resistant.

The most popular example of a composition of this type is water-dispersed PVA glue. Its main advantage is that it does not lose its properties even if the substance is applied to a damp screed. The glue guarantees the plasticity of the connection, dries for a long time (within 5-7 days), but requires mandatory fastening of the material with dowels.

Advantages of attaching plywood with glue

Plywood is good for leveling the base

Most finishing floor coverings (laminate, parquet) require installation on a perfectly flat surface.

Laying plywood provides:

• fast preparation time for the foundation;
• a flat surface is obtained that serves as a substrate for the finishing flooring;
• additional sound and heat insulation;
• affordable cost of material;
• good adhesion with adhesives.

Fastening sheets of plywood with glue allows you to get a strong and reliable base.

Application of glue does not require construction skills or special equipment.

Many adhesive compositions can be used in rooms with high humidity and when installing underfloor heating systems.

Correctly selected adhesive for plywood on a concrete floor guarantees tight fastening of the material and a long service life.

Features of choosing glue

Depending on the finishing floor covering

When choosing an adhesive for gluing plywood to the base of the floor, you need to start from the material of the latter and the conditions for further use of the room:

• When deciding how to glue ceramic tiles to a wooden floor, you will need tile adhesive for plywood that does not include water and is not aggressive towards wood.
• If you need parquet adhesive for plywood on a wooden floor, you should choose between epoxy-polyurethane or pure polyurethane systems containing artificial resins and solvents.
• To glue linoleum onto plywood, you need an appropriate adhesive that can provide a long-lasting, strong seam. It is affordable, safe and approved for use in residential areas.

Laminated plywood (with a film coating) cannot be glued. Therefore, before applying the epoxy compound to it, the film must be removed from the surface with sandpaper.

For unveneered plywood

After gluing to the screed, plywood can be either an independent coating or simply serve as an intermediate layer for the finishing coating.

For unveneered plywood, you can use any glue. The only important thing here is that its surface is clean and dry. The adhesive can be applied evenly with a roller or brush to both surfaces to be bonded. Long-curing adhesives require preliminary fixation of plywood sheets to the screed using dowels, nails or clamps after approximately 30-40 cm. After work, excess mixture must be removed along with unnecessary nails.

Suitable types of glue

What is the best adhesive for installing plywood on concrete floors? Let's look at several options that have their own positive and negative qualities.

Dispersive

Container with water-based adhesive solution

The components of this glue do not dissolve, but are located and mixed in a water-dispersion medium. This structure ensures the environmental purity of the solution, due to which only absolutely harmless and odorless water molecules evaporate during the solidification process.

But you should also be aware of the difficulties that arise when using a water-based adhesive:

• The need for additional fixation with steel screws and plastic dowels.

Advice: if communication elements are located in concrete, then without a detailed diagram of their location, you should abandon the use of dowel-nail fasteners. Because you can damage the wiring, after which you will need to cut reinforced concrete with diamond wheels to get to the breakdown and eliminate it.

Diamond drilling of holes in concrete for repair of underground communications

• A long curing period of at least one week.

Before use, the solution is diluted with water or a special primer. Consumption is approximately 1.2 kg of glue per square meter of concrete.

Alcoholic

Sample of alcohol adhesive solution

This glue is made on the basis of artificial resins or solvents. The presence of a specific odor forces you to use a respirator during work and thoroughly ventilate the room.

But you will also get many benefits:

• Drying usually occurs within three days under normal conditions.
• The cracks and voids are well filled, which allows you to achieve a higher density of the rough base.
• Remains elastic after hardening, which prevents cracking.

In the case of using this solution, additional fixation with self-tapping screws and dowels for concrete is also desirable. Its consumption reaches one and a half kilograms per square meter of cement surface.

Two-component

Polyurethane two-component adhesive for plywood on concrete floors

The cost of such a composition is higher than that of its analogues, but there are also more significant advantages:

• No additional fastening is required using the self-tapping dowel system. And this is a significant saving of time, money and effort.
• The shortest curing period is two days. That is, after 48 hours you can start sanding the wood-laminated board.
• Highest strength.

It is also important to keep in mind that before gluing plywood to concrete, it must be primed with a special solution to improve adhesive properties and create a protective polymer coating.

