St Bride’s Church in London is one of Wren’s churches. Today it is so encased by subsequent development that it took eight weeks to carry the scaffolding along an alley and erect it to the top of the 67m high spire so that stone and conservation specialists Bakers of Danbury could clean and repair the structure.

The tiered spire of St Bride’s Church in London (said to have been the inspiration for what today are considered traditional wedding cakes) is starting to re-emerge above the rooftops in Fleet Street, as the scaffolding that slowly went up around it at the beginning of the year is just as slowly removed.

The church is so encased by other buildings around it that it was not possible to bring a lorry up to the site to deliver the scaffold. Instead, it was delivered to the far end of one of the alleys, next to the news agency Reuters, that lead to the church and each piece had to be brought in by hand. The replacement stonework is being brought on to site along the same route.

And with the top of the spire at St Bride’s being 67m high – second only among London’s churches to St Paul’s – that was a lot of scaffolding.

It took eight weeks to erect the 32 lifts, which use the cornices of the tiers of the ‘wedding cake’ section as the inside leg of the scaffolding. It will take just as long to strike them, each lift gradually being removed as the work finishes from the top down. Bakers of Danbury, who are carrying out the renovation work, intend to vacate the site in November.

We reported in NSS last month on the topping out ceremony at the church after the cleaning and re-gilding of the weathervane at the top of the slender pinnacle. The views from the scaffolding across London are spectacular, especially of St Paul’s, which is less than half-a-mile away at the other end of Ludgate Hill.

Like St Paul’s, St Bride’s was one of the 51 churches rebuilt under the direction of Sir Christopher Wren after the Great Fire of London in 1666. The sites of both churches had long histories as significant sites of worship in London, as was confirmed in 1953 during an archaeological investigation that accompanied the renovation of St Bride’s to repair bomb damage from World War II that had left it roofless and gutted.

The investigations were carried out by archaeologist Professor W F Grimes, who uncovered the foundations of six previous churches on the site. The remains of those walls can be seen today in the crypt.

Bakers of Danbury’s current £620,000 restoration to the tower and spire was not only to repair weathering and the expected effects of the passing of time that has taken place since then, it was also to undo some of the misguided work carried out on the Portland stonework of the structure subsequently.

As on a great many stone structures, work carried out in the 20th century involved hard cementitious repairs. The rusting of ferrous metal cramps, some going back to the original construction work, had also caused stone to lift and crack.

The accelerated decay caused by hard cements trapping moisture in porous stone is now well understood, as is the damage caused by rusting ferrous metal, which can expand to more than twice its original size.

Bakers’ first job was to clean the stonework. A rope access survey had been carried out, but it is not until the stone is clean that the need for some repairs become apparent.

With scaffolding up, various cleaning systems were employed. A Tensid system was used to remove copper staining left by lightning conductors (a new lightning protection system has been installed by Bakers), while superheated water, gentle abrasive cleaning and nebulous sprays were used elsewhere.

With the stone cleaned, it was surveyed again and a photographic record taken by Bakers of all the areas where work was to be carried out.

At some point in the past, the stonework had been repointed with hard cement, which had been used to create strip joints that stuck up from the surface and created junctions between the finely jointed stone of as much as 25mm. This emphasised the joints and created a patchwork on the surface visible from the ground. It is assumed the point was to emphasise the large size of the blocks of stone used to construct the church.

There were nearly 10,000m of pointing to remove and replace using hydraulic lime mortar. There were also hundreds of hard cement mortar repairs that had been made over the years that had to be removed – it took two months just to chip off all the hard cement. In some cases repairs have been made in lime mortar, in others stone indents have been used.

At the top of the tower, at the start of the ‘wedding cake’ tiers of the spire, the edges of which have now been protected by new leadwork installed over copper to create sharp arrises, there are eight 2m tall urns topped with Portland stone flame finials. The parapet walls on which they stand had iron dog cramps in them that had rusted and lifted the urns. This all had be dismantled to remove the rusted iron.

When the urns were dismantled it was discovered there was only one dowel joining the base with the stone above. Apart from that, it was the weight of the stone and mortar that held the urns together. As they have been returned to their rightful positions they have been tied together with 3m long stainless steel dowels from top to bottom.

The urns had, again, been repaired with hard cement. The decay that had resulted meant some of the stone has had to be replaced. As much as possible of the original material has been retained but heavily corroded stone has been cut from the urns and replaced. All the flames have been reproduced.

Below the parapet, the Corinthian capitals of the columns had extensive hard cementitious repairs. Again, some of these repairs have been replaced with indents and others with lime mortar repairs. Two of the capitals on the south-west corner have been completely re-carved. This area takes the full force of winds coming across the Thames that, even on a calm day in winter, are seldom less than 40mph.

The existing stone has been cut back to solid material and a new, ‘U’ shaped capital has been positioned around the original stone.

At the topping out ceremony last month, the architect in charge of the current project, John Smith from Tangram Architects, praised the quality of the work being carried out by Bakers. He said it was “absolutely tremendous” and added: “On behalf of the church and on my own behalf, thank you very, very much.”

• NSS will re-visit the site when the work is finished and will report back on the project then.