Stabilization of the underlay during floor renovation – durability and quality of finish

When planning a floor refurbishment, underlay stabilization is a special consideration, especially for old plank floors, which are often characterized by sagging and squeaking when walked on. An incorrectly prepared underlayment can lead to undesirable effects, such as creaking of the new floor or cracks in the laid ceramic tiles.

The reasons for the creaking of plank floors can be various. Often it is enough to replace or reposition a loose board, and in the case of its deformation – to use a new board with appropriate parameters.

Important factors that contribute to the creaking of plank floors include:

  • Laying boards that are too wide (more than 15 cm), which are more susceptible to deformation and bending.
  • Use of boards of insufficient thickness – the recommended thickness is 38 mm (1 ½ inch), however, for economic reasons, 25 mm (1 inch) boards are often used.
  • Arrange the boards so that the core side faces downwards. This causes the edges of the board to lift as it dries and the nail joints to loosen. In order to avoid this problem, it is recommended to lay the boards with the core side up, however, then the middle of the boards may form protuberances on which traces of use are more easily visible. It is also common to arrange the boards alternately, once with the core side down and once up.
foundation stabilization

If the replacement of the boards turns out to be insufficient or we plan to lay ceramic tiles, it is necessary to stabilize and stiffen the floor made of boards. For this purpose, you can use:

  • Double-layer OSB boards with a total thickness of min. 25 mm, laid with offset joints.
  • Gypsum fiber boards, laid in a similar way as OSB, or boards with milled edges.
  • A layer of special screed with a thickness of min. 3 cm reinforced with mesh. In some cases, experienced contractors also use thinner layers of their own compositions, based on tile adhesive.

In the case of laying ceramic tiles, it is recommended to use a flexible adhesive dedicated to “difficult substrates”. In damp rooms, it is also necessary to use damp insulation, because the tiles themselves do not ensure full tightness. The best solution is seamless insulation with the so-called “liquid film”, applied in at least two layers. It is also possible to use a special tile adhesive that acts as insulation.


When replacing an old hardwood floor that has been laid over joists, be careful not to block the ventilation openings. Adequate ventilation is essential to ensure proper use of the floor and to avoid rising humidity and rotting of the floor. Stabilizing the underlay during floor refurbishment is a key step in ensuring the durability and quality of the finish. Before deciding to renovate the floor, we recommend consulting experienced professionals. They have the knowledge and skills in the proper preparation of the base and the selection of materials optimal for a specific case.

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