Connected to it by a footbridge is another islet, Luotsisaari ('Pilot Island'), where a pilot station was based since before the construction of the current lighthouse.

[5] In the early years of the 20th century it was discovered that the tower swayed in strong wind, and was also leaning to one side; consequently, in 1914-1917 a steel and concrete 'girdle' was added to stabilise the structure.

[5][4] The light source is 40 metres (130 ft) above mean sea level.

[4] The building is protected by the Finnish Heritage Agency, meaning that no exterior or interior alterations are allowed, and the technical equipment may not be removed without permission.

[2] Tove Jansson is said to have used Söderskär as a model when writing the lighthouse island of the book Moominpappa at Sea.