Design - Lintels, joist hangers, cavity closers

LINTELS

Airtec block walls can accommodate most types of lintel, in particular; Concrete Lintels, Steel Lintels and Box Lintels.
  • Construction should be in accordance with BS 5628-3 : 2005.
  • Wherever possible, the masonry should be set out so as to provide a full block under a bearing. Generally, lintels should have a bearing of no less than 150mm either side.
  • In solid Airtec walls, the inverted T-shape steel lintel can be used and the block chased out accordingly.
  • Specific calculations should be carried out in heavily loaded walls and consideration should be given to the use of load-spreading methods and suitable padstones.
  • A slip plane should be provided between the lintel and the bearing face to accommodate differential movement. 
 

JOIST HANGERS

Joist hangers may be used provided that:
  • They are compatible with aerated blocks with compressive strengths of 3.6N and above.
  • Installation is in accordance with the hanger manufacturer’s instructions.
  • The Airtec course to carry the hangers is level and at the correct height.
  • The hanger bears directly onto a complete block with the back plate flat against the block.
  • The gap between the joist and the back plate does not exceed 6mm.
  • The blockwork above the hanger is complete and matured before any load is applied to the hanger.
 

CAVITY CLOSING

To maximise the thermal insulation achieved by using Airtec blocks in external cavity walls, there are a number of points to consider during the design and construction stage. These points not only maintain the thermal integrity of the Airtec envelope and minimise cold-bridging, they also aid the accommodation of movement caused by dissimilar materials.
 
These details have assumed greater importance recently with changes to Part L of the Building Regulations and the increasing importance of methods for reducing emissions (e.g. SAP 2005) and increasing airtightness:
  • The easy cutting and shaping of Airtec blocks allow the formation of Airtec reveals at the vertical edge of window and door openings.
  • To avoid contact between dissimilar materials and associated movement problems, a slip-plane of dpc type material should be inserted between the vertical interface.
  • At the eaves level of the cavity wall, the cavity can be closed by laying a course of Airtec blocks flat to close the cavity.    
 
 
 
 
 
 
 
 

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