FAQ – What Is Marmox & How To Use Marmox
  • What is Marmox?

    Marmox is a construction board made of extruded polystyrene, which is totally waterproof (when water is not under high pressure), faced on either side with a fibreglass mesh, which is embedded into a thin cement polymer mortar.

  • What are its benefits?

    Marmox is lightweight, easy to work with and can be cut with a hand saw or knife. Marmox is non-toxic, will not rot or absorb moisture and has excellent insulation properties.

  • Why do I need Marmox?

    Marmox will save you money by acting as a very efficient insulation barrier. It reflects the heat upwards into the floor tile instead of allowing the heat to warm up the concrete slab below.

    By using Marmox you will find that after switching on your heating, your floor tiles will warm up in about 10-15 minutes. Without Marmox it could take anything from 2-3 hours or more.

  • Is Marmox suitable as a tile backer?

    Yes, Marmox is designed as a tile backer with the added advantage of being an insulation board as well and can withstand 40 tonnes per sqm when tiled over.

  • Can I tile onto the boards or do I have to prime them?

    No, the Marmox material is ready to tile, you do not need to do anything to it.

  • Can I put the boards directly onto floor joists?

    No, although the boards can take a weight of over 40 tonnes over per square metre, they can be distorted by the point load pressure of sitting on a joist.

  • Where else could I use Marmox?

    Marmox can be used on walls, ceilings and floors in bathrooms, kitchens, garages, lofts and conservatories to name a few.

  • How do I cut Marmox?

    Use a Stanley knife.

  • How do I join Marmox boards together?

    On floors, you butt them up laid in a staggered fashion just the way a brick wall is built.

  • What adhesive should I use to fix Marmox?

    It is recommended that a flexible cementitious floor tile adhesive be used. Solvent based adhesives must NOT be used as these could cause damage to the Marmox boards.

  • How do I waterproof the joints?

    By laying a bead of polyurethane sealant along the edge of each board. When the adjacent board is butted up, the joint is made instantly waterproof.

  • Can the boards be placed above underfloor heating?

    No, the boards are insulation boards therefore they should go below the heating elements otherwise they will block the heat.

  • How does Marmox compare to plasterboard?

    There is no comparison. Standard plasterboard offers approximately 1/6th the µ value of an equal thickness of Marmox and yet is approximately 7 times heavier. When used in wet areas such as bathrooms or showers, Marmox is totally waterproof whereas plasterboard will absorb water unless it is of the waterproof variety which will cost considerably more.

    • Marmox is 1/7th the weight of plasterboard
    • Marmox is waterproof whereas ordinary plasterboard is not
    • Marmox (10mm) has a µ value of 2.7 whereas the µ value of 12.5mm plasterboard is 12.8 W/M2 K (the lower the µ value the better the insulation).