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.
Penrhyndeudraeth
Penrhyndeudraeth is a village and community in the Welsh region of Gwynedd. The community is close to the mouth of the River Dwyryd on the A487 virtually 3 miles (4.8 kilometres) eastern of Porthmadog, and also had a population of 2,150 at the 2011 census, raised from 2,031 in 2001. The community consists of Minffordd as well as Portmeirion. According to the 2011 Census, Penrhyndeudraeth is the 19th most Welsh-speaking area in Wales, with roughly 76% of the its residents aged 3 years or older stating that they could talk Welsh. According to the latest Estyn inspection record of the village's primary school, Ysgol Cefn Coch, 79% of pupils originated from residences where Welsh is spoken. In an incident in June 2011, with brand-new English property managers of the Royal Oak bar in Penrhyndeudraeth, customers left the club in anger and were endangered with an airgun after being informed to quit ordering their drinks in Welsh. The pub consequently had an adjustment of monitoring. The Penrhyndeudraeth Children as well as Young People's Chaired Eisteddfod is held every year at the Memorial Hall. The village is residence to the Snowdonia National Park Authority headquarters. There are many language traces of Old Welsh to be discovered in the place names in the Penrhyndeudraeth location, such as "Pont Briwet/ Briwet Bridge (Briwet is cognate with the Breton word "Brued" implying bridge). Remains of old huts can be discovered near Ty 'n y Berllan, which date back to the Bronze Age. Penrhyndeudraeth's Alun 'Sbardun' Huws created a song, Strydoedd Aberstalwm (around "streets of long ago"), in tribute to the village. His popular band Y Tebot Piws likewise recorded their farewell album at Penrhyndeudraeth Memorial Hall in 2011.