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GROWING CONCERNS – the key issues for grass reinforcement

With increased demand for grass paving to driveways, access roads and parking for both commercial and domestic applications, there are certain aspects of both ground conditions and utilisation that all building professionals should consider………..

Today’s wide choice of grass paving systems means that builders now have a  wide choice of products, together it seems with an equally wide range of performance and sustainability claims. Without the clear guidelines of an industry standard it could be possible to end up with a product that might be fine in the short term, but will not stand the test of time, and in turn, not achieve any degree of sustainability.

Take for example a car park in daily use; “will the grass cover and then the structure stand up to that sort of regime?” If the application is to slopes “will it function as an armouring layer and will it offer grip?” These are the sort of challenging questions that that should be asked to ensure a correct specification.

FIT FOR PURPOSE

This perhaps leads onto another question, the appropriate use of grass paving. With more than 40 years of industry experience, the Grass Concrete policy is to guide our clients to whichever system is most appropriate to their need be it insitu concrete, pre-cast concrete or plastic systems, including stating the case where we feel there is inappropriate uses for a particular system. 

It's a growing concern to us that plastic systems might be selected in areas where stronger reinforcement with regular trafficking is essential. Grass Concrete supply all varieties of systems; Grasscrete is cast-on site, precast concrete blocks available as Grassblock via builders merchants, Reinforced plastic system includes Grassroad and Grasskerb.

When considering a design there are a few “golden rules” that can help the process if applied as a checklist. “The paving will be rarely used” is a fairly common statement. Think however about the potential for unplanned heavy use such as from refuse and skip vehicles or regularly trafficked areas of a drive way.

WEIGHT LOAD IMPACT 

In most instances ground reinforcement failure often stems from either an inability to accept weight load or an issue of waterlogging causing loss of grass and weakened support; with in some cases each of these problems being evident. 

With a long established history of installations we are uniquely placed to work closely with engineers and architects alike to recommend appropriate systems – sometimes in combination – where certain areas can be effectively maintained with plastic, and other areas more vulnerable to traffic potential are essential for concrete alternatives. 

GROUND CONDITIONS 

Critical to performance will be the below ground conditions. Most circumstances will see a sub-base depth of 150mm as being sufficient, this should however be proportionately increased where CBR values of 4% or less are encountered. Care should also be taken in specifying the type of sub-base, DOT type 3 materials mion but it provides a greater consistency both in grading and in availability.

Given the demands for Sustainable Urban Drainage grass reinforced systems can permeate at up to 90% the rate of natural grass a safe lag time can be achieved. Lag time is beneficial in the prevention of flooding and can be extended by introducing an underlying drainage blanket across the full extent of the paved area. Grasscrete can and does combine with proprietary forms of sub-ground attenuation.

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