Frequently Asked Questions
Regarding Marmox boards (now known as Marmox Multiboards)...
1) Which way up do the boards go?
It does not matter; both sides of the board are the same.
2) Is one side of the board waterproof?
No, unlike some other boards, it is the core of the board itself that is waterproof.
3) Can I tile onto the boards or do I have to prime them?
The Marmox material is ready to tile; you do not need to do anything to it.
4) How many boards do I need?
Small boards are 0.6m x 1.25m that’s three quarters of a square metre so you need to divide the area you want by three quarters and that’s the number of ‘short boards’ you require.
5) 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.
6) What adhesive should be used?
Use tile adhesive; the powder version rather than pre-mixed version. So that it’s the correct strength for the tiles, this will usually be the same product you will be using to fix the tiles with.
Normal tile adhesive (C1 type) can be used on walls for light to medium weight tiles and for plastering but for heavier tiles, for external use, on floors and in wet areas a ‘flexible’ version should be used; this is categorised as “C2” (or C2F) type.
7) Can plasterboard dot and dab adhesive be use?
No, plasterboard adhesive is gypsum based, Marmox boards have a cementitious skin therefore a cement based adhesive is needed.
8) Besides tile adhesive, can other adhesives be used?
Solvent free versions of mastics such as ‘No More Nails,’ ‘Bostik Serious Stuff’ etc will work.
9) How do I stick Parquet flooring to Marmox?
Only non-solvent, non-water based adhesives (such as BAL Stopgap)can be used. This is because Parquet flooring is usually stuck down with solvent based adhesive which must not be used with Marmox and Marmox is usually stuck down with a water based tile adhesive which must not be used with Parquet flooring.
10) What thickness board is sufficient to make a difference to heat loss?
To meet current building regulations very thick layers are required (phone us to calculate this if necessary) however, if at least a 20mm thick Marmox multiboard is used to insulate a wall it will make a noticeable reduction to the heat loss.
11) How many washers are needed?
Without using any adhesive, a short board will need two rows of five (10) or if the board is 12.5mm or 10mm thick, three rows of four (12). A long board will require 15 fixings; three rows of five.
Used with adhesive (the dot and dab method), five fixings per short board and nine fixings per long are recommended.
On floors, tile adhesive method should be used whenever possible. If the only practical option is mechanical fixing, screws and washers should be used every 30cm – that is 15 per short board.
12) Can I apply a plaster finish to the Marmox boards?
Yes, but first, prime the board with either dilute PVA or SBR and skim coat with plaster whilst the board is still tacky.
13) 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.
Regarding Marmox Showerlays...
1) Can Showerlays be cut?
Yes, because the slope is constant from the outside to the drain, even after cutting off 10 or 20cm from one of the sides, the remaining surface will still be sloping.
2) Is a Showerlay waterproof?
Like Marmox Multiboard, the Showerlay has a core of extruded polystyrene. It is impossible for moisture to pass through this. The drain frame is fitted in the factory which also guarantees that water will not be able to pass through this product. The only places water can penetrate is at the edges where the Showerlay meets the wall or the rest of the floor – these joints must be waterproofed with waterproof tape or similar.
3) Does the Showerlay need a waterproof membrane or waterproofing primer?
No, the material is 100% waterproof however, membranes and primers are sometimes useful in covering the joints and if they cover the Showerlay they will do no harm.
4) Can Showerlay be used on concrete floors?
Yes, the Showerlay can be used either concrete floors or wooden floors.
5) Can mosaics be used on Showerlay?
Our instructions say that that tiles smaller than 5cm x 5cm should not be used, this is because very small mosaic tiles do not spread the load and if for example, a step ladder, a wheelchair or a bath stool press onto a mosaic the point load could distort the showerlay underneath. However, for light domestic use only, small mosaic tiles can be used.
6) Can non-tile surfaces such as vinyl be used?
No, the drains (point drain and linear) are designed for use with a tiled finish only.
7) Can a Showerlay be placed on joists?
No, the normal Showerlay cannot sit directly on joists. It must be supported underneath by a flat surface.
8) What adhesive should be used?
Use a powder based ‘flexible’ tile adhesive; these are categorised as C2 or C2F. Alternatively, Showerlays can be fitted using non-solvent grip adhesives such as ‘No More Nails,’ ‘Bostik Serious Stuff’ etc.