Laying plywood on a concrete floor: how to fasten (lay) under a laminate, without logs

Plywood installation is an essential step if you want to install laminate flooring over a concrete subfloor and guarantee a stable and smooth surface. Concrete floors require a different method than traditional wood subfloors, where you might use wooden joists (logs). Plywood serves as a base, leveling out any imperfections in the concrete and giving your laminate flooring a sturdy base.

It’s crucial to completely prepare the concrete surface before starting. To begin, sweep the floor to get rid of any dirt, dust, or grease. Fill in any holes or cracks in the concrete with an appropriate patching compound. Per the manufacturer’s instructions, let the compound dry completely. Making this preliminary preparation guarantees that your plywood will cover the concrete securely and flatly.

Next, pick the appropriate kind of plywood for the task. It is advised to use exterior-grade plywood since it can tolerate the frequent changes in temperature and humidity found in indoor spaces and is more moisture resistant. Although 1/4 inch to 1/2 inch thick plywood is usually sufficient for laminate flooring, the thickness of the plywood usually varies.

After measuring the space, cut the plywood sheets to size. Staggering the plywood seams from row to row will improve the subfloor’s structural integrity. Over the prepared concrete floor, place the plywood sheets, allowing a small space to expand around the room’s edges. Use an adhesive that is suggested and made specifically for this use to attach the plywood sheets to the concrete. Adhere uniformly, following the manufacturer’s instructions.

Give the adhesive enough time to fully cure after the plywood sheets are firmly positioned and adhered to the concrete. A solid connection between the plywood and the concrete subfloor is ensured by this curing procedure. Examine the entire plywood surface for any gaps or loose edges after the adhesive has dried. Sand down any sharp edges and use wood filler to fill in any small gaps to create a smooth, level surface that is ready for the installation of laminate flooring.

You can successfully install plywood on a concrete floor to provide a sturdy foundation for laminate flooring by following these instructions. This approach offers a workable solution that guarantees the longevity and durability of your laminate flooring installation by doing away with the need for conventional wooden joists, or logs.

Method Steps
1. Preparation Clean and dry the concrete floor thoroughly.
2. Moisture Barrier Install a moisture barrier to protect the plywood from moisture in the concrete.
3. Lay Plywood Place the plywood sheets on the floor, ensuring they fit tightly together.
4. Fastening Secure the plywood to the concrete using concrete screws or adhesive, ensuring a flat surface.
5. Underlayment Install an underlayment over the plywood before laying the laminate flooring.

Advantages and disadvantages

Like any material, plywood has advantages and disadvantages. Therefore, selecting the appropriate material and applying it correctly are essential to providing a high-quality and long-lasting layer beneath laminate and linoleum.

  • If you plan to install electrical wires under the floor, plywood is highly flammable and can cause a fire at the slightest short circuit.
  • In production areas where there are vibrations (working machines, for example), it is forbidden to lay plywood on logs, since vibrations will quickly destroy the material and the floor will soon require repair.
  • In old buildings where frequent and strong temperature/humidity changes are noted.
  • In areas where water supply pipes are laid under the floor.

Plywood can be laid on a concrete screed in all other situations, and it can solve many issues and offer benefits.

  • Environmental friendliness and safety for health, human life, absence of any toxic fumes, harmful substances.
  • High level of strength and ability to perceive, distribute loads.
  • Low cost.
  • Simplicity and ease of work – laying plywood on a concrete floor is not difficult, as well as cutting, fitting.
  • Wear resistance, reliability and durability.
  • Minimum weight, which is important in cases where it is forbidden to give additional load to the foundation, ceilings.
  • Small thickness of the material, flexibility.
  • Plywood acts as an additional layer of sound / heat insulation.

It is important to note some of the drawbacks of plywood, including the fact that its basic varieties cannot be used in rooms with high humidity (only sheets labeled with FSF, which are much more expensive), and that the surface must be aligned with excessively large skates.

You must ascertain the base’s relative humidity before affixing plywood to a concrete surface. If it’s high, you should apply a waterproofing layer or coat the concrete with a primer that offers protection and deep penetration.

How to choose the right plywood

Selecting the appropriate plywood material is crucial, regardless of whether it is intended to be installed on a concrete floor with or without logs. For the sheets to be appropriate for this kind of work, they need to possess specific qualities and be of excellent quality.

– marked plywood About 10 mg of E1 and 10–30 mg of E2 are present per 100 g of material. Select E1 for residential properties.

