Royal National Theatre

Designed by Haworth Tompkins Architects and constructed by The Garden Builders

Royal National Theatre Garden

The works undertaken at the national theatre were broken down into two main sections. The Weston terrace, level 1 main pedestrian entrance and the Olivier terrace, level 3 public terrace. The biggest hurdle to negotiate while working on this project was the theatre was at all times open to the public and shows continued as scheduled. This meant the usual high attention to health and safety was absolutely paramount as the general public was always in close proximity to sometimes hazards works. During the build daily safe starts meetings were held with every contractor to ensure the health and safety of everyone on and around the site was priority number one. Each week the supervisors from each contractor meet with the main contractor to walk the site and ensure that actions implemented from the previous week were in place.

As the theatre remained opened to staff and the public 'noisy work' times were planned each week in advance and daily 'noisy work 'were to be completed within the allotted time restraints. The National Theatre is a concrete building with a honeycomb coffers set into the ceilings of the entire building. So any work on the structure would reverberate and travel through the entire building making the necessity of a daily noisy works programme.

The Weston terrace works were broken down into the following tasks

* The removal of the existing concrete paving slabs and the build-up on top of the roof. All waste was transferred to skips via a goods hoist. All waste removed from the terraces was logged and monitored to ensure recycling of waste materials was optimised.

* The removal of the existing waterproofing membrane from the roof surface and strip out redundant power and lighting cables. This involved clearing the entire western roof and scrapping back the old membranes and removing to skips.

* Installation of new Alumasc hot melt roof system to the exposed roof surface. These works were undertaken by specialist contractors working under the Garden Builders, who managed the installation throughout.

* Install new concrete paving slabs to the entire western terrace laid on pedestal feet above the new hot melt roof and laid on roof spacers on the existing insulation. The paving was laid at a 45 degree angle to the perimeter walls. Throughout the terrace approximately 1800 new slabs and 5400 pedestal feet were installed on the terrace

* Install new Welsh Blue Pennant paving that was engraved with the name of the generous donor who had donated money to the theatre to help with the NT future works. A total of 420 were laid around the entrance from the riverside walk way.

* Design, fabricate and install a stainless steel baffle to hold LED tape lighting under an overhang on the perimeter walls. The lighting was to illuminate the terrace at night as well as being part of the emergency lighting that would come on in the event of a fire. As well as the lighting installation there were 13A, 32A 1 phase and 3 phase command sockets installed for use when functions are to be held on the terrace. All the containment for the new power cables was run under the paving in galvanised conduits and weather proof junction boxes.

* 22 roof penetrations were made into the entrance foyer below the terrace to accommodate new CCTV, speakers, lighting and monitors. All the penetration had to be pin pointed from below to ensure the correct position and then all points were ferro-scanned to ensure no reinforcing rods were damaged during drilling. Once all holes were drilled containment was run via the lift shaft located on the terrace and the relevant cables run through to their position. All the penetrations were then encased in a pitch pocket of hot melt water proofing to ensure the roof remained water tight. The entire roof was at this point leak tested using an electrical testing device which can pin point any leaks.

* Fabricate and install hardwood iroko benches with integrated planting beds. To add some colour and interest to the long northern wall of the terrace a hardwood bench was installed to offer seating and seasonal planting. This bench was installed on pedestals and the internal planter lined with drainage membranes and then a LECA layer covered in terram to ensure free drainage within the planter.
The Garden Builders were also responsible for liaising with other contractors who were contracted in by Lend Lease (the main contractors) to install other working elements, these included signage contractors and a new stair case to connect the terrace with the restaurant on the balcony above on level 2. On this terrace alone 30 skips of waste were removed for recycling, 600m2 of roof was water proofed, 2200 new pavers were installed and around 300 metres of baffle with LED lighting were fixed. During the build on the Western terrace each stage had to be signed off and witnessed by the design team and the client at the completion of each task. The Olivier Terrace works were broken down into the following tasks.

