What is BS 7456 - Cavity walls filled with polyurethane (PUR) foam systems about?
BS 7456 gives recommendations for the installation of rigid polyurethane (PUR) foam systems complying with BS 7457:1994, which are dispensed on-site, to fill cavities of the maximum width of 150 mm of suitably constructed external walls of maximum continuous cavity height of 12 m which have masonry or concrete inner and outer leaves, thereby providing additional thermal insulation to such walls and simultaneously, especially in the case of walls with damaged wall ties, improving their structural integrity.
Note: Walls built of random rubble are not covered by this code.
Who is BS 7456 - Cavity walls filled with polyurethane (PUR) foam systems for?
BS 7456 on Cavity walls filled with polyurethane (PUR) foam systems is useful for:
- Construction industries
- Civil engineers
- Contractors
- Builders
- Civil engineers
- Tester of cavity walls
- Manufacturers and suppliers of wall equipment
Why should you use BS 7456 - Cavity walls filled with polyurethane (PUR) foam systems?
A suitable polyurethane foam system is injected into a masonry cavity wall by injecting the liquid polyurethane system through properly spaced holes in the outer leaf. The polyurethane foam system expands in the cavity and sets to become a substantially closed-celled cross-linked rigid polyurethane foam which is strongly adhered to the inner and outer leaves so that these leaves become bonded together.
BS 7456 specifies a study of all relevant drawings, if available, concerning the building structure, identification of any gaps which will allow the polyurethane foam system to escape from the cavity (e.g., gaps around windows, skirting boards, and at the top of cavities) and an inspection of the cavities using a borescope to assess.
BS 7456 benefits you:
- To ensure that the polyurethane foam system reaches all parts of the cavity to be filled
- To ensure that the polyurethane foam system does not penetrate areas of the building where its presence could be deleterious
- To avoid over-pressurization of the cavity which could result in structural damage
- To ensure that the polyurethane foam system is not pumped into anyone’s injection point for longer than its cream time
Overall, BS 7456 defines what are suitably constructed external walls and indicates essential procedures and precautions necessary to optimise the filling process.