Thomas Armstrong - Information Zone

Thin Joint Construction

Thin Joint Construction

What is Thin Joint Construction?

Thin Joint construction is a masonry wall construction technique which replaces conventional 10mm cement:sand mortar joints with 2-3mm joints using a special adhesive mortar. This technique of 'gluing' blocks together results in a significantly faster build build time, less waste, less materials and plant required on site and walls with improved u-values and air-tightness.

This technique of construction is growing in popularity in the UK and already accounts for up to 90% of masonry construction in many European countries! Furthermore, as building regulations are updated and the technical and environmental requirements of buildings are ever-increased, the benefits of this quick, easy and highly effective building method will become more and more apparent. In effect,Thin Joint construction offers a solution to builders wishing to maximise the thermal performance of a building, minimise CO2 emmissions over the building's lifetime and yet maintain the familiarity, comfort, stability and long-term solidity of a masonry building.

Which blocks can be used with Thin Joint?

The success and accuracy of building a wall using Thin Joint construction relies on the dimensional accuracy of the blocks being used. Traditional 440mm long lightweight aggregate and dense concrete blocks from our range or from any manufacturer do not possess this level of accuracy.

Our Airtec range of aerated concrete blocks are perfectly suited to Thin Joint construction (as well as conventional mortar construction) and are the only UK manufactured block to possess the very tightest possible dimensional tolerance category of 'Thin Layer Mortar B' (TLMB). This category requires an addtional level of mortar bed flatness and coursing height parallelism of the block as well as tighter length x width x height tolerances. 

 

What are the benefits of Thin Joint?

There are numerous benefits to using the Thin Joint construction method to the designer, builder and occupants of the building. These include:

• A flexible method. Thin Joint canbe used on external cavity or solid walls, internal partition walls and seperating party walls.
  
• Enhanced thermal insulation. Up to 10% improvements in U-Values are possible in comparison to equivalent conventional walls.
  
• Increased airtightness. A greatly reduced proportion of mortar joints in the wall as well as guaranteed fully-filled bed and perpend joints reduces air-loss paths and maximises air-tightness of the inner leaf envelope.
• Better quality of build. The blocks in use are dimensionally accurate and inner leaf can be built ahead of the outer leaf thus avoiding mortar snots in cavities and poorly fitted cavity insulation.
  
• Faster and easier laying of blocks. Within 15 minutes, the thin joint mortar is set and the next course can be laid. This permits continual laying of courses and avoids the problems of settlement and 'swimming' of blocks associated with conventional mortar.
  
• Higher strength of walls. The adhesive nature of Thin Joint mortar results in a higher wall strength that that of an equivalent conventional mortar wall. This is recognised in Eurocode 6 (BS EN 1996-1-1 Design of Masonry Structures)
• Faster weatherproofing. The speed of laying using Thin Joint mortar along withno need to match up inner and outer leaf coursing heights means that the inner leaf envelope can be totally finished before the outer leaf goes up.
  
• Less waste and mess. No cement mixers,material silos are required on site. Airtec blocks are easily cut and shaped thus ensuring minimum waste and maximum utilization of the blocks.
  
• Comfort and energy saving over the life of the building. As with any masonry brick and block construction, the Thermal Mass of the building is significantly higher than that of framed buildings. This increased thermal mass has been shown to minimise seasonal temperature fluctuations within the building, increasing comfort and reducing the need for additional mechanical heating/cooling. This combines to greatly reduce the CO2 emmissions of the building over its lifespan.
  

More details are contained in our publication: 'Thin Joint Mortar Construction: A Detailed Guide'

What special tools and techniques are required on site?

Generally when using Thin Joint the overall techniques of building walls, accommodating movement, installing floors and roofs will be familiar to anyone who has ever built a masonry brick and block building. There are however some key differences in design and technique that need to be allowed for when using this method of construction:

• With mortar joints of only 2-3mm, the coursing heights of the blocks at floor, lintel and roof levels will be different to that when using 10mm conventional mortar. This can be avoided at the design stage but nevertheless the blocks are easily levelled down to required level using sanding rasps during the build.
• The Thin Joint mortar is a powder supplied in 25kg bags to which water is added. Only a bucket and electric stirrer is required - no cement mixers, shovels, sand, cement is required.
• The mortar is applied to the blocks using special scoops / sledges which ensures accurate and fully-filled mortar joints of the correct thickness.
• Flexible movement control mesh is applied along entire courses at certain levels to avoid movement and associated cracking as the blocks dry out naturally.
• The inner leaf (Airtec thin joint) can be built up independantly of the brick outer leaf. Matching of coursing levels of the inner and outer leaf is not important as helical twist steelwall ties are hammered into the inner leaf block face at the necessary outer-leaf course level.
• Special wall ties, movement and shear ties are availableall of which are quick and easy to use and specially designed for use with thin joint aerated blocks.

More details are contained in our publication: 'Thin Joint Mortar Construction: A Detailed Guide'

Where can I find further information?

Our Detailed Guide offers comprehensive advice and information for using Thin Joint.

For specialist advice, tools, ancilliary components and mortar, we recommend that you contact Thin Joint Technology Ltd (part of the Clan Ltd group) or visit their website at www.thinjoint.com.

Thin Joint Technology Ltd have been at the forefront of promoting Thin Joint construction in the UK for many years and have accumulated a wealth of expertise and experience second to none. As well as advice about using Thin Joint construction in practice, they can offer a demonstration service and a design service which will take building designs and convert them to Thin Joint construction ensuring maximum ease of build, maximum effectiveness and minimum waste and problems on site.