Auditorium Foundations

Band Pit, Access and Ventilation

As well as working outside the building, there has been a lot of activity inside the auditorium and under the stage.

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The plan for the auditorium is that it should not feel too different in look and character to what was there previously. However, significant works are required in order to create a new removable band pit; improve access from the front door of the building to the auditorium; make better use of space; increase the seating capacity; and to improve heating and ventilation.

Ventilation and Heating

The heating and ventilation in the old auditorium left a lot to be desired. Ventilation was previously provided by an historic old system that made so much noise it was impossible to use it under show conditions. Heating was provided by a smattering of radiators around the walls of the venue that distributed the heat unevenly to the audience.

We frequently had people on the verge of passing out with the heat in the upper levels in the height of summer, or having to wear their coats, hats and scarves if they sat on the front row in the middle of winter.

Much earlier in the design when audiences were still in attendance, Max Fordham, our Mechanical and Electrical design consultants, carried out CO2 testing in the auditorium. I think they were surprised that anyone was still awake with such low amounts of oxygen left at the end of a long busy show.

The age of much of the mechanical and electrical system meant that some bits had already failed completely and had temporary systems in place, and others broke down on a regular basis needing constant repair and attention. The bits that were working were also incredibly inefficient from an environmental sustainability perspective. This meant it made most sense, to completely replace the heating and ventilation systems.

Our strategy is to create what is known as a plenum under each level of the auditorium. This is a large void under each seating area that can be supplied with fresh air that comes out through hundreds of small grills in the floor and behind seats. This ensures that we deliver air at the right temperature across all levels and areas of the auditorium. Hot air can then be extracted at the ceiling above each tier.

These plenums will be supplied by a new air handling system that will deliver air at ground floor level through a trench from a plant area to the north of the auditorium that runs into a newly excavated and formed void under the stalls seating area. Under the dress circle and gallery seating less work is required as there are already significant void spaces that can be tidied up and sealed for the purpose.

As part of an audit that was carried out in light of Covid-19, the capacity and specification of the air handling was upgraded even further, enabling a complete air change every 7 to 8 minutes. When we reopen the main auditorium will be provided with a healthy supply of 100% fresh air; all the more important for a building that will be operating in a post-Covid world.

Bandpit

At the front of the auditorium, we are creating an area of removable floor with a band-pit. This requires some excavating and a new foundation being laid. We have never had this facility before at the Citizens Theatre and previously bands or musicians at the front of the stage have badly obscured the view of the audience and required more seats that necessary to be taken out to facilitate them. No longer will children have their view blocked by a glockenspiel player! (as I remember on one particular Christmas show).

Access

We are significantly lowering the entrances to the auditorium at the back of the stalls so that the floor slopes up to the back of the seats instead of down (as it did previously). This is what allows us to level out the foyer and get rid of the ramps and stairs that made access more of a challenge.

These changes in level also allow us to create two new boxes with flat level floors, that better serve wheelchair users in particular, on either side of a new central control room. This gives new options for wheelchair users in addition to those we had previously in the stalls. There will also be new positions available for wheelchair users at dress circle level.

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Building Work In The Auditorium

The original plan for the bulk of the auditorium was to lift the floor, scrape out the loose material from the dirt floor underneath, and pour a thin layer of concrete screed around the existing structure to seal the void.

When I last posted about the auditorium in June 2020 we had already removed the auditorium seats, taken up the carpet and started to take down the old rooms at the back of the auditorium.

We finished removing the old control boxes and began to lift the floor to get access to the void space underneath.

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The joists were in much worse condition that previously anticipated. They were badly warped, had problems with shakes, the spacing was a bit too far apart, and what was holding them up was far from ideal. Some were held on wonky wooden posts sitting on random blocks of sandstone balanced on bits of half brick. There was also evidence of woodworm and rot. (It’s no wonder the floor used to be so squeaky!)

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There was a huge amount of debris under the floor that needed taken out and the ground level was a lot higher than anticipated in some places meaning more excavation would be required to form the plenum space. The original plan was to work around and augment the existing structure but with the timber and foundations not fit for purpose, and the excavation now requiring mechanical diggers, we were left with little choice but to take everything out and start from scratch.

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Having cleared the space, machines were brought in to excavate the band pit and create the void required for the ventilation plenum under the seating area.

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After excavation a damp proof membrane was installed followed by rebar ready for concrete to be poured.

White packers lift the steel rebar so that it ends up in the middle of the concrete. The column foundations have been wrapped in membrane and rebar as well.

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All three levels had been poured to form the band-pit, the air plenum, and the access and control room areas at the back of the auditorium. The concrete was then polished and sealed, ready for the new floors to be built back up on top of a good solid set of foundations. The next step will be to install the ventilation system and timber floors. Hopefully it won’t be too long before we have it carpeted, the seats reinstalled, and audiences back in.

There has also been fantastic progress assembling the steel frame for the new build elements of the project, and major alterations backstage and understage which I will cover in new blogposts soon.

_{^{© g.sutherland = photos by Graham Sutherland (all rights reserved)}}