Therefore, plywood with a thickness of 12–16 millimeters and grades FK and E1 of the second grade—of which there are four quality groups—is the best choice. The materials in the first group have the fewest defects possible; the materials in the second group may have veneer inserts or knots; and the sheets in the third group have a lot of cracks, knots, and other defects.

Although the fourth group of plywood exhibits the necessary strength indicators and is therefore utilized in construction, it is unsuitable for use beneath laminate on a concrete floor. Interior work is not done at all with this group.

The second group’s plywood is the best choice for laying on a concrete floor because it offers the best value in terms of both quality and price. If the first option isn’t suitable, you can select a different plywood that meets your budget and needs.

Although the above plywood option is the best choice for laying on a concrete floor, the master can select another type of material from the list.

Cutting and fitting plywood

After deciding which plywood is best for the job, you must purchase the quantity of sheets needed, which is determined by multiplying the floor area by five to ten percent, plus inventory. A typical plywood sheet measures 1.25 by 1.25 meters. Working with squares isn’t always convenient, so you’ll need to carefully cut the plywood to precisely fit the floor before securing it to the concrete.

Skilled artisans suggest cutting plywood sheets into four 60 by 60 centimeter squares. This will produce the necessary amount of damper seams, which are intended to offset any potential deformations of the material caused by changes in temperature and humidity. The elements deform less the smaller they are in size.

For the best results, use an electric jigsaw to cut plywood as this will prevent delamination and chipping. Without the use of glue or screws, the cut sheets are arranged on the base for initial adjustment. In this manner, the components precisely align with the floor’s layout, accounting for all protrusions, niches, and features.

Seams between the squares should be 8–10 mm thick, and there should be at least 15–20 mm of space between the walls and the sheet’s outer elements. To ensure that none of the four seams cross at one location, it is best to arrange the sheets with an offset, such as brickwork.

Once the sheets are positioned on the floor, you should take a picture or draw a diagram showing where they are so that you don’t have to waste time on this step later on when laying.

Methods for attaching plywood to the base

It is advisable to allow for two different methods of fastening when laying plywood on a concrete floor: glue and self-tapping screws. The thickness of the sheets is typically taken into consideration when choosing self-tapping screws, though there are variations in adhesive types.

The lack of a strong smell and safety for human health and the environment are two benefits of water-based adhesives. The drawback is a lengthy (many days) period of complete drying, which slows down the process by causing work stoppage.

Although a solvent-based adhesive dries considerably quicker, the surrounding area is literally filled with an offensive, strong smell. Ventilating the room is necessary to get rid of the smell, but doing so might damage the finish.

A two-component adhesive is the best option for attaching plywood beneath laminate or linoleum. The mixture dries fast and doesn’t have an unpleasant smell. The glue’s characteristics allow it to function well even on partially dry concrete screed.

To ensure a successful laminate installation, there are several important steps to take when laying plywood over a concrete floor. It’s imperative to properly clean and prep the concrete surface first. To make a level and smooth surface for the plywood, clear away any dust, debris, or old adhesives.

Next, pick the appropriate plywood type and thickness. Plywood that is between 1/4 and 1/2 inch thick is usually appropriate for this use. Make sure the plywood panels are cut to match the room’s measurements, leaving as little space between the sheets as possible.

When your plywood is ready, use a high-quality adhesive made specifically for use with wood and concrete. Using a trowel or other appropriate tool, evenly apply the adhesive to the plywood panels’ backside, making sure to ensure good coverage.

Each plywood panel should be carefully placed onto the prepared concrete floor after the adhesive has been applied. To guarantee that the plywood makes good contact with the concrete surface, apply pressure. To temporarily hold the plywood in place while the adhesive sets, you can use weights or clamps.

Lastly, before installing your laminate flooring, let the adhesive cure in accordance with the manufacturer’s instructions. For the plywood and concrete to form a solid bond and provide a sturdy foundation for your laminate floor, this curing period is essential.

You can successfully lay plywood on a concrete floor without the need for additional support, such as wooden logs, if you carefully follow these steps. This technique not only makes installation easier, but it also guarantees a level surface, which extends the life and functionality of your laminate flooring.

In order to achieve a stable and long-lasting finish, careful preparation and the right fastening techniques are needed when laying plywood on a concrete floor beneath laminate without the need for sleepers. You can build a smooth and sturdy base for laminate flooring by selecting the proper plywood thickness and quality, making sure the concrete is clean and level, and using the appropriate adhesive or mechanical fasteners. This post walks you through the process step-by-step and provides helpful advice and solutions to get a polished finish without the need for sleepers or other extra structural support.

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Dmitry Sokolov

Chief engineer in a large construction company. I have extensive experience in managing construction projects and implementing modern technologies.

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