The Thin-Joint System

Thin-Joint blockwork gives a faster, more airtight build which meets the definition for Modern Methods of Construction.

Thin-Joint is a Modern Method of Construction combining larger format Celcon Plus Blocks and Jumbo Blok ranges with Celfix, a specially developed Thin-Joint Mortar.

Designed to replace traditional sand:cement mortar, Celfix mortar is the key to the H+H Thin-Joint System. Celfix is cement-based and will result in mortar joints of just 2-3mm.

The main reason for specifying Thin-Joint is the speed of build. Traditional, 10mm mortar joints need to be given 24 hours to set before further loading can be applied. LABC guidelines suggest that no more than 1.5m height should be built in one day.

Celfix mortar, on the other hand, will start to set within 10 minutes, approaching full design strength in just one to two hours. This means that an entire storey-height can be completed in a single day if required.

The setting time of Celfix mortar is not affected by weather conditions, so building can continue at speed even during winter months.

Completing the envelope: fast

The loadbearing inner leaf can be completed independently of external brickwork, allowing the full weathertight envelope, including floors and roof, to be built quickly.  Interior follow-on trades can then start sooner, reducing the time for the overall build, often by several weeks.

Using the Thin-Joint system allows for construction times equivalent to off-site system-build solutions, without their associated lead times and the resulting cost-savings can be very attractive.

The system retains the flexibility of design that a traditional build enjoys, allowing adaptations on site for any issues that may have been overlooked at the design stage. It also simplifies any changes that are made to the building at a later date, such as extensions, conversions or conservatories.

High performance buildings

Using the dimensionally accurate blocks with a very thin mortar joint gives an exceptionally accurate wall build that provides very high levels of thermal insulation, airtightness and acoustic control.

Air-tightness is now an integral part of achieving Building Regulations compliance and has become an important factor in the design and construction of any building.

Preventing warm air from escaping through uncontrolled ventilation and air leakage is a key component in controlling heat loss through the fabric of a building.

Tests undertaken by Building Services Research and Information Association (BSRIA) have shown that H+H aircrete achieved an air permeability of 0.12m3/hr/m3 measured at 50 Pascals. A Thin-Joint wall structure (with fully filled joints without finish) gives an air tightness performance of around 1m3/hr/m2.

The overall air leakage of a building is very much dependent on the external fabric performance as a whole. It relies on good workmanship and detailing at junctions and service penetrations. Values of less than 5m3/hr/m2 have been regularly achieved with these systems.

The exceptional air-tightness is one reason why Thin-Joint is frequently specified for buildings being completed to Passivhaus standards.

Combined with the thermal insulation inherent with aircrete as a material, a Thin-Joint wall will meet the most exacting thermal and acoustic performance requirements. These will be considerably in advance of the Future Homes Standard and current Building Regulations.

A full set of U-Value calculations for a range of Thin-Joint wall constructions with various insulation options can be downloaded here.

The preferred method of wall construction throughout most of Europe, this innovative and award-winning system is now firmly established within the UK.  The Thin-Joint system can be used for both residential and commercial projects.

The Thin-Joint system can be used for interior and exterior walls (cavity walls or solid build) and is suitable for both residential and commercial projects – it fits within the government definition of Modern Methods of Construction  MMC Category 6.