Preparing Boarded Floors for Microcement

Here’s a step by step guide to preparing boarded floors for microcement. The process is exactly the same for all boarded floors: OSB, Plywood, Cement Board. Once the boards are well glued & screwed in place, you will need to apply epoxy, mesh & sand blind aka High performance Primer, scroll down for detailed instructions on that process too.

Applying High Performance Primer

Boarded floors are more susceptible to movement than any other sub floor. So the prep needs to be done carefully and we highly recommend using epoxy, mesh and sand blind – included in high performance kits & floor strengthening kit.t Board.

Well Consolidated
Make sure the boards are well glued and screwed in place to eliminate any chance of movement. Boards must be recommended as “floor grade” by the manufacturers. If you are fitting the boards yourself, use tongue & groove boards, with a suitable adhesive between the joins, leave to dry overnight and razor scrape/sand the excess off once set. Make sure silicone is not left on the surface to be microcemented. Products that you can use include: adhesive sealant or polyurethane wood glue. Countersink screw holes.

Completely Flat
Boards must be flush with one another, ridges will highlight in the microcement. Microcement can’t be used to level surfaces – it must be applied as thinly as the grain. The surface must be completely flat. As with all surfaces, microcement will follow the contours of the substrate it is going onto.

You have 2 options for achieving a flat surface:

Option 1: Filling the joins and screw holes with MicroDur Base or Wood Filler
This is the basic process – it relies on there being no movement at all in the sub-floor.
Fill the joins and screw holes with MicroDur Base or Wood Filler so that they are flush with the boards.

IMPORTANT: Leave until dry, minimum 24 hours. If the MicroDur Base/Wood Filler isn’t completely dry, the lines & holes may ghost through the microcement and be visible in the finish. Once the MicroDur Base/Wood Filler is dry, cut mesh and lay it over the whole area, not overlapped, flip the mesh so it curls towards the floor and apply neat Primer 100 over it with a medium pile roller. The Primer 100 will hold the mesh in place.

Option 2: Filling the Joins & Screw holes with Epoxy, Mesh & Sand Blind
This is the more advanced process, which we highly recommend for boarded floors where there is more chance of movement when compared to solid surfaces. These products are included in high performance kits & floor strengthening kit.

It can only be done on horizontal surfaces e.g. floors. Reduce the chance of movement transferring through to the surface by applying Epoxy, Mesh & Sand Blind over the entire floor. The epoxy will also fill the joins and screw holes to level off the floor. Use a trowel to apply an even coat of Epoxy over the sub-floor and mesh. You’ll need to ensure you have completely filled the joins and screw holes in the sub-floor and also completely covered the mesh, so that it has good adhesion with the floor.

Whilst the Epoxy is still wet, spread the quartz sand across the surface. You can scatter it by hand, starting at the entrance to the room and walking on the sand into the room. Or by walking on the Epoxy with spiked shoes. The following day, sand any high spots and hoover up all the loose sand.

Epoxy, mesh & sand are contained within the Floor Strengthening Kit available to buy from relentlessmicrocement.com.

You will need to prime the surface with Primer 100, you can apply a neat coat directly onto the sand. The Primer is applied with a medium pile roller.

NATURAL TIMBER FLOOR BOARDS will need to be over boarded with a timber composite like OSB/Plywood or Cemen