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External Wall Insulation Programmes

Meeting the load requirements of external insulation panels

Local authorities and social housing landlords are looking to improve the thermal insulation of their housing stocks to lower fuel consumption, costs and carbon emissions while meeting current regulations and improving the living standards of their tenants. Where those homes are solid wall properties, prefabricated houses or precast concrete high rise buildings with narrow cavities, the use of rendered external insulation panels is popular and can improve the thermal U value of the walls by some 75%.

However, if the external elevations are unable to support the additional load of the new insulation and decorative finish due to weak, corroded or insufficient wall ties, these must be replaced or supplemented with new ties. If the inner skin or piers are constructed from clinker blocks, concrete or dense material, secure wall tie installation can be very difficult and unreliable, particularly as engineers may specify pull-out loads larger than the usual 1kn to account for the additional loading.

Helifix one-piece, helical stainless steel remedial ties are able to satisfy these varied conditions and provide property owners with a rapid cost-effective solution. Frequently the DryFix tie is appropriate, which is rapidly installed using a special tool to power-drive the tie into both leaves via a small pilot hole, which is easily disguised. It requires no grouts, resins or mechanical expansion so can be load-tested immediately to establish its suitability The requirements of the engineer, contractor and property owner are all satisfied, quickly and economically.

Case Studies

London Borough of Hammersmith & Fulham

Three 24 storey 1960’s tower blocks had a major ecological upgrade involving the fitting of extensive insulation, external cladding and solar panels to improve energy efficiency and enhance their overall appearance.

The structures comprise a concrete frame, lightweight concrete block infill and a brick outer skin. Project engineers, Carter Clack, chose Helifix to undertake reinforcement of the calcium silicate brickwork in stairwells on all three blocks to ensure these areas were strong enough to take the weight of the external over-cladding system and render.

An innovative technique, involving interlocking 23,000 bonded ResiTies and 15,000m of HeliBars in the six stairwells, connected the inner leaf to the main structure and enabled the HeliBars to distribute the wall tie loads through the entire face of the outer leaf masonry, providing greater resistance to wind loadings. Once the stairwell masonry had been fully secured, connected and reinforced, the external cladding and rendering of the towers could proceed.

RCT Homes, Penywaun, South Wales

Constructed with a clinker block internal skin, a concrete external skin and just a 50mm cavity, 170 properties owned by the largest social landlord in Wales were to be upgraded to meet current thermal insulation requirements.

Engineers determined that the strength of the external walls needed increasing in order to bear the weight of the new external cladding system. They stated that the new wall ties must have an enhanced minimum pull-out of 1.6kn while the contractor wanted ties that could be rapidly and easily installed as the contract was on a tight timescale.

Following on-site testing, DryFix remedial ties were specified as they satisfied all the requirements. Installation was rapid and trouble-free and the project was able to remain on schedule.