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Precast is manufactured from rods and mortar components, made to order, to a size and specification to suit individual project requirements. It is used for various applications internally, externally and fire rated. 

A precast panel system will speed up installation and offers many benefits, lending itself to projects where multiple panels are repeated or time is limited. 

For example:

A community project in Northern Ireland required an entire property renovation to be carried out over just three days with assistance from volunteered labour. The job was well planned, the panels were cast six weeks prior to the installation. Everything was fitted and sealed within a 30 minute slot, with ease.

General characteristics

Prefabricated glass block walls offer many benefits such as the advantages of being dry fix, ease and speed of installation and quality control (they are manufactured under factory controlled conditions, ensuring regularity of joints and consistency of mortar to guarantee a first-class, premium finish). 

Cold weather conditions do not affect the installation of external precast units – unlike in situ construction – and can be installed by site personnel.

Size restrictions will determine whether a panel can be produced on the basis of handling, logistics and health and safety. For larger areas, horizontally or vertically interconnecting panels are used which seamlessly join together to look like one panel.

When designing precast it is important to consider the restraint and fixing system for anchoring and securing the units safely to the perimeter opening, whilst incorporating the expansion joint. 

When planning and specifying precast, initial points to consider are:

  • The fire rating. 
  • Calculation of the opening size.
  • Restraint/clamping system.
  • Lead time.
  • How panels may connect together.
  • Access to site and area in which they will be installed.
  • How they will be installed in accordance with health and safety regulations. 

Characteristics of panels – joints and perimeter borders

Panels can be produced incorporating all different size glass blocks and patterns, the most common being 190x190x80mm. 

Joints are generally 10mm. This can be decreased to a minimum of 6mm or increased to a maximum 20mm. 

A condition of precast is that panels have to be produced with a perimeter border, vital for the purpose of restraint as well as production and handling. 35mm is the minimum standard width used and is suited to the two-part U-channel fitting system. 

TF30 and TF60 fire panels are also manufactured with a minimum 35mm, but generally 50mm perimeter border. 

precast installation


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