It depends on the size and type of extension. Small porches or flat roof extensions are very reasonably priced. More substantial two storey extensions can be expensive. In general, the price is roughly proportional to the amount of space you add to your home.
Calstock
Calstock is a civil parish as well as a huge town in south east Cornwall, England, UK, on the border with Devon. The village is located on the River Tamar 6 miles (9.7 kilometres) south west of Tavistock and also 10 miles (16 kilometres) north of Plymouth. The parish had a population of 6,095 in the 2001 census. This had boosted to 6,431 at the 2011 census. The parish encompasses 5,760 acres (23.3 km2) of land, 70 acres (0.28 km2) of water, as well as 44 acres (0.18 km2) of the tidal Tamar. Ashburton Hotel as well as Danescombe Quay neglecting the River Tamar In addition to Calstock, other settlements in the church include Albaston, Chilsworthy, Gunnislake, Harrowbarrow, Latchley, Metherell, Coxpark, Dimson, Drakewalls, Norris Green, Rising Sun and St Ann's Chapel. Calstock town is within the Tamar Valley AONB, is ignored by Cotehele home as well as yards, and pushes the scenic Tamar Valley train. Calstock train station opened on 2 March 1908. The town is twinned with Saint-Thuriau in Brittany, France.