Technology for gluing plywood, step-by-step instructions

Before gluing plywood to concrete, you need to check how durable the preliminary coating is. If everything is in good condition, then it is then prepared for the final stage.

Preparation of concrete screed

Before gluing plywood to concrete on the floor, you need to make sure that the surface is dry and free of moisture. To check, an oilcloth is spread on the floor and left there for a day. If there is no moisture underneath, then you can start priming, otherwise it is better to wait.

Important ! You cannot begin repair work if the concrete is not completely dry, this will lead to the adhesion between the materials not being strong enough.

Preparation usually consists of 4 main stages:

1. First you need to thoroughly clean the surface from dirt and dust.
2. The next step is the purchase of glue, mastic, primer and preparation of tools. If you use materials from the same manufacturer, this will ensure better bonding of the materials. It is important to remember that it is advisable to purchase this material in reserve.
3. The primer is applied to the surface with a roller, then distributed in hard-to-reach places with a brush. This way the consumption is less.
4. After the first layer has dried, you need to apply the second and wait until it dries.

Once you've finished working with the primer, you need to move on to the glue.

What tools and materials will be needed

Laying plywood is in many ways similar to the process of gluing ceramic tiles, with the only difference being that you have to additionally cut and cut the sheets into blanks and fix them with dowels.

Therefore, in addition to tools for glue - a spatula, a container for diluting the adhesive mass and a mixer, you will need a small set of carpentry tools:

• A jigsaw, preferably with a built-in laser pointer;
• Sandpaper for manually sanding burrs and plywood edges;
• Construction level 70 cm and 150 cm long, tape measure, set of metal rulers;
• A screwdriver or electric drill with a set of drills, dowels with plastic plugs.

In addition, for installation you will need to make a template to control the width of the joints, buy material for sealing them, primer and the plywood itself. For priming under resin or bitumen mastic, a primer based on white spirit is suitable; in other cases, an acrylic composition can be used.

How to choose the right plywood?

When choosing a suitable material, you need to pay attention to a number of significant nuances that determine the key properties of the sheets and the possibilities of their use. For greater ease of perception, information on this matter is presented in table form.

Table. Plywood selection

FC – characterized by average moisture resistance. To glue layers of material, safe glue based on urea resins is used, which allows you to use the sheets when renovating residential premises without unnecessary fears.

E2. The average formaldehyde content is 10-30 mg/100 g.

How to choose the right plywood

Thus, FC plywood is most preferable for interior work. This material is further divided into 4 groups. The classification is carried out according to the following characteristics:

• external defects are absent or present in insignificant quantities;
• there are knots and veneer inserts;
• the material has a large number of cracks, knots and other flaws;
• the least quality plywood with a very large number of defects. Along with this, the sheets, as a rule, are glued together quite well, which allows them to be used for some construction activities.

Plywood of the last group is practically not used for interior work. Making a subfloor from the highest quality plywood is not financially feasible. Thus, the most optimal option in terms of the ratio of quality indicators and cost is the material representing the second group, which has a small number of knots and veneer inserts.

Types of suitable glue

Glue for plywood on concrete floors is produced with different compositions. Each of them is suitable for the job, but they have some features that are taken into account when attaching.

Polyurethane

The polyurethane series is more expensive, but has excellent strength and elasticity. Once completely dry, it is environmentally friendly.

According to the composition they are distinguished:

• Single-component. It is convenient to use, as it sets gradually during installation, which allows you to level the surface before the composition dries completely.
• Two-component.

Has multifunctional qualities:

• the composition is viscous, it is distributed with a combed spatula;
• rational use;
• the chemical has significant permeability;
• adhesion is not tied to surface cleanliness;
• hardening time occurs after half an hour;
• no additional fixation with dowels is required;
• after complete hardening, a layer stronger than concrete is obtained;
• withstands temperatures up to 50 degrees.

• toxic substances are released during operation;
• Use the prepared mixture within 30 minutes.

An example of a two-component polyurethane mixture is Berger Bond P2X. It is based on high quality polyurethane raw materials. No solvents or water are added to the composition. It is durable before hardening and can withstand heavy loads.

Based on artificial resins

A mixture based on artificial resins has universal use. No additional preparation is required before use. The use of dowels is required to enhance the fixation strength. When working with such adhesives, you must use personal protective equipment for the respiratory system, as it has a strong, unpleasant odor.

