The architectural brief was to transform a disused external tarmac courtyard space lacking function and purpose into a contemporary glazed atrium enclosure within a on-site construction programme of eight weeks from commencement.
We as Specialist Façade Contractor played a pivotal role in this projects delivery, our workpackage were critical to its practical completion.
Our project management technique was hands on throughout this period. 0ur façade workpackage included:
- Capped Stick curtain walling.
- Architectural cladding.
- Architectural louvers.
- Pyramid glazing.
- Lean to, sloped glazing.
- Entrance doors.
Internally, looking up through the architectural sloped roof glazing, one can see that this new build extension makes best use of natural daylight around its perimeter edges. 16m square in plan, daylight filters naturally into the atrium and adjoining classrooms through tall refurbished existing windows in the external fabric.
The primary structure of this architectural atrium space is steel framed. Standing independently of the existing three courtyard walls, a wide gutter acts as a visual break between new vertical circular columns/ horizontal I-beams and old masonry walls.
The steel was erected to very tight construction tolerances to enable a single hip rafter at each corner. On-site levels were taken to ensure that this happened as to minimise the requirement of shimming the overhead roofing system. Tolerances in the as-built steel ope widths were accommodated by strategically placing head and cill transoms.
The I-beam to the base of the lean to rooflight glazing forms a vertical edge to the gutter upstand. It presence alters the natural slope of the glazing, making it shallower in pitch, a strong contrast to the pyramid structure.
Lean to Roof-Light Construction
The standard lean to stick rafters were factory fabricated and erected on site in stick form. Each side of the architectural rooflight was assembled to the corner and levelled prior to fixing. All brackets are concealed above the steel structure hence no visible fixings internally.
Each corner was fabricated as bespoke on site to suit the as built conditions. The hip mullion box is size is deeper due to a 4m clear span. Notching of mullions was a requirement at head and base to suit the architectural structure and the available interface built up roof zone at the head.
Fabricated in-house and transported to site as a complete unit, this pyramid rooflight structure has some interesting features. The upstands are fabricated in steel into which two ventilation extracts are located. Externally, an architectural louver runs around the outside of the vertical membrane providing weathering. Its blades are pressed, deep enough with overlapping blades; the atrium can be ventilated without ingress through mechanical extracts.
As part of our value engineering process we looked at various design solutions to the architectural intent. The simplest of these been the most cost effective and performance related. The sides were constructed in water proof ply on to which a 150mm rigid board insulation and roofing membrane was secured. Secret fixed vertical rails were fitted to this structure on to which horizontal pressed aluminium blades were fixed. The outcome aesthetically pleasant , increased performance and cost effective.
ADT Interface Base Detail
The interface detail to the base incorporates a 3mm pressed architectural flashing which is glazed continuously into the raking mullion stick and horizontal transom members.
The intent of the architectural metal flashings was to conceal the unsightly edge of the I-beam to rafter connection. This detail was devised through value engineering. Different options were looked at but cost and performance directed our designers to this interface solution.
This architectural cladding flashing overlaps the glass by 40mm. It is structurally face sealed to it horizontally to allow water run-off preventing build-up of dirt and staining.
Its vertical face extends down the face of the gutter and is fully integrated with the gutter roofing member upstand. The membrane is notched to allow the raking mullion drain to the outside of the membrane. Rigid Phenolic board insulation runs across the inside of this flashing addressing thermal issues. An air tightness seal is incorporated internally.
ADT Interface Head Detail
There were a number of façade weathering risks to the head detail. Due to change in slope of the roof glazing to the pyramid structure, there was a concern that this interface could catch and hold water leading to degradation and ingress locally.
This ADT interface detail has two weathering seals.
The primary sarnafeld roofing membrane is glazed into the mullion / transom forming the traditional primary seal.
The secondary weathering seal consists of a welded preformed continuous flashing masking the primary seal preventing blow back, protecting critical glass to aluminium roofing connections.
As part of the value engineering process, the glass selection impacted greatly on the environmental strategy. As this atrium enclosure is air conditioned, different glass configurations were analysed in respect of impact on solar gain (G value), Light Transmission (LT) and u-value.
The latter two features been more relevant as the existing walls offered reasonable solar shading. Through value engineering, a solar neutral glass SN 70 from guardian offered enhanced performance at the most reasonable cost. Its soft coating offers solar protection and thermal conservation whilst allowing significant light through the architectural sloped glazing.
The bay windows to the front were originally conceived as architecturally frameless structurally clamped glazing.
Using ADT FA+CE value engineering, the architectural fenestration was changed to capped so that the performance of the face glass could be enhanced. The cost saving enabled the face glass to take on additional safety and acoustic features.