There are plans to pump foam concrete into a void under the pavement outside The Empire in Bath city centre which has been neglected for years and is currently being propped up to stop it collapsing.
The Empire in Bath | Photo © Mareks Perkons / Shutterstock.com
The method is similar to that used to make the Combe Down mines safe.
The Empire was built around 1900, designed by the city’s architect. It was originally used as an hotel but requisitioned by the Admiralty at the start of the Second World War.
It was returned to its owner, Bath City Council, in 1989 and converted into 43 retirement apartments in the mid-1990s, with restaurants on the ground and basement floors.
The proposed structural remedial works are to the void under the pavement near the south-east end of the Orange Grove façade.
It is believed that the void is possibly waterlogged cellars from houses demolished when the landmark building was constructed.
The building is Grade II listed. The application which seeks listed building consent has been submitted to Bath & North East Somerset Council by residents’ property management group The Empire Bath RTM Company which says the situation needs to be sorted “quickly”.
It has the support of The Architect restaurant at The Empire.
The cost will fall on leaseholders who have previously said they were not aware the vaults were their responsibility.
A report submitted with the application says that the existing concrete and steel deck that forms the pavement area above the void was built around 1933. New support beams were installed in 1995 to provide strengthening to the original decaying deck/steels.
However, it was later discovered that the 1995 repairs did not include galvanized replacement steel beams and the leaks in the concrete slab above were not properly addressed.
The report adds: “The non-galvanized replacement beams were also installed tightly against the soffit of the concrete deck, which made it impossible to maintain the protective paint coating on their upper surfaces.
“The slab was found to be unreinforced and constructed from clinker concrete with brick aggregate containing sulphates which, when wet, create high acidity that can severely corrode any steel in contact.
“This slab was left unreplaced and therefore continued to leak. The resulting corrosion was likely due to persistent water infiltration through the roof slab, compounded by poor ventilation in the void space.
“History has now repeated itself, with the replacement secondary support structure also now become corroded.
“A series of temporary props were installed in 2021 to prevent collapse of the existing pavement above.”
The report explains that following a Bath & North East Somerset Council survey of vaults within the city centre, safety concerns were raised regarding the “parlous” state of this existing void and the “potential impact this could have on the public realm above”.
A detailed structural assessment was commissioned and found that the void space had been impacted by water through cracks within the decaying concrete deck. “This water ingress has severely corroded the steel beams which provide primary support to the pavement above.”
The structural report recommended that a series of ‘props’ be installed whilst a permanent solution could be found. These remain in place and are monitored regularly.
The report says research has revealed that at the time of the conversion in 1995, there was a proposal for this void space which would have involved installing a new tanking system across the pavement deck.
“However, this was not done, partly due to costs and partly since the head lessor (then a Pegasus company), had been granted both obligations and rights by the freeholder (B&NES Council) to develop the Colonnades and associated Undercroft areas beneath Grand Parade.
“Despite several design feasibility studies, these proposals were never pursued, and without the installation of waterproof protection, the concrete deck and supporting structure deteriorated, resulting in increasingly damp conditions within the void space.”
The report says the previous managing agents “did not seem to realise” that this underground pavement void area was within its repair and maintenance remit which had resulted in “years of neglect” of this redundant space.
This neglect was one of the reasons contributing to the residential leaseholders exercising their ‘Right to Manage’.
In mid-2022, the new RTM Company took over responsibility and appointed new managing agents, 3Sixty Real Estate to oversee building repair and maintenance.
Three options have been considered; Option A involving a full concrete deck /steel beam replacement; Option B to infill the void with lightweight foam concrete, and Option C to retain the existing props.
The report says: “The applicant, along with the commercial leaseholder, are seeking approval to progress with the only viable Option B by infilling the existing underground pavement void using a low-density foam concrete product (e.g. Porofoam by Cemex).”
It adds: “Estimates for this option were half that of the full repair cost (then circa £250k, but now most likely to be higher due to inflation and use of additional drainage membranes); which although still significant, was the only viable option sensibly available to the residential and commercial leaseholders to safeguard the public pavement for future years ahead.”
The foam concrete will ensure that the existing corroded steels are therefore no longer relied upon for structural stability. The report adds that it also eliminates the need for extensive removal and replacement of the existing steelwork, concrete deck and public pavement/footpath, avoiding prolonged disruption and a likely lengthy closure of the restaurant above.
Before any works are undertaken, an assessment of the drainage will be made to ensure it is functioning correctly and if necessary, repairs will be carried out.
Temporary protective hoarding will be provided during delivery by truck of the pre-mixed foam concrete and the installation works. Access to the restaurant entrance will be maintained.
The application says the proposals will not harm the listed building or its setting within the Conservation Area and World Heritage Site.
In a statement, The Empire Bath RTM Company says: “The simplest and cheapest course of action, would be as described in Option C, to install more temporary supports and steel plate sheeting and prop up a leaking concrete slab, which is what was done by the developer (circa 1995).
“However, we do not feel such an option would be the professional course of action to take, as the problem would resurface and the work would need to be patched up again.
“We are therefore supporting the request to undertake the work outlined as Option B – the infilling of the void with lightweight foam concrete.
“Taking all the factors into account, although this is not the cheapest option, we believe this to be the best and most responsible way forward.
“The work needs to be done quickly for safety reasons, but also because any further inflation will put a huge strain on leaseholder finances.”
The Architect restaurant says in a statement: “The current proposal allows us to retain full access to our property, shortens the duration of the project and subsequently the disruption to our business and hence we are supportive of this solution / application.
“Alternative methods would involve the loss of our main entrance resulting in a significant reduction in capacity and a likely closure of our business for a prolonged period of time (c. 20-24 weeks).”
The plans include retaining a small area below the external restaurant steps to allow maintenance access.
The planning reference is 24/04436/LBA. The consultation closes on 2nd January.
