Start Point is one of twenty nine towers designed by James Walker. The lighthouse is in the gothic style, topped by a crenellatedparapet. The main tower is built of tarred and white-painted granite ashlar with a cast-iron lantern roofed in copper. The tall circular tower is high with a moulded plinth and pedestal stage and two diminishing stages above that. There are two entrances porches, on the north and south sides. The porch on the south side is blocked and has a 4-centred arch hood mould, whilst the doorway to the north porch has a Tudor arch. Both have raised parapets with Trinity House arms. The inside of the tower includes a cantilevered granite staircase around the inside well of the tower with an ironbalustrade completed by a cast-iron newel. The lighthouse originally had the keepers' living accommodation on the ground and first floors but this was removed in 1871 when new keepers' houses were built, either side of the porches to the north and south. In 1882 another cottage was built, detached from the tower, to the east. All three were designed by James Douglass. Other nearby buildings were used by the lighthouse keepers, who originally could only get on or off the lighthouse by boat, such as the well-house and piggery.
Optics
The original main optic consisted of a rotating octagonal array of eight large Fresnel lenses, topped by seven tiers of concave mirrors. This was the first time Trinity House had installed a dioptric optic in one of their lighthouses; manufactured by Cookson & co. of Newcastle-upon-Tyne, the design was based on the improved dioptric system developed from the work of Augustin Fresnel by Alan Stevenson, engineer to the Northern Lighthouse Board. In 1873, a new lantern was built on top of the tower, designed by James Douglass. In it, a new, more powerful revolving optic was installed, designed by James Timmins Chance: a six-sided symmetrical optic of the first-order, with refracting prisms above and below the central lens elements. At the time its six lens panels were 'the widest in azimuth hitherto constructed, except some of those of Flamborough Head'; the increase in power, compared to the old 45° lenses, was of the order of 3 to 2. Apparatus of the same design were installed the following year in lighthouses at South Stack and Cape Bon. The light was powered by oil until 1959 when it was electrified. At the same time the optic was replaced by a smaller catadioptric lens, made up of two groups of three asymmetrical panels, which produced a group-flashing light characteristic. In 2018 this rotating optic was replaced by a two-tier LED lantern; the old lens was put on display in the adjacent visitor centre. In addition to the main light a fixed red subsidiary light is shone from a window in the tower to mark the Skerries Bank. This was commissioned at the same time as the main light. The original light source was a single Argand lamp backed by a 21-inch reflector; but, following the 1873 upgrade, it instead used light diverted by means of prisms from the rear of the main lamp. Work began on the automation of Start Point Lighthouse in August 1992 and was carried out by LEC Marine at a cost of £82,754. It was completed in early 1993. After automation, the south keepers' cottage was demolished. The station is now monitored and controlled from the Trinity House Operations Control Centre at Harwich in Essex via a telemetry link.
Foghorn
The light alone was found to be inadequate in fog, and a bell was installed in 1862; the machinery was housed in a small building which still stands on the cliff face to the south-east of the lighthouse. It sounded 48 times every minute, the mechanism being driven by a weight which fell in a tube running down the sheer cliff. A siren replaced the bell in 1877;. The fog siren was housed in a circular building, just to the south of the lighthouse, and sounded through a roof-mounted horizontal horn which could be turned in the direction of the prevailing wind. The fog signal was upgraded in 1883 by the installation of a two-tone siren; it now sounded thrice every three minutes. Around the turn of the century new equipment was installed, including a new pair of 5" sirens sounding through a pair of curved vertical copper trumpets. This was in turn replaced by a more powerful 12" siren in 1928, again housed in the same building, sounded from a pair of conical horns housed in a cast-iron turret on the roof. At the same time a pair of Gardnerdiesel engines were provided to drive the air compressors, replacing an earlier set of engines. In 1989, the erosion of the coast caused the fog signal building to collapse. A lot of the area had to be levelled as a result and retaining walls put in place. An electric signal was instead installed on the gallery of the lighthouse. When required the foghorn sounds once every 60 seconds.
