Case studies in Cheltenham / Gloucester / Tewkesbury

Three Day Enviro-Raft

The existing house was built with 2m foundations and tree roots were in very close proximity to the proposed two storey side extension. Building Control advised the trench fill foundations to be a minimum depth of 2m along the side trench and stepped up to meet the existing house. A test hole was dug for building control, firm medium clay was found at 450mm depth, with loose fill on top.

The fence and garden shed were removed along with a small storage shed. Stone paving slabs were also removed thus creating an extension slab area of 35m.

A small digger and one-ton dumper were used for ground works. Two skips were sited on the first day for removal of spoil.

Three and a half No. 8 yard skips were used for a reduced dig to 450mm below the existing ground level, then insulation was sited around the perimeter of the raft for frost protection (75mm of insulation at 600mm deep). A small trench,100mm wide, was dug by hand with a fencing shovel, which was 175mm deeper than the reduced dig for the raft.

150mm deep Type one was laid fully compacted, which weighed about 10 ton in total. 1200 Gauge DPM was laid followed by A393 Mesh with a 50mm gap around the perimeter of the gap to protect the steel. 12 sheets of A393 mesh were used, at £48 plus VAT.

60mm High chair spacers were laid on top of the 1200 gauge at 800mm centres to support the A393. Two layers of A393 mesh were laid at the base of the raft with 60mm high chair spacers laid on top of the base layer. Another two layers of A393 mesh were laid at the top of the raft.

35N concrete pump mix was poured , totalling 10 cubic metres of concrete at £73 per cube.

Total saving for client of over £5000 on traditional trench fill foundations

• Only 3.5 skips used as opposed to 8 skips with trench fill foundations and typical oversite
• Only 1 pour of concrete as foundations and oversite are poured at the same time 
• Only 10m3 of concrete as opposed to 22m3
• Only one course of blocks to DPC
• Stage payment in the first week as opposed to week 2 or 3 

ARCHITECTURAL SERVICES 3 DAY ENVIRO-RAFT SAVES TIME, MONEY AND THE PLANET.

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