average cost for conservatory base
1. Conservatory Concrete base. Â£94.00 per sq metre (assumes max build up from ground level to base level of 200 mm) Minimum charge Â£650 (Based on a concrete base - 150 mm thick, brick faced and including damp proof membrane).ased on 3660mm x 3350mm Victorian Style Conservatory. (All calculations are based on gross external areas-no deductions for doors or angles). Base cost = 3.66 x 3.35 = 12.26 sq metres-cost 12.26 x Â£94 = Â£1152.44. 600 mm dwarf wall = 3.66 + 3.35 + 3.35 (10.36 metres) x 0.6 m = 6.216 sq metres.