|Lismore lighthouse, built in 1833 by Robert Stevenson. Image by tr_7 from Pixabay.|
Lighthouses are structures located in or adjacent to navigable waters and are designed to warn passing shipping of the danger from nearby land, reefs and rocky outcrops. During the day, the lighthouse serves as a visual guide for navigation; at night or in poor light, it reveals its position by a flashing beacon located at the top of the structure. Conventional lighthouses are typically tall, slender tower structures, usually circular in plan and tapering towards the beacon at the top. The light from a modern lighthouse can be seen up to 17 miles away.
Due to advances in communications technology in the early part of the 21st century, modern lighthouses may feature an array of signalling equipment, including radio and radar beacons, and sound fog signals (for obscured weather). Lighthouses with such radio aids can also serve as guidance to aircraft and can also be located inland.
One of the earliest lighthouses was the Pharos of Alexandria, Egypt, completed in 247 BC but thought to have been destroyed by an earthquake around 1350 AD. It has been considered one of the wonders of the ancient world. The Romans also built lighthouses, such as those on either side of the English Channel at Dover and Boulogne. The lighthouse was taken to a high art in the 19th century, particularly in the UK which saw many examples built, such as:
- Eddystone, Plymouth (1882), built of granite, height 40m (see below).
- Lismore, Scotland (1833), freestone/limewashed rubble, height 26m.
- Bishop Rock, Scilly Isles, (1858-1887), granite, height 44m.
One of the pioneering examples was by John Smeaton, a civil engineer who in 1759 completed the remodelling of Winstanley’s lighthouse on the Eddystone rocks in the English Channel. Smeaton used hydraulic lime as mortar between granite blocks secured with dovetail joints and marble dowels. Together with the tapered profile, the result was a very stable structure which effectively dissipated wind forces and was to become the prototype for the modern lighthouse, influencing many future engineers.
Masonry has been the predominant building material due to its weight and resistance to weathering, particularly against aggressive coastal environments comprising sea action, ice thrust and wind overturn. Other materials can include concrete, brick, cast iron and steel. Lanterns and fixtures were often made of bronze due to its resistance to corrosion.
Lismore, Scotland (pictured) is a typical 19th century-style lighthouse, with a diameter of 5.8m at the base and walls of 1.4m minimum wall thickness. The masonry is coursed lime-washed rubble, with painted dressings of freestone; the stone is said to have been quarried at Loch Aline nearby. The parapet-walk runs around the light room which is a cast iron superstructure pierced by two rows of square glass panes.
In ancient lighthouses, beacons were created by wood fires burnt in braziers. Coal was used for this purpose up to the end of the 18th century after which animal or vegetable oils were burnt in lamps. At one point, batteries of candles were used, such as in Smeaton’s light. After around 1850, mineral oil was burned in a series of wicks. Around the end of the 19th century, a further advance, involved burners vaporising mineral oil on a mantle, producing an extremely high brilliance light. This would more often than not be channelled through a lens, such as of the Fresnel type, to focus the light. However, the most significant advance was the introduction of high-intensity electric incandescent lamps: these are clean, safe, adaptable, allow accurate focusing of the optical apparatus and provide a readily-varied concentration of candlepower.
The latter can be problematic to construct given the cost and specialist construction techniques required to withstand tides, currents, sea action, ice and the potential for bottom erosion. Offshore stations anchored to the sea bottom are expensive to build and operate. More popular in the US, these are typically steel structures, similar to oil rigs but much smaller, and comprise living quarters, a helicopter deck, machinery area and a tall mast carrying the shipping light, a radio beacon antenna and a warning light for aviation.
When a fixed structure is impracticable, floating buoys (with lights around 7m above the water line) can be used as small warning elements; on a larger scale, lightships (with lights on mastheads) can be permanently moored at the required locations.
 Manual v automated
Throughout history, lighthouses have usually required lighthouse keepers to maintain the beacon and ensure it operates at the right time and in the required manner. However, the advent of Global Positioning Systems (GPS) in the latter part of the 20th century and other improvements in maritime safety have, in many cases, seen the decline of the non-automated lighthouse. Today’s beacons are likely to comprise solar panels and batteries powering a single light mounted on a steel-framed tower.
Because of these advances in navigational systems, some lighthouses have been decommissioned entirely.
 Related articles on Designing Buildings Wiki
- A review of Scotland's historic lighthouses.
- Cardiff tidal lagoon.
- Coastal defences.
- Conserving Cornish harbours.
- Dam construction.
- Matthew Davidson stonemason and civil engineer.
- New architecture of Scotland’s west coast.
- Seashaken Houses: A lighthouse history from Eddystone to Fastnet.
- Thames barrier.
- Tidal lagoon power.
- Waterfronts Revisited: European ports in a historic and global perspective.
A new paper from the Adam Smith Institute argues that the problem with the High Street has been totally misunderstood, saying that we need to reform restrictive planning rules and reject a policy of managed decline to reinvigorate our town centres.
The Whole Life Cost of Energy (WLCoE) calculator – issued by government in BETA form – is intended to help building owners and operators to understand the full financial cost of the energy their buildings use, and welcomes feedback
New research published by Historic England (HE) shows the value of heritage to England’s economy as it contributes to economic prosperity and growth through jobs in the heritage and construction sectors and from tourism.
Investigations have begun into what caused part of Chester’s Roman city wall to collapse during construction work.
Though conservation professionals' skills in understanding, defining and explaining local character and architecture can help inform new residential design.
Over 500 historic places have been added to the National Heritage List for England (NHLE) in 2019 and Historic England (HE) has showcased 21 highlights.
The K2 prototype telephone box situated outside the Royal Academy in London – built as part of the 1924 competition that gave rise to the iconic design and first listed at Grade II in 1986 – has had its listing upgraded to Grade II*.
The second in a series focusses on developing the Asset Information Model (AIM).
Reflecting issues that will be encountered across the IHBC’s June 2020 Brighton School, think tank Centre for Cities argues for High Street success.
City A.M took a tour of the first apartment to be completed within the original grade II*-listed power station with designer Tim Boyd of Michaelis Boyd – which also designed the interiors for Soho House and the Groucho Club – and Battersea Power Station’s UK sales director Georgia Siri.
A conversion of a locomotive hangar into a public library is the first retrofit to win the top prize at the World Architecture Festival (WAF).
New guidance and research includes: Lightning Protection, Church Roof Replacement using Terne-coated SS, the conservation of Fibrous Plaster, and more.