Why and how was Plymouth Breakwater built

The reason the breakwater was built to was to shelter 35 ships for the navy, they were worried about Napoleon attacking England and in Plymouth where the navy was kept. But because the main weather were coming from the south-west this made the Sound unsafe in winter for months on end, when gales would stream in from the Atlantic. Cawsand Bay could shelter ships, but was not ideal for resupplying

By the late 1700’s the government decided to build a breakwater.  There were a few different ideas on what to build.


In 1788 the above plan was put to the Government by a Mr Smith, the Master-Attendant at the nearby Royal Dockyard.  This breakwater was attached to Bovisand and would have been easier to build but they thought it would silt up after time and become a mud bank and be able to put ships there.

It was decided to put the breakwater in the middle over a number of already shallow areas (Shovel Rock, Panther Rock, St. Carlos Rocks). This still allowed for 35 ships to be sheltered, and allowed the tides to run freely in and out of Plymouth, keeping the shipping lanes deep    report 2

 There were a number of possible shapes the breakwater could be.

report 3

In 1806, Lord St. Vincent commissioned John Rennie and Joseph Whidbey to plan and build the breakwater to his number 5 idea.

report 4

The order to commence construction was given on 22nd June 1811, and the first stone (7 tons) was dropped on 8th August 1812. They were in a hurry to build the breakwater because they thought the French would attacking very soon and they needed the navy ready.

Pictures of the designs are below, top one is the original design, the one below is the modified one after a number of storms had changed the shape of the front of the breakwater.

report 5

The builders estimated that the cost would be about £1.2million pounds ( it really cost £1.5million). At present day costs that would be £74 million, but it would not cost that much money as labour (which was very cheap then and they used French prisoners of war to get the rock) would cost more. One person we spoke to said it would cost closer to a billion pounds these days.

Below is a copy of the cost estimate

report 6

To start with they used rock from quarries in Oreston (Plymouth), they built 50 special ships to do this. There were no engines in those days, they not invented the steam engine at the start of this, so they had to sail. And to drop the rocks in the right place there was not GPS, so they used compasses and a bit of guessing. W
e tried using compasses and plotting a position, it was not quick and the sailing boats we used moved out of position very quickly

The ships were fitted with railway tracks running the hull. This allowed each „stone‟ to be craned on board and onto a truck, and then „run out‟ over the stern and into the sea when on site. For very important dropping of rocks a crane vessel was used.

report 7

In the quarries they found caverns, in the caves were found remains of rhinoceros, bear, hyena, deer, fox and wolf

report 8 report 9

The quarries are now closed off and they want to build houses in them. There were no cranes in those days so blocks had to be lifted by  ropes, blocks  and man power, moved by carts pulled by ponies, on basic railway tracks, at the start of the quarrying steam railway engines had not been invented, when the breakwater was nearly finished and the steam railway engine had been invented it was easier to move the stone and quicker and cheaper. Below is the amount of stone used each year. It got more each year due to new inventions.


report 10


Some of the people who worked on the breakwater rowed out to work every day. On gig rowing boats, we tried it it was very hard especially with some wind against you. There was a famous tragedy where a group were rowing back from work and a storm caught them turned their boat over and the all died.

report 11 report 12


In the first year 16,000 tons of rock were placed, you could see the first rock by March 1813 By 30th July you could see 66om.

In 1815 they decided to make the breakwater higher by 10ft above the original design level, This was to give ‘greater protection to the Sound”.

In January 1816 a big storm hit Plymouth and the breakwater, it changed the shape of the breakwater at the front

report 13

The front is the left side of the above picture. that side points out to sea

They had made the front steeper, but the storm changed it to this shape. They then changed the shape back to the steeper front. There was another storm in 1824 which changed to the shape above. The builders then left it that way as the sea seemed to want it that way.

Eventually the breakwater was completed in 1840, it is 1560m long. It is 13 metres wide at the top and the bottom is 65 metres. It is in about 10 metres of water.

About four and a half million tons of limestone were brought from the Oreston quarries, and two and a half million cubic feet of granite from Dartmoor for the top.