The use of insulated raft foundations in UK construction is growing due to three major factors.

The first is the ever-tightening thermal requirements of Part L and the positive move of building to Passive standards – in Passive design an insulated raft is the norm.

The second is the cost certainty of a raft foundation compared with traditional footings.  We have all experienced cases where footings need to be deeper than planned, or weather creates collapses and shoring is required.

The third is that a well-designed raft can often remove the need for a piled foundation in suspect soil conditions.  In this country, we often use piles as the automatic solution to soil issues, and it is not always necessary.  In a recent project we were able to completely remove a piling solution which saved the developer a £32,000 piling bill.

GreenRaft has some unique features which create advantage for designers and builders alike.

The first advantage is that we use extruded polystyrene (XPS) rather than the expanded polystyrene (EPS). XPS can offer higher compressive strength and increased moisture resistance.

It also comes in a board format rather than a moulded  block which allows for greater accuracy and adaptability on size.  With the GreenRaft build format there is no “dimensional creep” and getting the exact size and shape required is simple.

GreenRaft also has an in inbuilt over-sail of insulation which replicates the Frost Protected Shallow Foundation used in North America and Scandinavia.  This effectively helps keep the ground underneath to a higher temperature thus further minimising heat transfer.

An upstand can be incorporated which is proving very popular with timber frame and SIPS companies.  This can be extended to incorporate a retaining wall and or a stepped raft on sloping sites,

We can create details on our CNC hot-wire system specific to the structure and the site.   We work with the designers to build exactly what is needed.  So, when we had a designer suggest that a post-tensioned solution might be a worthwhile option for a larger raft, we worked with the PT experts and the engineers to build what we think was the world’s first Post-Tensioned Insulated Raft.  Reductions on concrete and reinforcing steel helped hit the carbon reduction the designers needed.

To talk with us about how we can work with you, call GreenRaft’s Technical Director, Philip Grove on 01392 823300 or email us at info@greenraft.co.uk.