Work began this month on a large-scale project to repair 160 properties on a new housing estate in South Wales. The houses, which have a timber frame construction, failed a recent National House Building Council (NHBC) inspection when it was discovered that the properties were not structurally sound due to inadequate brickwork restraint.
The NHBC has roots dating back to 1936 and is now the leading independent insurance and warranty provider in the UK for new houses, as well as being an authoritative body for standard-setting. Their goal is to raise the standard of new-build properties while providing essential protection for buyers and, as a non-profit organisation, NHBC continues to reinvest in order to further facilitate its vital work.
The inspection revealed a common defect in new timber-frame house construction, namely that the wall ties used to restrain the building’s brick façade had not been fixed securely in the structural frame but had simply been nailed to the adjacent 12mm plywood sheathing. After the inspection, Twistfix were contacted by the housebuilders, one of the largest in the UK, to advise - we quickly arranged for several experienced building contractors to tender for the remedial installation of timber frame wall ties, with Newman Building Solutions being selected to carry out the work.
Twistfix self-tapping timber wall ties are incredibly efficient and are the most flexible available on the market today. CE-Marked to prove fitness for purpose in new-build construction, the helical ties are hammered into timber studs to create a screw-in connection; the other end of the helix is encapsulated within the mortar bed, using resin adhesive for retro-fit applications. Multiple drip points between masonry walls and timber frames are thus ensured, fully accommodating any differential movement in properties of up to 3 storeys high.
Wall tie replacement work on timber frame houses requires a great deal of skill explains NBS Director Steve Newman. 'Firstly we have to accurately locate the structural studs in order to ensure a good fixing point. We are installing the Twistfix ties at the rate of 4.4 ties/m2 and we currently carry out random tensile tests on 10% of the ties being installed to verify that performance requirements are met. The whole system has saved thousands of pounds for the housebuilder, whose only other option was to takedown and rebuild the brick facades'.
We look forward to hearing more from Newman’s as this vital project progresses.