Prevent settlement on new housing projects

Large numbers of new homes being built on low lying land, especially in coastal areas, has lead to growing problem of ground settlement.

The large numbers of new homes being built on low lying land, especially in coastal areas, has lead to a growing problem of ground settlement in certain regions of the country.

Developers in areas such as East Anglia and the South East are finding they need to take extra measures to prevent settlement of roads and gardens on new housing projects.

Landfast (Anglia) identified 7.5 acres of land that was just right for development, close to Great Yarmouth town centre and coast.

Geotechnical investigations indicated that the land was constituted of over 20 metres of alluvial clays and layers of peat - two of the softest materials to build on and potentially every developer's nightmare! Thousands of years ago the area formed part of a huge estuary and the developer's chosen site for 149 new homes was right in the centre of a soft alluvial clay river bed that was reclaimed hundreds of years ago from marshland though an extensive drainage process.

The houses were to be solidly founded on driven piles to the river bed gravels some 20-28 metres down, but the developer faced the huge challenge of ensuring that the roads, paths and gardens on the project were stable and would not begin to settle.

The pressure was on to find a quick and effective solution to enable them to complete the build in the shortest possible time.

Because the development was located below sea level, a flood risk assessment recommended that the ground level should be raised to protect the houses.

Breydon Park in Great Yarmouth was the first housing estate in the UK to use expanded polystyrene for the dual purposes of raising the ground level and addressing the problem of settlement.

Landfast (Anglia) worked closely with Fordham Johns, now part of Scott Wilson, which carried out geotechnical surveys and engineering assessments to determine the solution to the underlying materials at Breydon Park.

Bob Coe, project engineer for Fordham Johns, specified Fillmaster by Vencel Resil to support the road.

Fillmaster, which is manufactured from expanded polystyrene (EPS), was a more attractive option as it meant being able to act quickly rather than having to load the land and wait for a long period for it to settle.

In total, 1500m3 of Fillmaster was supplied, ranging from 300mm to 1m in thickness, depending on the alignment of the road.

Chris Brown of Landfast, explains: "There had been no major construction on the land before, as the problem of settlement is widely recognised in this area".

"Expanded polystyrene made it possible to continue with our building works here and we are absolutely delighted with the results".

"There has been no settlement at all and you would never know the site was built on such soft ground".

Chris Brown continues: "In last Winter's heavy rains, much of the surrounding areas experienced flooding, but our development remained bone dry".

"It is really satisfying to know the site has such a stable structure underneath it that is protecting homes from flood damage".

Adrian Walker, technical sales manager for Vencel Resil, explains: "Fillmaster provided a simple solution to the problem because of its high strength to weight ratio which means it is really effective in addressing the problem of land settlement".

"It is also very easy to handle and does not require heavy lifting equipment".

Adrian continues: "Expanded polystyrene is a tried and trusted fill material that has it has been specified on many civil engineering projects, including motorways and bridges, where stable surfaces are paramount".

"The fact that Fillmaster is now also being widely used to support housing developments is testament to the reliability of the material and how well it has performed in preventing settlement in a number of high profile projects".

"Because of its lightweight properties, Fillmaster is also ideal for use in the construction of steeper gradient structures".

"With the current demands on land usage as part of PPG3, this is a vital benefit for the new generation of fill materials".

Fillmaster is suitable for a wide range of applications from landscaping, through to road construction, retaining walls, rail and bridge embankments and noise bunds.

The product is HCFC-free, non-toxic and fully recyclable.

It also allows for rapid construction as part of Modern Methods of Construction.

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