THE MATERIALS THAT MAKE LONDON

A tour about history and some of the materials that made it, and some modern materials viewpoints

This London walking tour is a bit different to the norm.

The information below is a summary overview - more facts and figures are provided on a curated walk.

The Royal Geological Society explains how two layers of rock have played an important role in London’s growth: the porous chalk rock provides a source of groundwater which has been heavily used for industry, and some of London’s drinking water supply today comes from boreholes that bring up water from the chalk ‘aquifer’ beneath. London is  fortunate to sit on a thick layer of clay because clay is an easy material to tunnel through.   

Most of London sits on 60-140m of Gault clay, with a few areas of south-east London on chalk. 

Read a paper on the geology of London here.

How large is London?

Greater London covers approximately 606 square miles / 1,570 square km (over its 32 boroughs).

The City of London “Square Mile” is 1.12 square miles of this area.

How large is London's road network and what is being done to make asphalt sustainable?

London's road network is thought to be approx. 14,790 km (9,200 miles). This includes the main road network which is about 590 km (368 miles). Most of London's traffic, around 30%, uses this main road network, also known as the Transport for London Road Network (TLRN). The City of London has just 42 miles of streets (read why the City has "no roads").

It is estimated that London accounts for about 4% of the nation’s roads.

Asphalt can be made more sustainable through increased recycling of reclaimed asphalt pavement (RAP), innovative warm mix asphalt production, and by incorporating other recycled materials like rubber and steel slag.There are ongoing trials and projects in London using RAP to assess its durability, skid resistance, and suitability for different road types, including a trial on the A40 in West London.

London has also seen the introduction of "rubber roads," utilising recycled tires mixed into asphalt, as seen in Bethnal Green.

Materials the Romans used to build Londinium

London has always imported stone for building. Kentish ragstone was a key material used for construction, especially for walls (including London Wall) and buildings. Also brick and other types of stone for facing and rubble cores. Availability and transport of these materials was key to the scale and complexity of Roman building projects in Londinium.

Before Portland stone became London’s default building stone after the Great Fire of London, Kentish Ragstone was London’s premier building stone for 1500 years. All Roman and Medieval buildings in London have some Kentish Ragstone in them. 

Kentish ragstone is a hard grey limestone in Kent, England, drawn from the geological sequence known as the Hythe Beds of the Lower Greensand. For millennia it has been quarried for use both locally and further afield.

Kentish Rag is key to the 3rd century Roman built London Wall and we know that Roman boats carried it from quarries in Kent to London. 

In 1963 excavations at Blackfriars discovered a Roman boat that had sunk, that was: 

”carrying a cargo of building stone by the rivers Medway and Thames from the Maidstone area of Kent, south-east England, to London.” 

How and when the Romans discovered this stone from Medway, Kent, we may never know but they used vast amounts of it as did future generations.

The Thames and its tributaries played a crucial role in transporting building materials like ragstone to Londinium from quarries on the Medway.

Kentish Ragstone was quarried and transported from the Medway Valley, as evidenced by the remains of a Roman sailing barge carrying ragstone found in the Thames

How much stone was used for London Wall?

One estimate suggests over 80% of the facing of the wall was Kentish ragstone:

• A volume of 35,000 cubic metres (approx. 60,000 tonnes) requiring 1,750 voyages of ships to transport the stone. 
• Another estimate mentions 85,000 tonnes of ragstone being brought into London, requiring 3,000 boatloads.

Medieval and Tudor times

In the medieval and Tudor periods, London houses were built out of four basic materials: stone, timber, bricks and earth.

The main stones used on domestic building-sites were ragstone, chalk and flint. The earliest source of these stones must have been the considerable amount of Roman building rubble littering the early medieval city, or available for the comparatively small labour of digging out old Roman foundations, some of them very substantial.

Tudor construction in London featured a lot of timber framing with infill materials like wattle and daub or brick. Stone was used for grander structures, while timber framing allowed for flexibility and affordability. Steeply pitched roofs, small windows with leaded glass, and decorative elements like oriel windows and elaborate fireplaces were also common.

Oak was the most widespread timber used in buildings and other wooden construction.

Elm was supplied usually in the form of boards to be used for doors, window shutters and floors.

The greater volume of wood must have come downriver from such places as Kingston.

After the Great Fire of London 1666

Portland stone and brick became the materials of choice for its durability and appearance. 

Portland stone is a type of Jurassic limestone, known for its creamy white colour and durability, that is quarried on the Isle of Portland, Dorset, England. It's a popular building material, especially for facades and decorative elements, and is known for its weathering resistance and ability to hold an arris.

At the current rate of extraction, there is enough Portland stone on the Isle of Portland to last for another 1,000 years. While reserves are being depleted, particularly in open-cast quarries, companies like Portland Stone Firms and Albion Stone are switching to underground mining to prolong the lifespan of their operations.

London bricks are commonly used across the city. Stock bricks were important for Georgian London.

Bricks were also important to the Victorian era.

To the modern day - reusing materials (part of the circular economy)

Many different materials are used in modern day construction in London.

With a growing interest in steel recovery and reuse, and an appreciation of its potential to deliver substantial embodied carbon savings, there is a need for the industry to develop and share good practice in this area.

City Place House, London, is a current project in which an existing building is being deconstructed to allow reclamation of structural steelwork for use on several new projects in London.

A few stats about some iconic buildings in the City

(information obtained from the Internet)

The Gherkin 

10,000 tonnes of steel use in its construction.

The basement consists of 10,000 meters of Lignacite concrete blocks. 

Concrete foundations are 11 meters deep and are supported by 1,000 steel piles. 

external cladding 24,000 triangular panels of glass.

The Lloyd's Building 

30,000 square meters of stainless steel cladding 

12,000 square meters of glass 

33,510 cubic meters of concrete

The Cheesegrater

18,500 tonnes of steel 

70,000 square meters of glass 

The Walkie Talkie

28,000 cubic meters of concrete 

13,000 tonnes of steel  

33,000 square meters of glass 

The Shard

50,000 cubic meters of concrete 

12,500 tonnes of steel 

11,000 glass panels 

 How many street lamps are there in London?

There are approx. 350,000 in the London Boroughs, TfL, and for the Metropolitan Police. 

The City of London Corporation maintains over 12,000 lighting points, including floodlights, signs, and bollards.

London streetlamps were traditionally made of cast iron for the posts and lanterns, with some modern versions using stainless steel or aluminium.