* Strip out the old planter on the terrace and remove all excess soil off site.

* Mark out for the four new larger planting beds and decking area and remove all surplus paving and any build up down to the water proof membrane layer.

* Within the four planter / benches as well as on the perimeter walls we installed data points, 13A,32A single and 3 phase command sockets as well as extra conduits to allow the future installation of audio systems for events. The same baffle was used again on all perimeter walls.

* The biggest challenge faced on the Olivier terrace was the installation of 6 no. canopy anchor steels which are situated under the corners of the two L shaped benches either side of the decked area. These steels (each weighing approx. 200kgs) were set directly to the roof screed which is below both the waterproof membrane and the insulation layer below. The exact position of each steel had to be perfectly accurate as did the layout of the bench above. The steels are fixed down into the walls of the coffer ceiling below and in order to be exact the ceiling below was mapped and transferred to the roof above. The canopy anchors were then positioned and drilled out to 400mm to allow 16mm threaded stainless to be chemically fixed in place. Once fixed each anchor was pull and shear tested and documented to prove the fixings could with stand the forces the shade sail may have to with stand. After the testing was completed the areas of roof membrane and insulation were replaced and tested for leaks.

* On this terrace there was requirement to upgrade the existing power and distribution boards located in an electrical cupboard located on the eastern side of the terrace. All the new cables and containment was run back to this point and then new holes were drilled through the structure to allow the extra cables into the building. The National Theatre is a listed building so each hole into the structure had to be agreed with the English heritage prior to drilling. Once the holes were drilled new containment was installed to cover all exposed cables running into the building.

* As well as the electrical install irrigation was required for the large planters set on the terrace. A new water feed was brought up to the terrace via an internal riser and then drilled through the roof and run into a corner of a bench so an irrigation timer could be installed and each planter could be watered separately. The new water source is feed from a new water bore located on the site under the car park. This ensures the theatres water usage from the main supply is limited.

* Once all the services and steels were in place the new hardwood benches/planters were installed. These were set out from drawings and set snuggly over the canopy anchor positions and then aligned with the perimeter walls and each other. The benches were bolted together and levelled using pedestals. Then all remaining sockets and data points were installed within the bench seating lids and the LED strip lighting was installed under the front edge of all the benches. As well as the perimeter LED's there are also 19 no galvanised posts rising above the planters and each is fitted a tube LED light to illuminate the decked area.

* Prior to soil being installed all the planters were lined with geo-textile and a drainage membrane system was incorporated to ensure free drainage from the beds.

* The area between the two L shaped benches was laid with machined iroko decking and fixed with stainless steel wurth decking screws. The decking is laid onto a frame which is levelled using the adjustable pedestal feet and left flush with the paving at either entrance to the decked area.

* Once all the tasks were completed the paving was re-instated around the perimeters, benches and the decking. Again as with on the lower terrace the paving is laid at 45 degrees to match the ceiling coffer layout below.

The complexity of the build which most people will never see was a challenge that the on-site team meet head on and delivered a finished product that they and the client are very proud of. Although the scale of the installation is large the attention to detail was maintained throughout the build. To have given the opportunity to be involved with the modernisation of such an iconic building was a privilege and to have been able to finish the works to such a standard that the client was pleased with was great. Both terraces are now open to the public and are used by both theatre goer and public alike.

Following the successful installation of the seating planters on the Bank of America terrace, the Royal National Theatre were keen to add some rather needed greenery to the stark Weston terrace as it was lacking any real impact. They instructed the architects to come up with a re-design that worked around the Donor Stones and seating benches previously installed and which would bring a softer feel to the terrace by incorporating planting. The design required four matching style planters to be positioned amongst the Donor stones and incorporated LED strip lights to match all other planters on the terraces.

The terrace was open to the public during the works so it was very important we followed guidelines set out by the Nation Theatre on Health & Safety whilst working on site. Large areas of paving were lifted and Donor Stones re-located to new locations to accommodate the large planters.