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Installing concrete slabs – how do I prepare the surface?

Architectural concrete in the form of ready-to-install panels is a practical and effective way to frame interior walls and exterior facades, stairs, fireplaces and floors. In order for decorative concrete slabs to be laid successfully, the surface must be properly prepared.

Suitable surface texture
The adhesive surface of architectural concrete panels must be porous to ensure good stability and adhesion. It is worth paying attention to this during the construction phase and not using gypsum plaster or any other smooth surface at this point, as such a surface can cause the board to peel off.

Preparation of the substrate for panel mounting:
Step one – cleaning the surface
The first step in preparing the surface for concrete slabs is to clean the bonding surface of any contamination, such as loose mortar, dust or lumps, as well as any paint or glue residue. If the panels are glued to gypsum plaster, the substrate should be properly prepared by cutting the wall at the points where the adhesive meets the wall (to bond the adhesive under the gypsum plaster to the substrate) or mounting, without affecting the subsurface through the use of mechanical fasteners.

Step two – priming the substrate
The next step is priming with the selected primer. For the proper installation of concrete slabs, a properly primed substrate is necessary as it increases the adhesion and durability of the substrate, thus ensuring safe installation and the desired adhesion quality.

It is recommended to prime the back of the panel (the surface glued to the wall) with an ordinary primer and the wall itself with an adhesive primer with an admixture of quartz sand 24 hours before installation.

After priming, allow the surface to dry completely. Only then can concrete slabs be applied to the prepared surface.

Substrate for differently laid panels
Typically, concrete slabs for walls are attached by gluing. Before gluing, check that the glue does not damage the board, i.e. H. Glue the board and wait for the glue to dry to check for any discoloration or damage.
Follow the adhesive manufacturer’s recommendations.

We recommend mounting with polymer glue (waterless). The glue should be applied using a gun for squeezing thick masses in parallel vertical strips every 20-25 cm. The panels should be laid with a joint (expansion) of at least 3-5 mm.

Assembly is also possible using screws with washers, dowels or combined methods. The choice of laying method is tailored individually to the given surface and the height at which the panels are to be laid.

If you decide to install the panels with screws, after priming the surface, you should also drill holes for expansion dowels in the previously marked places, then attach the expansion dowels and tighten the screws. When we lay architectural concrete slabs with anchors, holes should be drilled in the floor and slabs at the appropriate locations and the anchors should be placed. MK Concrete provides anchor hole drilling services. Check out our offer.

What are the best substrates for decorative concrete?

The absolute requirements for the substrate for concrete slabs are dryness and stability. Architectural concrete is a universal material that harmonizes with other building surfaces, including: raw concrete or plaster. An exception is gypsum plaster, which is highly hygroscopic and therefore does not meet the stability requirement. In this case, instead of chipping gypsum plaster, it is worth installing an OSB board (Directed Flat Strand Board), MFP board or gypsum plasterboard with increased moisture resistance.

The best substrates for decorative concrete panels are: concrete, terrazzo, lime-cement plaster, OSB boards of category III or IV and plasterboard with increased moisture resistance.