Micro Joints – the discreet new way to protect tiles installed over underfloor heating systems

The popularity of underfloor heating systems has increased significantly in recent years, as they provide a cost-effective, comfortable, unobtrusive heating solution for millions of homes. However, these systems often cause movement between the subfloor and the floor finish in the form of expansions and contractions. Failing to accommodate for this movement will almost certainly result in cracked tiling surfaces.

Dural UK are proud to have developed a solution in the form of Micro Joint Infill, which provides discreet stress protection for tiles and natural stone on heated floors.

Underfloor heating systems and the potential problems they bring

Over the past five years, there has been a sharp rise in popularity in underfloor heating systems, with industry experts even estimating the market nearly doubling annually since 2014. It is easy to understand the reasons for this surge in popularity.

For homeowners, installing underfloor heating systems brings high comfort levels and low running costs (upto 30% greater energy efficiency compared to traditional heating methods). For Architects and Designers, incorporating underfloor heating systems into residential build projects enables them to achieve modern energy effiency regulations, reduce the carbon footprint of buildings, and facilitates more contemporary design concepts.

However, underfloor heating systems can often prove to be problematic for tiled flooring installations. The main problem with underfloor heating systems is the resultant movement, or thermal expansion, it causes in the subfloor. The movement is then transferred into the surface layer – the tiled flooring. But as the surface layer expands and contracts at different rates to that of the subfloor beneath it, this results in tensions and stresses too great for the tiled flooring to cope with.

There are two main outcomes to this – one is the tiles could ‘tent’ or ‘pop’ off the floor resulting in loose tiles, and the other is hairline cracks could appear in the tiled surface. This is particularly common in large format tiles which are experiencing huge growth levels and are expected to be a big flooring trend in 2016. Large format tiles have a higher coefficient of thermal expansion, so for a given temperature rise they will grow proportionally more than smaller tiles. If this rate of expansion isn’t accommodated for, the tile material will crack or ‘tent’ under the pressure.

Benefits of Micro Joint Infill for tiles on underfloor heating systems

UK Building Regulations, in particular BS5385, stipulate that expanses of hard flooring as a finished surface material have to conform to various aesthetic and functional standards. To achieve compliance, it is essential for 40sqm or above flooring installations to have some sort of movement protection in place, to absorb movement being transferred between substrates thus protecting the surface tiles.


Micro Joint Infill has been specially developed for tiled flooring installations which are laid over underfloor heating systems, particularly for residential developments. It provides effective movement protection for tiles and natural stone on heated floors. It means a tiled flooring installation with Micro Joint Infill used is able to effectively absorb the movement energy transferred from the subfloor, protecting the tiles from cracking and loosening.

Importantly, it can be colour matched to the existing grout or tile colour for a discreet appearance – in fact any colour in the RAL chart. This favours tiled flooring installations where the homeowner is adiment tradtional movement joints too obtrusive and spoiling the aesthetics of the seamless design. Surface movement Joints have to be positioned over existing joints in the subfloor construction, and if these hadn’t been considered at an early design stage it meant the surface movement joints could potentially run through the middle of a tiled floor ruining the intricate flooring design.

The Micro Joint Infill is simply applied into the grout line spaces in between tiles and can be used on Brick Bond or Opus floor tile layouts. Due to the colour matched nature of the Micro Joint Infill it helps to create a beautiful, seamless design to the tiled flooring.

Micro Joint Infill is supplied in a kit format, and comprises of Part One Base, Part Two Hardener, Cartridge assembly and protective gloves. Part Two is simply mixed with Part One thoroughly until a consistent colour is achieved. This is then transferred into the cartridge and is then applied into the grout lines within the tiled floor installation. After application, the Micro Joint Infill will cure over a period of approximately four hours and has a 45 Shore A hardness rating.


Architects and Designers will benefit from incorporating Micro Joint Infill into their build projects, as it means they will have confidence in designing seamless tiled flooring over underfloor heating systems. The Micro Joint Infill can be colour matched to the grout or tile colour therefore causing minimum disruption to the visible surface. It is important to note Micro Joint Infill must not be used as a substitute for intermediate movement joints over subfloor movement joints, which will still need careful consideration in the early design stages. Importantly, the Micro Joint Infill will ensure tiled flooring installations are fit for purpose and exceed requirements BS5385 for hard flooring applications.

Micro Joint Infill will benefit Installers and Tile Fitters as it is a cost-effective solution to achieving a beautiful tiled flooring with minimal chances of cracking or loosening (if good tiling practices and procedures are followed, refer to The Tile Association for more information). It is easily applied with minimum wastage (depending on care of application) and offers excellent protection from thermal expansion caused by underfloor heating systems.

Matched accurately to the grout, tile or any colour in the RAL range, Micro Joint Infill effectively blends into the floor surface whilst providing the required stress relief modern heated floors require for a long lasting beautiful performance.

For more information on Dural Micro Joint Infill please contact our flooring experts on telephone 01924 360 110.

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