Marmox Thermoblock (65mm)
  • Marmox Thermoblock (65mm)
  • Marmox Thermoblock (65mm)
  • Marmox Thermoblock (65mm)
  • Marmox Thermoblock (65mm)
  • Marmox Thermoblock (65mm)

Marmox Thermoblock (65mm)

Tax included

Marmox Thermoblocks. The solution to Thermal Bridging at the wall/floor junction. Also for use at the tops of walls, beneath parapet walls and under door thresholds.


More on Marmox Thermoblock (65mm)

  • Description
  • General information
  • Specification Data
  • Downloads


According to BRE, “Thermal bridging can be responsible for up to 30% of a dwelling’s heat loss”.

So, what is a thermal bridge? Often referred to as a cold bridge, thermal bridging occurs in areas of a building that have higher heat transfer than the materials that surround it. Whether that be because there isn’t much insulation or because there is a break in the insulation. One area that has always been a problem is where the wall meets the floor. This is because insulation is generally not load-bearing and so insulating under bricks or blocks is an obvious problem.

What are Marmox Thermoblocks?

Load-bearing, insulating, building blocks, designed to be placed at the base of masonry or timber/metal frame walls to prevent heat loss through the bottom of walls. By simply replacing one layer of standard building blocks with Thermoblocks and then sealing the joints with Marmox MSP360 Adhesive & Sealant, Marmox Thermoblocks will help to eliminate thermal bridging!


High thermal insulation

Proven as a highly effective form of insulation, extruded polystyrene is an ideal material for Marmox Thermoblocks and allows them to perform with a thermal conductivity of 0.05W/mK. This will offer a significant reduction in ‘y’ values when used at wall to floor junctions.

High compressive strength

Cold bridges typically occur where the wall meets the floor. Now, historically there wasn't a solution for placing insulation under a supporting wall and the reason for this was because the weight of the wall would have crushed the insulation. However, with Marmox Thermoblocks ultra high strength design, this problem can be a thing of the past.

They are strong enough to withstand a load of 9 newtons (9N/mm2), which in some cases, means they will be even stronger than the concrete blocks they are replacing.


Being made using an extruded polystyrene, which is closed cell, Thermoblocks are completely impermeable to water. This means they can be used in damp conditions without any loss of their insulating properties. So, not only do Marmox Thermoblocks reduce thermal bridging but they also create a moisture barrier.

Guaranteed Compliance to Building Regulations

All building regulations in the UK and Ireland say: “The building fabric should be continuous over the whole building envelope and constructed so that there are no reasonably avoidable thermal bridges in the insulation layers caused by gaps in the various elements.”

Marmox Thermoblock satisfies this requirement perfectly by bridging that gap between wall insulation with the floor insulation. They will guarantee compliance with current regulations and with proposed zero carbon regulations.


NOT an Aircreate thermal block

Marmox Thermoblock should definitely not be mistaken with an Aircrete thermal block. In fact, they would typically replace the bottom row of Aircrete blocks to stop the cold bridge at the critical wall/floor junction.

BRE Third Party Accredited Junction Details - Thermal Models

The performance of Marmox Thermoblock in several common wall/floor junction details has been independently assessed and certified by the BRE. The BRE scheme offers an on-line database of independently assessed and certified thermal junction details which can be used in the SAP/SBEM energy assessment of the building to ensure it meets the appropriate UK and Irish building standard requirements. Using these results will save architects and designers both time and money because they will not need to have their designed modelled themselves.

Junctions incorporating the 100mm and 140mm wide block have been thermally modelled to provide a series of psi values and temperature factors (surface condensation factor fRSI) for two wall types:

With cavity walls: a)slab on ground, b) beam and block, c) suspended timber frame.

With timber frame construction: a) slab on ground, b) suspended timber frame.

Architects and Energy Assessors simply log onto BRE’s site and click the junction type required. BRE-Global is a UKAS accredited laboratory which gives confidence and assurance to designers that using Thermoblock thermal insulation in the common positions that have been modelled can guarantee compliance to the appropriate building standards. The full report with the results and thermal model drawings is given below in the "Datasheets" section.

Marmox – Modelling analysis

In addition to the BRE accredited designs, we can offer a limited and basic thermal modelling analysis of your specific junction type. Ψ  

General information

  • Ultra-High Strength (9 Newtons)
  • Low Thermal Conductivity
  • Guaranteed Low Ψ Values
  • Fully Waterproof
  • Easy to Handle onsite
  • Easy to Cut

Specification Data


Marmox Thermoblock



All the Marmox Thermoblocks are 600mm long and are available in either 100mm, 140mm or 216mm widths.

Standard Thermoblock - 65mm, which is the same height as a brick.

Extra Thick Thermoblocks - 100mm, thick which offers even greater insulation.



Marmox Thermoblocks are made using extruded polystyrene, which is then coated on the top and bottom with fibreglass mesh which is embedded in a cement polymer mortar, which allows for a good adhesion to the surrounding material. Throughout the 600mm long Thermoblocks are 12 (2 rows of 6) epoxy polymer concrete columns, which is what gives Marmox Thermoblocks such a high compressive strength.


Download the Full Specification Sheet HERE


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