History of Tower Bridge Podcast: Episode 2

Episode 2: Design and construction of Tower Bridge

David Laird, Education and Marketing Officer at Tower Bridge, talks you through the Design and Construction of Tower Bridge.

Transcript

Thank you for joining me on the second episode of this four-part history series about Tower Bridge. My name is David Laird and I work as an Education and Marketing Officer at Tower Bridge. 

Over each episode:  I will share the history of London's Defining Landmark with you.

Today I will be describing the construction process of Tower Bridge, with following episodes covering, ‘how and who lifts Tower Bridge’ and some of our favourite ‘historic tales of this world-famous river crossing’. If you missed our first episode, the origins and design of Tower Bridge, this can be found at www.towerbridge.org.uk/podcasts.

So we continue from episode one, as we were introduced to the architect of Tower Bridge – Sir Horace Jones. 

Sir Horace was well known in the City of London by the late 19th century. 

Having advanced to the role of City Architect in 1864, his famous works included rehousing the cities markets – as Jones led on the design and build of Smithfield, Leadenhall and Billingsgate Markets. 

In 1877, Jones was asked by the special bridge and subway committee to advise on the viability of each design being submitted for Tower Bridge. But at the same time, he drafted his own.

Now as those of you who have listened to the first podcast will know, the initial design of Tower Bridge was that of an informal competition, with around 50 architects and engineers entering.

However, failure of the bridge and subway committee to choose a winner led to its abandonment  by January of 1876. Having now stepped back from his role as City Architect, Jones would ultimately go on to to lead on Tower Bridge's design.  

Now his initial plan looked different to what we can see today. Initially he intended a curved drawbridge structure hoisted above the Thames by chains.

He would however admit that whilst the design provided an aesthetic and economical answer to the corporation’s brief, it still required significant development from his ‘crude’ concept. 

To develop his design, Jones was assisted by the engineer John Wolfe Barry. The youngest son of Sir Charles Barry, the architect of the Houses of Parliament (Palace of Westminster), John provided some modifications on Jones proposal stating emphasising – “I think this bascule or lifting system of opening the centre span should not lightly be set aside”. 

With several alterations made, including the insistence that girders over the raising bascules be horizontal and not curved – work commenced in April 1886. Initially scheduled to take 4 years to complete, from which Jones and Barry would receive a commission of £30,000. The build took 8 years to complete and ran to a cost of over £1 million. 

Queen Victoria, unavailable to lay the foundation stone, instead delegating to her son Edward Prince of Wales. This was laid on too much pomp and ceremony on 21 June 1886 and is still visible on the north-west approach of Tower Bridge.

Though it would go on to take 8 years to complete the Bridge, the initial 4 would be largely unseen by the people of east London. 

In these initial years, the Bridges construction was conducted underwater, with large caissons being sunk into the mud and rock of the river base. 

To imagine a caisson, think of a cardboard box open top and bottom, with a rigid edge. These were sunk into the mud of the riverbed, with their weight pushing them down into the clay below.

This hazardous work was executed by a crack team of divers working in groups of up to six, this was specialist work, requiring expert knowledge and teamwork to dig and sink the caissons accurately and evenly to the correct depth. 

So, specialist was the work, that diving teams travelled across the country to work numerous different builds, including the Forth Rail Bridge, and could command fees of up to £10 per minute. 

Not bad, when you schedule in a 6 to 9-hour day.

Within four years, the initial piers, on which the two Towers now stand, were visible above the Thames.

Part of the delay was that both piers could not be built at the same time, due to the scaffolding = required and the need to keep a 160 ft waterway available for passing shipping.  

But by  1890, construction of the Towers could be built in earnest. 

Now whilst Tower Bridge may appear to be a stone/castle like structure. These gothic additions are merely an artistic flourish. 

The real structure of Tower Bridge is a solid steel frame partially visible through the windows of Tower Bridge.

This part of the structure would be overseen by a famous steel magnate of the Victorian Era – William Arrol. 

Based in Glasgow the Arrol steelworks in Dalmarnock would provide the superstructure frame of Tower Bridge. 

Not one to be beaten on quality, to make sure the structure fitted together, Tower Bridge was assembled in Glasgow – before being disassembled and brought to London by barge, 5 tons at a time. 

Building two matching bridge-halves in parallel, required accuracy and skill to ensure that as the south, always followed by the north crept upwards, both would eventually meet to spec in the middle. 

This work was undertaken by a team ranging from 80 to well over 800 onsite personal each day. 

Squads of Rivet Boys and Riveters either by hand or using hydraulic machinery oversaw the elevation of the Towers by inserting over 13 million rivets into the steel.

A hard-working team it was said could put in close to 200 rivets per day, paid by the rivet, so the more you put in the better the pay

For the construction of Tower Bridge, this was administered by not just local people, with many navvies and specialist coming down to work from Northumberland and Scotland. 

One man we are slowly learning more about was Keshavji Shamji Budhbhatti – an engineer, who having studied at the University of Bombay, relocated to Kentish Town and attended the Royal Indian Engineering College at Coopers Hill before applying and working on Tower Bridge's construction. 

Whilst the initial foundation and creation of the piers was not without problems, the progress of the superstructure was completed with a greater degree of ease. 

One particular quirk in this part of the build, was the need for the Bascules, the central rising part of Tower Bridge, to be built vertically, for the purposes of passing shipping. 

Now the word bascule derives from the French for 'see-saw' or 'balance'.

By 1892, the walkways, elevated between the north and south Tower were approaching completion. 

These would provide not only a platform for pedestrians to cross, but also house the suspension cable supporting the full length of Tower Bridge. 

The final phase of the Bridges construction was of course the cladding of Cornish granite and Portland stone to the Towers. 

First, it was decided that stone held the clear advantage over an iron casing. Aesthetically as well as the protection it provided from corrosion. 

The masonry work was carried out by Perry&Co, under the guide of Herbert Henry Bartlett. 

Like the steelwork before, this was cut and brought to London by Barge along with 31 million bricks for the interior. 

But by 1894, four years late and over budget, Tower Bridge was finally complete. 

Well folks, that’s the end of our construction of Tower Bridge episode, I will be back again soon to tell you more about the how and who lifts Tower Bridge. Goodbye for now.