Unconsolidated soils on new build sites - clearing up after the builders. - LJN Blog Posts

There have been previous discussions on the LJN referring to that frequent frustration caused to the landscaping teams when confronted with the classic new garden in a building site or similar. Indeed most properties dating from the 1960s to the present day will have problems caused by the often irrational and certainly poor treatment of the garden soil profile by the building contractors and / or landowners.Soils are the most vital element of a successful garden and more often than not can be the cause of many problems both immediate and long term in a garden to plants, lawns and hard landscaping work. In order to ease construction most builders will resort to the easiest option of build - machinery.Whilst the practice of selling off the best top soil has now largely ceased, it is still all too common to arrive on a site where a light sprinkling of top soil has been stretched over the top of a heavily compacted through vehicular usage sub soil base. Or worse still when the top soil laid is often a badly blended mix of sub soil layers and top soil / humus layers which are simply impossible to work with. Erosional problems are caused from the outset and during construction it is common to see heavily silted water flowing from new build sites totally unrestricted, (due to planning restrictions previous to construction development companies are often left unregulated during the build - despite the serious issues for the environment).

photo from womble erosion controlThe actual losses incurred in tackling this mess can mean that landscapers cannot afford to do little more than create an instant tidy up. Thus the real problems become more visible later on and the landscapers get the blame and bad reputation. It is vital therefore for any landscaper to highlight the potential risks to a client.Such problems are not restricted to new developments or to the UK. I have been working on a show garden site in France, on a hillside, the plot has seen considerable activity for 19 years and as a consequence the soils are seriously unconsolidated and are not fit for particular designs. Prior to starting the actual design build over 15 man days were spent in trying to create a decent soils base to work on. There is a in fact a large problem across most of France as the rotovator is used as the sole tool for soil preparation, (as with many larger landscaping outfits carrying out work directly for the development companies in the UK), subsequently in many places this annual activity, (the French garden is still more often a vegetable / fruit growing plot than a permanent feature), has seen loose shallow top soils and a panned surface to lower level soils. Thus it is common after flooding to see whole gardens swept clean of their top soil.It is often that by default the work of a landscaper is the remedy of such poor soils by way of using the best soil stabilisers and erosional controls available - plants. This is of course on top of having to plough through the site removing the obligatory broken breeze blocks and yoghurt pots left in the soils by construction teams.Long term problems can be serious to a home owner, that growing dip in the lawn, the ever changing water flows during adverse weather and the subsiding pathways. These are often blamed on the existence of a tree in the vicinity, when that tree has more than likely been the reason why the problem has taken so long to be seen and is not as bad as it could have been.With increasing desires to maximise a garden for growing vegetables or for increasing it's potential as a external room, these problems need to be addressed particularly when combined with the fact that gardens are a serious equation in larger environmental issues.Where are the codes of conduct for soil protection for the development companies? Where are the regulatory authorities to ensure soils and water courses are protected during build and why is much regulation in place subdued in this respect for development companies after planning? Why has the landscaping industry as a whole allowed this situation to continue for so many years?

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Comments

Pip Howard April 17, 2010 at 9:50pm

It is a nightmare and serious financial blow to sub contractors operating under quotes given without checking the under lying soils, I remember once pulling out over 30 square metres of polythene from one plot, buried between 50cm and a metre depth, this takes some time. A friend once found a really good flask and the tea was still warm!!!
Big Dig Groundworks April 18, 2010 at 9:02am

Last year I was flagging on newbuilds which were association housing and all soft landscaped areas had have min 450mm top soil with treepits 300mm deeper if my memory is right. This is the first time I have seen this on a new build site.
All the private houses I work on that were built in the last 20 years do have all sorts of rubble and plastic buried within the first 200mm of the surface.

Did they keep the flask?? after a good clean.
Lawncare-4u.co.uk April 18, 2010 at 10:57am

my garage foundations are full of old bricks, sandstone, rubble etc . had to dig 9ft on one corner !!

needs a structural surveyor now to submit amendment with steel into concrete to the building inspector/council .......... right mess and trouble . looks like a dump pit. !!