A CRANE WAS ERECTED IN THE MIDDLE OF THE SITE TO OFFLOAD STEELWORK AND THE BUILDING EFFECTIVELY WENT UP AROUND IT
The Ropewalks is one of Liverpool's historic conservation areas.
Streets run in long straight lines for over half a mile, which allowed ropemakers in times past to stretch out and twist their lines in what was a thriving industry serving ships in an equally flourishing port.
These streets are now home to Liverpool's creative quarter, with old warehouse buildings converted into commercial, retail and creative-use spaces. At its heart sits the Vanilla Factory, a £1.7 million mixed-use scheme designed by ShedKM Architects for developer Urban Splash. The new building, on a tight, cleared site between a brewery building and an 18th-century warehouse, stitches these two older structures together at second-, third- and fourth-floor levels by breaking through their party walls.
The core of the scheme is the modern infill building, with its composite steel and concrete frame. The frame's 5.4m 2 structural grid extends from the internal structure through the front facade into an expressed external streetscape volume, which has been created by setting back the front facade about a metre from the frame. The new pavement-level space creates presence for the ground-floor retail unit, breaking the frontage of the street.
The main steel frame was based on a modular grid, with vertical steel columns producing a 3.6m floor-to-fl oor height and horizontal I sections at 5.4m intervals. A concrete floor was cast in situ at each level over a hollow-rib permanent steel shutter system.
The entire RHS structural frame was challenging to fabricate. It had to be designed to the dimensions of the surrounding tightly packed streets and for the constricted site, which had no lay-down or storage space. Steel sections had to be short enough to fit on to a truck that was able to negotiate the tight streets. A crane was erected in the middle of the site to offload each day's early morning steelwork delivery and the building effectively went up around it. Only after the crane was eventually taken down could the gaps in each floor be fi lled.
On the front elevation the grid continues as an exposed structure of 300 x 200mm fully welded hollow steel sections, with a paint finish. The front facade is pierced by the steel frame - but only by the webs of the floor beams. Their flanges have been stopped off inside the facade. Because the extended webs are inadequate for structural stability, twin plates were fixed to either side of the webs to transfer the floor loads to the external RHS frame. This arrangement also allowed connections to be neatly arranged vertically around the horizontal axes of the frame (see Working Details, pages 54-55).
The removal of the flanges of the beams inevitably compromised their stability. Stability was re-introduced to the structure by neat horizontal bracing of steel rods at each floor level, connected with stiff cleats to the structural fascia panels and back to the floor beams.
The entrance area at ground floor is dominated by a composite steel and timber staircase. A massive 25mm steel plate acts as a balustrade, spanning as a single beam to the first fl oor, solid enough to stand its ground without buckling, yet elegant enough to be an architectural expression rather than just a structural device. This steel balustrade of singularly monolithic proportion is offset from the supporting structure of the building to create the effect of flights of stairs that seemingly float. Bridging steel sections span to the wall at a half landing and upper landing.
'Beams' of solid timber treads span between floor and half landing, and from there to the upper landing. These seem to rise without support - there are clear 50mm gaps between the wall on one side and the steel balustrade on the other. The overall effect is that each component is there of itself, in a structure where each element has been pulled slightly apart.
One reason the facade was set back was to bring as much natural daylight into the building as possible. With high buildings immediately opposite in a very narrow street, daylight was a scarce commodity, even though the building faces south. The recessed facade allows light to filter in over facing rooftops, especially in the early morning and late afternoon. External aluminium Luxuflex facade louvres provide solar shading as well as privacy from people working in the offices immediately across the street.
The external blinds are controlled by occupants at each level and can be opened to allow in more daylight on a dull day or pivoted to deflect sunlight, reflecting it on to the ceiling. Their operation by occupants gives the facade an active characteristic.
The whole assemblage achieves a clean simplicity for this new building in a historic context, its vitality coming from the layering of its individual elements.
A MULTI-LAYERED FACADE The elevation inverts the structure beyond the line of glazing and shading, thus piercing the envelope in order to transfer floor loads to the external frame.
Stopping the flanges of the floor beams within the building, and extending the web proved structurally inadequate, and was replaced with the twin plate connection allowing the connections to be arranged vertically on the horizontal axis of the frame. To avoid compromising the stability of the floor beams, 80mmdiameter horizontal bracing at each floor level connects to the structural fascia panels and back to the floor beams with stiff cleats.
The twin plate connection and external RHS frame were both erected and welded on site as part of the primary steelwork, followed by the installation of concrete hollow rib floors and secondary steelwork - mullions and cladding rails. Timber-framed aluminium cladding panels were then fitted at each floor level. The timber frame forms a recess between the floor zone and glazing, and enables the top and bottom of the doubleglazed units to be concealed.
This conveys the impression of continuous glazing between each storey.
External louvres were bracketed off the aluminium fascia plates, with guide rails fixed to mullions. The facade was completed with structural fascia plates and bracing.