Thin Joint Construction

What is Thin Joint Construction?

Thin Joint 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 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 emissions over the building's lifetime and yet maintain the familiarity, comfort, stability and long-term solidity of a masonry building.


  • External Cavity Walls
  • Acoustic Separating / Party Walls
  • External Solid Walls
  • Internal Partition & Flanking Walls


  • Faster and easier laying of blocks
  • Faster weatherproofing
  • Less waste and mess
  • Flexibility
  • Thermal mass
  • Quality of build
  • Stability and strength
  • Enhanced thermal insulation
  • Increased airtightness
  • Acoustic insulation
  • 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 additional level of mortar bed flatness and coursing height parallelism of the block as well as tighter length x width x height tolerances.

  • 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 independently of the brick outer leaf. Matching of coursing levels of the inner and outer leaf is not important as helical twist steel wall ties are hammered into the inner leaf block face at the necessary outer-leaf course level.
    • Special wall ties, movement and shear ties are available all of which are quick and easy to use and specially designed for use with thin joint aerated blocks.