Saving Face

Facade-retention methods in Liverpool's derelict terraces

Ian Weir

71 Shaw Street: this once fine Regency terraced house had been destroyed by decay following vandalism and years of neglect. Saving even the facade was a challenge.

Despite a century of industrial decline and heavy bombing in World War II, Liverpool has retained a rich heritage. With over 2,500 listed buildings, it is one of Britain’s finest Victorian cities, and in 2004 its mercantile, maritime core was accorded World Heritage Site status. However, in 1991 English Heritage’s buildings at risk survey had revealed that over one third of Liverpool’s listed building stock was either in poor condition or vacant and therefore at risk, or at best vulnerable to becoming so. In the economic circumstances that then prevailed, private owners in many parts of the city found property values too low and redevelopment options were simply not viable.

The Planning (Listed Building and Conservation Areas) Act 1990 and the Town and Country Planning Act 1990 provide local authorities with enforcement powers to require owners to undertake works to listed buildings that are falling into disrepair. However, local authorities are often reluctant to use these powers, particularly in such difficult economic circumstances, as noncompliance requires the authority to undertake the works in default. Few authorities consider that they have the financial resources to commit to such action.

Nevertheless, for the past few years Liverpool City Council has been taking its responsibility very seriously, turning to external funding agencies for help. Its strategy attracted the support of the government through its regional development agency, the Heritage Lottery Fund through a Townscape Heritage Initiative, and English Heritage through HELP, the Historic Environment of Liverpool Project. The strategy was also supported by notable local community leaders and the local press, which ran a campaign entitled ‘Stop the Rot’. Formed in March 2001, this integrated initiative gave the city council the confidence to deliver the ‘urgent works’ notices required.

Technical design support was given by 2020 Liverpool, an organisation set up in 2003 by Liverpool City Council in partnership with Mouchel to provide property and professional services to the City of Liverpool.

An initial ‘rapid assessment’ was undertaken to prioritise which properties on the register of buildings at risk warranted urgent attention. Liverpool City Council then served a number of Section 54 (urgent works) notices together with Section 55 (cost recovery) notices. In a few cases, owners incapable of complying with the notices have negotiated for the works to be undertaken by the city council. In two cases the city council served a Section 48 (repairs) notice in the knowledge that the owners would continue to default, and that ultimately a compulsory purchase order (CPO) would be required.

The following two case studies illustrate two projects which, sadly, had decayed to the point where only the facades could be saved. These were retained with the cooperation of the property owners and considerable ingenuity.

64-72 SEEL STREET, LIVERPOOL

This Grade II listed terrace of Georgian town houses on the south-west side of Seel Street was constructed in the late 18th century. The properties are of traditional load bearing masonry construction, comprising three storeys constructed over basements.

The houses had been vacant for many years and parts had been gutted by fire. The terrace had been reported to be in a dangerous condition threatening a public highway. Consideration was given to the need to serve a Section 77 (dangerous structures) notice on the owners, but it was agreed that the future of the buildings would be better protected if the buildings at risk protocol was adopted. Following the initial assessment of its current condition, an urgent works notice was compiled in consultation with the buildings at risk officer from Liverpool City Council.

Structural surveys and condition appraisal reports carried out at that time had noted that these buildings were in a severe state of deterioration. Decay had led to the progressive collapse of roof structures followed by internal floors, together with several external load bearing walls to the rear. The reports concluded that the buildings were in such poor condition that internal access was not permissible. This presented a problem, not only for its inspection, but also for its conservation, and it was concluded that only a facade retention scheme was viable. This would enable safe, phased access from the rear to permit the removal of the debris from various collapses and the lowering of unstable party walls.

2020 Liverpool was instructed by the city council to assess the feasibility of saving the front facade.

At higher levels, the masonry facade of 70 and 72 Seel Street had been exposed to water ingress for so long that it had become unstable: it had to be taken down. Prior to removal, a complete photographic record was taken for future reference, and the gutters, stone lintols and handmade brick features were retained for reuse.

Number 68 had been subjected to fire damage as well as water ingress. The roof members that were supported by the front wall were cut back to the first purlin to allow the condition of the fire-damaged fabric and the extent of timber decay to be assessed from a mobile access platform. Dangerous fabric was removed using man baskets.

2020 Liverpool assessed that the masonry was now capable of being restrained, so the next task was to design an independent facade retention system that could be installed without requiring access within the building. This was done by the company that installed it, RMD Kwikform Engineering. Once 2020 Liverpool had determined the lines of support necessary to maintain the integrity of the wall under vertical dead loads and horizontal wind loads, RMD set about designing the waling (the horizontal shores) and cantilever support frames required to provide the defined support requirements.

