Secured walls allow store expansion to proceed in St Helier

The De Gruchy department store has been a St Helier landmark in New Street since 1824. Now, following redevelopment and the addition of a new retail area, it has doubled in size and also contains one of Next’s largest UK stores.

The remodelling of the store meant that an internal party wall, originally built as two independent skins with a varying gap between them, became an exposed external wall. At ground floor the gap was up to 600mm wide narrowing to 120mm at higher levels and just 65mm where it passed floor levels. Although effectively acting as a cavity wall it had no wall ties connecting the two skins and fell far short of the requirements for an external wall. The two skins needed to be effectively secured, without disruption as internally it remained a live retail environment.

A further requirement of the redevelopment was for the installation of a new retail floor using Posi-Joist construction and taking support from the existing building walls. The joists were supported by timber wall plates that had to be bolted to the internal faces of the existing walls, which were of mixed rubble, granite and brick construction and in poor condition in some areas.

The Helifix Solution

Using RetroTie remedial wall ties and SockFix grouted anchors, Helifix devised an efficient solution that respectively connected the leaves of the external wall and reliably secured the wall plate to the rubble walls.

• Extremely effective in rubble walls, SockFix anchors were used to secure the wall plates. Comprising a stainless steel bar in a durable fabric mesh sleeve, the SockFix anchors were inserted into a core-drilled clearance holes before being pumped full of grout to expand and fill any voids and become an integral part of the structure. The SockFix threaded bar was left proud of the wall to receive the pre-drilled wall plate and enable a bolted connection.
• The 400mm long M16 SockFix Anchors were installed at 300m centres with each anchor requiring a tensile capacity of 2.1kN. A 3kN test load was successfully applied to each anchor after installation to ensure they had achieved the high loading requirements.
• The 500 RetroTies were installed externally so caused no disturbance to the inner face or to retail trading. The ties were inserted through clearance holes drilled in the outer skin and hammer driven into the inner wall for a solid mechanical connection before being resin bonded into the outer skin.