Wakol K450 adhesive is solvent based, has good strength, is used for heated floors, and is frost-resistant. When applied, the surface is cleaned.

Water based

This type of mixture is the safest, since the composition does not contain toxic substances available. Adhesion is lower than that of other species. Basically universal. Designed for work inside heated rooms. Requirements for plywood are moisture resistance.

An example is water-dispersed PVA glue. Its peculiarity is that it does not lose its properties when applied to a damp screed. Provides plasticity of the connection. Long drying time (can be 5–7 days). Fastening the material with dowels is mandatory.

Types of adhesives for fixing plywood

Laying plywood on a concrete floor, or rather fixing it, is carried out using special glue. Today, there are several types of adhesives suitable for fixing plywood to concrete:

• Dispersion adhesive is an environmentally friendly product that does not contain harmful additives. It is odorless and has a long hardening time. However, such glue is not capable of providing the maximum degree of fixation, therefore, plastic dowels or steel screws should be used in conjunction with it.

• Water-based glue is the simplest and easiest to use; moreover, it can be used instead of a primer, simply by diluting it with water.
• Alcohol glue has a sharp, specific odor, which forces the craftsman to wear a respirator while working. But it dries completely within three days at normal room temperature. Due to its optimal density, the alcohol-based adhesive perfectly fills gaps and cracks, which ensures the strongest adhesion of plywood to the concrete base. In some cases, additional fastening using dowels is also required.

USEFUL INFORMATION: All about joining linoleum: planks, thresholds, gluing seams

• Two-component adhesive has such remarkable characteristics as the shortest hardening time, excellent strength and the best fixation, in which there is no need for additional fastening.

Advice: no matter what glue you choose to fix the plywood, in any case prime the concrete base with a special solution. This will increase its adhesive properties and create a protective polymer coating.

Laying technology step by step

Installation of plywood on a screed under a parquet board is carried out in six steps. All operations are available for self-production. Minimum set of tools for this:

• markings - ruler, pencil, square, marker;
• cutting - hacksaw, hand-held circular saw, jigsaw;
• installation - spatula-comb with a tooth of 4 - 6 mm, hammer drill, screwdriver, hammer;
• sealing seams - a gun for sealant in tubes;
• finishing - an orbital, belt or vibration sander.

Usually all this tool is available in the arsenal of a home craftsman.

Preparing the base

Before laying plywood, the concrete screed must meet the following parameters:

• unevenness within 2 mm/m²;
• absence of dust, grease stains;
• humidity not higher than 4%;
• no cracks or delamination.

Treating the screed with deep penetration primer.

Before installation, the screed is vacuumed and thoroughly primed; it is advisable to do this the day before installation. When using a spatula with a tooth height of 6 mm to apply glue under the plywood in the following stages, the layer thickness will be a maximum of 3 mm. Therefore, irregularities larger than this size will remain unfilled.

Film screed test for moisture.

Humidity is checked using the standard method - for 12 hours, a piece of plastic film must be secured with tape around the perimeter of the screed for 12 hours. Work can only begin when there is no condensation under the film. Otherwise, the structure needs to be dried naturally additionally. Evenness is checked by the two-meter rule.

Cutting plywood sheets

At the slightest change in humidity in the room, the plywood begins to warp if it is rigidly screwed to the base. Therefore, laying this sheet material on concrete in large pieces is not allowed.

Depending on the size of the slab, you should use pieces with sides of about 60 - 70 cm. For example, a sheet of 122x122 cm cut into 4 parts will have a format of 61x61 cm. And for a sheet of 152.5x152.5, the pieces will have a size of 76.25x76.25 cm, respectively.

Installation of sheets

The prepared pieces of slab material must be glued, then additionally secured with dowel nails, taking into account the following requirements:

• the gap around the perimeter from the wall is 10 mm;
• seam width between sheets is 4 – 5 mm;
• displacement of transverse seams by 2/3 - 1/2 in adjacent rows.

Plywood layout diagram.

You can start gluing from any area, since you can walk on the rough plywood flooring right away.

Laying is carried out in rows, so before installing the first sheet, a line is drawn along its outer edge along the wall.

Then, using a notched trowel, glue is applied to the screed for one sheet of plywood or for a whole row, depending on the qualifications of the home craftsman.