The kentledge (the dead-weight required to resist the overturning of the frames) was positioned away from the building to avoid surcharging the basement retaining walls, cellar lights and coal chutes, and the building foundations. The retention system uses horizontal steel waling members positioned against the external and internal faces of the wall, bolted together through structural openings to effectively clamp the wall. Vertical timber packers were used to accommodate differences in alignment along the elevation of the wall. The size of the braced support frames and kentledge were purposely limited so that the projection into the public highway did not necessitate a complete road closure notice or the requirement for any temporary traffic signalling.

64-72 Seel Street: the facade-retention steelwork and its weights (kentledge) had to be installed without access into the existing buildings.

71 Shaw Street: the front elevation with its restraint scaffolding in place

71 SHAW STREET, LIVERPOOL

Dating from c1830, 71 Shaw Street is the last in a long terrace of Regency brick houses and is Grade II listed. The house commands an elevated position on the rise of Everton, which is exposed to the prevailing winds.

Following localised collapse of the masonry walls and internal floors, 2020 Liverpool was requested by the city council’s planning department to advise on the property’s stability. The survey revealed significant bowing and timber lintol failure at each floor level. The central section of the wall was ready to collapse imminently and was losing lateral support from the timber floor and roof construction, which were rotting severely throughout. The condition of the outrigger adjacent to William Henry Street was very poor (although not as poor as the main property), with loose brickwork overhanging the public footpath. Parts of it required demolition or dismantling for safety. Internal inspections revealed that the timber joisted, ground and upper floor construction was on the verge of collapse in several places, particularly to the rear of the property.

The extent of internal collapse and the dangerous condition of the structure necessitated demolition to protect the public and neighbouring properties. However, due to the prominence of the building, its context with the remaining terrace and its listed status, it was agreed that the facade of the property should be retained. A scheme was therefore prepared for a temporary supporting structure and foundations which would allow the remainder of the building to be safely removed.

The load bearing capacity of the arched brick cellar below the public footpath at the front of Number 71 was unknown. Consequently, props were erected inside the cellar to ensure the stability of the facade retention structure. These were positioned directly under the pilasters on either side of the front entrance portico to support the large stone top step and base of each pilaster.

Above ground concrete foundations were formed in the light well and on the public footpath to support the legs of a structural scaffold and to act as kentledge against overturning of the cantilever framework. A structural facade-retention scaffold was erected to the front wall on the public footpath and in the lightwell in front of Number 71. The sandstone parapet along the top of the front elevation was repointed and temporarily restrained with steel straps and resin set dowels.

Site works commenced in March 2006 and were completed by the end of May.

EVALUATION

These two cases studied illustrate the same fundamental problem: the buildings had decayed to the point where safe access was no longer achievable, so none of the interiors could be saved. It is unusual to carry out a facade retention without access to the interior, and the solutions adopted by 2020 Liverpool are subtly different and structurally innovative. In both cases work was completed without entering the buildings, only urgent works were undertaken, and the potential for redevelopment by the owner was not compromised.

The RMD Slimshore solution at Seel Street was chosen because total road closure was not desirable. To confine the works to the footpath and the immediate width of the parking bays, a robust cantilever braced frame was required that could transmit the applied loads safely. The method of restraining the facade was developed to enable additional whaling to be added to the system at a later date if the redevelopment of the buildings required the removal of the party walls. Consideration was also given to the potential length of time the works could be in place. It was anticipated, and subsequently proven, that the owner of the properties would use the opportunity to move his planning application forward. This suggested a short timescale between erection and dismantling. The solution was therefore considered to be technically viable and financially the most cost-effective.

The structural scaffold solution adopted at Shaw Street went through a similar feasibility process. Highway constraints were not as relevant as at Seel Street. Pavement closures and partial road closure could be implemented with traffic management. It was also anticipated that the system would remain in place for an undefined period. Financially, the outright purchase of the scaffold, when installed, was consequently most cost-effective.

These two different approaches have the same outcome: important facades of townscape importance have been retained for the present, whilst permitting future redevelopment. Both will require further investigation and assessment once reconstruction works are commenced, so there is still the potential that further investigations will conclude that the facades cannot be saved. Only time will tell.

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Recommended Reading

M Bussell et al, Retention of Masonry Facades – Best Practice Guide, CIRIA Report C579, 2003
M Bussell et al, Retention of Masonry Facades – Best Practice Site Handbook, CIRIA Report C589, 2003
HSE Guidance Note GS51 Facade Retention, Health & Safety Executive, 1992
Stopping the Rot, English Heritage, London, 1998

This article is reproduced from The Building Conservation Directory, 2008

Author

IAN WEIR is a conservation accredited engineer and a director of 2020 Liverpool.

Further information

Structural