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tower of london schematic

BUILDING CONSERVATION
Tower of London, New Armouries Staircase 2009

 

Removal of failed cement screed, alignment corrections and replacement with new Portland Whitbed cladding.

A site the size and age of the Tower of London requires constant attention and the latest project there was to refurbish the southern steps of the New Armouries in the south-eastern corner of the Tower’s inner ward using Portland Whitbed limestone.

The New Armouries was built of red brick in 1663-4. It is now the only ordnance storehouse to survive at the Tower, the rest demolished in the 19th century. It is the oldest surviving ordnance building in the country.

The southern steps allow exit from the ground floor of the building to the inner ward. The steps are not part of the original 17th century brickwork but were sympathetically constructed using a similar red brick in the same English bond as the rest of the building. Plans of the Tower dating from the 1680s and 1845 show steps in this position, although pre-cast concrete steps were added in 1933 when the stores were converted to barracks.

In 1947, the New Armouries building was converted into the Armouries Museum and classical Portland stone motifs were added to the doorways. The Portland steps and door embrasure in the main western entranceway date from this period; it is likely that the Portland stone handrail and pier cap on the southern steps were added at this time.


Problem
A cement screed on the southern steps, poor addition to the 1930s concrete steps, had failed: the modern cementitious surface layer over the brick core had deteriorated. The stairs were both uneven and delaminating; they had become unsafe as well as unsightly.

The bottom step was significantly lower at its northern point where it abutted the building than at the other end because it sits on a distinct slope.


Solution
LSC was required to remedy these failings. The screed was removed and new Portland Whitbed cladding of treads and risers was installed. They were fixed using joggles rather than physical fixings and were bedded using NHL 3.5 hydraulic lime mortar, washed sharp sand, fine washed sand and stone dust at a ratio of 1:2:1:0.5.

The misaligned bottom step was remedied by lifting and re-bedding the granite sets at the bottom of the stairs. The work was closely monitored and supervised by the Tower of London Curator to ensure that there was no disturbance to significant archaeology.

It was agreed that the stone, bedding and pointing mortar should be allowed to mellow naturally; no attempt was made to match it to the adjacent pointing of the brickwork in terms of patina.

‘The end result is in keeping with the embellishments made in the 1940s. The work has been carried out to a high standard and significantly enhances the aspect of the site’
(Maintenance Manager Jamie McCarthy)

 

Chronology

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