Marmox Multiboard products protecting the building envelope

Marmox Fireboard

Aside from dampening our spirits, the past winter has proved to be one of the wettest on record and will have reminded construction industry specifiers of the protection that render finishes can offer against driving rain

Render coats can only be effective, however, if correctly applied over a suitable substrate and in a manner where the build-up plays its part in ensuring the outer envelope achieves all of its objectives under the Building Regulations, including continuity of thermal insulation and airtightness, as well as weather protection.

January this year saw Kent-based manufacturer Marmox introduce a highly versatile new fire-rated board into its already diverse product range, expanding on the proven performance of its well-established Multiboard insulation panels for both internal and external wall insulation (IWI/EWI) applications.

Marmox Fireboard

Marmox Adhesive Fix

The new Fireboard offering features a Stone Wool core, which shares the unique Marmox honeycomb surface structure with its XPS forerunner, to create an A1 non-combustible certified render-backer that is fully weatherproof.

It can further be used internally across walls or ceilings to take a plaster finish, while providing sound absorption properties, as well as thermal insulation. The 600mm x 1200mm Fireboards are available in thicknesses from 20mm, 50mm and 100 mm – with the polymer modified mortar honeycomb coating applied to both faces.

With a nominal density of 150 kg/m3 the boards’ core material offers a compressive strength of nine tonnes/m2 so will resist impact damage and as with its renowned older relation, Fireboard also reduces thermal bridging at up-stands and other junctions.

The marketing manager for Marmox, Grant Terry, commented: “The introduction of Fireboard into our range significantly enhances our offer to the construction industry, meaning we have an A1 non-combustible backer board for internal or external use, which can safely be installed across masonry as well as timber or steel framing systems.

“The Stone Wool boards are made of formed molten rock, meaning it is impossible for the fibres to absorb moisture, so they will not degrade no matter what weather they are exposed to.

“The thermal conductivity of 0.037 W/mK delivers very good thermal insulation, while the tiny air pockets within the microfibre structure of the Stone Wool serves to interrupt the pathway for sound transmission, which solid materials facilitate. We expect Fireboard to find applications in new build and refurbishment work within residential, commercial and other sectors.”

Marmox’s Multiboard

Marmox Stud Frame Fix

While Marmox’s Multiboard has proved very popular down the years, with interior designers due to its versatility for fitting out bathrooms and even dog grooming parlours, it is equally well regarded by general builders and housing developers for its robustness when incorporated into exterior walling situations.

With its XPS or extruded polystyrene core, Marmox Multiboard is available in a wide range of thicknesses, enabling it to be utilised in a variety of applications, including as part of flooring build-ups, behind insulated rendering and – employing a taper version – even for self-draining balconies and promenade decks.

Marmox Multiboards deliver a range of positive physical characteristics, which make them ideal for refurbishment as well as new build situations, aiding energy efficiency and combatting condensation where warm moist air is present. The polymer modified concrete coating to both faces provides an ideal key for direct tiling, plastering or render applications. Meanwhile, the boards are both light to handle and easy to cut.

Importantly, past EWI projects have seen Multiboard used to carry either traditional sand and cement or lime renders and also as part of a proprietary specification where multiple coats of pre-batched silica renders are applied along with reinforcement mesh. Often employed on multi-storey residential and commercial projects, these renders can incorporate vivid colour pigments, which negate the need for further decoration, to guarantee a long low maintenance life.

The fact that both Fireboard and Multiboard are fully suited to refurbishment situations is of real benefit when it comes to maintaining the continuity or integrity of an elevation’s thermal performance.

This could be of particular importance where the specifier is seeking to upgrade solid wall constructions that cannot receive cavity wall insulation. This nowadays often sees replacement windows being installed on brackets, which set them outside of the original wall line – but still within a new ‘Outsulation’ zone – or requiring the old reveals to be thermally upgraded. In either case, Multiboard can provide a solution.

Cold bridging: The concept of thermal bridging or cold bridging has become of increasing importance in recent years as the Building Regulations Part L have been tightened, while SAP calculations can invoke punishing default values for the use of materials that have not been thermally modelled and this has led to increased use of a Marmox product, which is not only highly insulating but also able to offer excellent load-carrying capacity as part of masonry or other wall constructions.

Marmox Thermoblocks

Marmox Thermoblock

Marmox Thermoblocks are available in widths of 100mm, 140mm or 215mm and are formed from sections of XPS that encapsulates concrete mini-columns, these being attached at either end to the top and bottom layers of glass-fibre reinforced polymer concrete, to ensure a good bond with the rest of the structure.

As well as combatting cold bridging, where the inner leaf of masonry walls abuts the floor zone, Thermoblocks are also often utilised to support timber frame constructions or at vulnerable upper floor junctions, including beneath parapet walls.

As well as being widely adopted for low-rise residential building, Thermoblocks are also now being used for multi-storey modular buildings and for commercial projects, including leisure centres and around swimming pools.

Marmox can provide its customers with full specification guidance while, as detailed in a newly available, downloadable A5 technical brochure, Marmox Fireboard has been tested to prove compliance with BS EN 1182, EN 1716 and EN13823 (Resistance to fire test) by UKTC, along with other testing completed by the BRE.


Grant Terry

Marketing manager


Tel: 01634 835290


Please note: This is a commercial profile

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