Frequently asked questions

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1. 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.

2. What are its benefits?

Being extremely strong, Marmox can be used as a structural element in the floor. It will not only take a load of 30 tonnes per square metre (at 10% deflection), so it's ideal for putting under your floor, but it keeps your floor warmer, longer, by not allowing heat to penetrate down into the concrete substrate below.

3. Why do I need Marmox?

Because 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.

4. How can you prove this?

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. The benefit is self-evident.

5. What thickness Marmox do I need?

The thicker the Marmox the better the heat insulation, but obviously if you have an existing floor that you want to insulate, you may well be governed by the thickness you can add to the floor because of the height from the finished floor to the underside of your door. Even by using 6mm Marmox you will notice the benefit of insulating with Marmox.

6. How does Marmox compare to plasterboard?

It doesn’t’ there really is no comparison. Standard plasterboard offers approximately 1/6th the U 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 (when water is not under high pressure) whereas plasterboard will absorb water unless it is of the waterproof variety which will cost considerably more.

Compare a few characteristics of Marmox against plasterboard. Marmox is 1/7th the weight of Plasterboard. Marmox is waterproof (when water is not under high pressure), ordinary plasterboard is not. Marmox (10mm) has a U value of 2.7 against 12.8 W/M2 K of 12.5mm Plasterboard (the lower the U value, the better the insulation).

7. Where else could I use Marmox?

It can be used on walls, ceilings and floors in bathrooms, kitchens, garages, lofts, and conservatories to name a few. In fact the list is endless.

8. How do I cut Marmox?

Simply use a Stanley knife.

9. 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. On walls they can be butted up & mechanically fixed using plugs & screws.

10. How do I fix Marmox to walls?

Marmox can be either fixed to timber battens with screws and screw cups or fixed directly to brick or block walls by drilling, plugging and screwing the boards to the wall. If the wall is to be plaster finished, the joints should be reinforced with a plaster scrim.

11. How many fixings do I need to secure Marmox to the floor or wall?

In a Marmox panel 2.5m long, fifteen fixings equally spaced are required on the floor. On walls, fixings should be made into the timber studs or brickwork, as you would fix plasterboard. If adhesive is to be used either on the floor or the wall, boards should be fully bonded.

12. How many fixings do I need to secure Marmox to the ceiling?

For a Marmox panel 2.5m long, 15 fixings are required, 5 along either length & 5 down the middle.

13. How do I fix Marmox to concrete floors?

Lay a 5mm bed of cementitious flexible floor tile adhesive and lay the boards in a chequer plate fashion (like bonding brickwork) onto the adhesive. Firmly bed and allow the adhesive to set before allowing work to continue on the board surface - approximately 24 hours.

14. How do I fix Marmox to wooden floors?

If the floor is sound and level, Marmox boards can be mechanically fixed using screws With large heads, or washers under the head, to enable the screws to 'bite down' into the Marmox board. If the flooring is uneven, the floor should be levelled using plywood first, before fixing the Marmox to the floor.

15. 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.

16. How do I waterproof the joints?

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