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.
Montgomery
Montgomery is a community as well as neighborhood in the Welsh Marches, administratively in the Welsh region of Powys. It is the standard county town of the historic county of Montgomeryshire to which it gives its name. The community centre lies regarding 1 mile (1.6 kilometres) west of the English border. Montgomery Castle was begun in 1223 and its parish church in 1227. Other areas in the community include The Old Bell Museum, the Offa's Dyke Path, the Robber's Grave and also the town wall surface. The big Iron Age hillside ft of Ffridd Faldwyn is sited northwest of the town and west of the Castle. In the 2011 census, the neighborhood of Montgomery had a population of 1,295.