Next, plywood is laid, the distance between its edge and the wall is 10 mm.

Installation of the first sheets.

Rows of holes are drilled for dowel-nails with a pitch of about 200 mm between them and between hardware in the rows. Under the fastener heads, a countersink is first performed to 1/4 of the thickness of the sheet material.

Fastening plywood with dowels and nails.

Less commonly used are self-tapping screws with a wide head and dowels without a flange at the top. This option is cheaper, but the labor intensity of the work increases.

The parallelism of the outer edge of all other slabs in the same row is controlled by the 2 - 3 m rule.

The heads of the self-tapping screws are recessed into the countersunk holes with a special punch.

Recessing nail heads into plywood.

Then the entire area of ​​the room is filled with pieces of plywood of the same thickness using the same technology. The technique is described in more detail in the video below:

Putty of self-tapping screw heads

To smooth the base layer for laying block parquet, wood putty is used.

Two-component epoxy compounds are not economically viable for these purposes. And gypsum plaster and putty mixtures on wood are not used, in principle, as they conflict and are destroyed after just a week of use. You can mix small sawdust with PVA glue yourself to solve this problem.

Only the heads of the dowels and nails are sealed with putty, but not the longitudinal-transverse seams between the plywood slabs.

Sealing seams

On the one hand, the seams act as a compensation gap. That is, they cannot be filled with hard material - grouts, putties. On the other hand, leaving them empty is also a wrong decision. Since they will appear under the linoleum, after a couple of months, an uneven subfloor will cause accelerated wear of the carpet, laminate, and parquet.

Taking into account the seam spacing of 60 - 70 cm, the locks in the laminate will gradually break out, and individual planks in the parquet carpet will warp. Therefore, the seams are filled with inexpensive sealant. You can use a “liquid plug,” but this option costs at least two and a half times more.

Acrylic sealant for wood.

The cheapest is acrylic sealant, which is also considered the safest from the point of view of environmentalists. The composition is ideal for wood; it is usually used to seal the crowns of log houses. To reduce the consumption of sealant in the cracks, you can first lay a special cord for log houses.

You can use damper tape or sealant around the perimeter of the walls. In the first case, the tape must be secured to the walls before laying the first sheet.

Technology of fastening plywood with glue

Before laying plywood on a concrete base, we check its moisture level. Wood materials cannot be laid on a wet base. See this video for all the details of the process:

Related article: Repairing the blind area around the house with your own hands: how to repair it yourself

Method for determining screed dryness:

1. We cover the area of ​​the screed with polyethylene, press its edges to the surface, press down with heavy objects or fix it around the perimeter with tape.
2. If after 5 days the film remains dry, you can safely proceed to laying the plywood.

If condensation forms, wait for the screed to dry; the residual humidity should be no more than 2%.

Material cutting

It is convenient to mount pieces measuring 500 by 500 mm

The material is sold in large sheets; if they are laid in one piece, this can lead to deformation of the floor during operation.

We cut the plywood sheets into 4 squares ranging in size from 500 to 750 mm in width and length.

We cut the material using an electric jigsaw or grinder.

We number the squares so as not to confuse their location during installation and sketch out a diagram of their layout.

Gluing plywood

Before installation work, you need to level and clean the base from dust and debris. Primer of the base surface helps reduce glue consumption and improve adhesion to the surface. As a primer, you can purchase a special mixture or dilute glue with water.

We divide the floor into four rectangles and find the center. Without using glue, we lay out the plywood on the floor from the center with the seams staggered. We leave a compensation gap of 1 - 1.5 cm along the perimeter of the walls and between the squares of plywood.

Installation steps:

1. We apply an adhesive composition 2 mm thick, which we will have time to cover with the material before the adhesive composition sets. Glue the plywood to the screed.
2. We lay out the material and, if necessary, additionally fix it with self-tapping screws.
3. After the glue has completely hardened, sand the surface of the plywood with sandpaper or a grinding machine. This allows you to eliminate burrs, cuts, and small differences in height.

We lay the plywood on the screed according to the diagram and numbering of the sheets. Sheets of material must lie for several days in the room in which they will be used.

If you lay the floor immediately after the material has been brought in from the street, the base may move, because... it will either pick up moisture from the room, or, conversely, dry out sharply.