Reduce the environmental impact of your retaining wall
by using gabions instead of brick, block or concrete
Hold up your bank with gabions.
Gabions are a cost-effective and simple way of retaining an
earth bank or stabilising an excavation. There are two basic shapes -
cuboid gabions and their flatter alternative, the Reno Mattress.
Both types of gabion are simply a wire cage filled with large pieces of
natural stone - waste from quarries is ideal (and relatively cheap to
buy although the quarries have now got wise to its value and have put
their prices up accordingly!). When I first started in the construction
business, quarry waste was free to anyone who cared to collect it (just
the job for your rockery) but we had to pay €17 a tonne just for the
material with delivery being an additional €4.50 a tonne. Luckily for
us, our garden is full of large blocks of stone so we just used the
mini-digger for a few hours to move them to the site of the gabions.
Our drive is several hundred metres long and, rather than face every
unwanted traveller spoiling our privacy by turning around directly
outside our house, we created a turning area about 60 metres from the
house by cutting into a steep bank and widening out the other side. This
work had left a 3 metre deep face of soil exposed - something which
could easily slip especially given that the water table can intrude into
this zone. We had a choice of reinforcing it with bricks, blocks,
masonry, concrete or gabions we chose the latter; partly because of cost
but also because of their more aesthetic appearance and also that they
are commonly used here in Umbria.
Despite this local popularity, our builder found it difficult to locate
the bigger gabion cages so we had to resort to trying Builders Merchants
ourselves, eventually selecting one which had a selection of the big 2m
x 2m x 1m cages.
The workmen placed the first row of open gabions at the bottom of the
excavation face and then began to fill them with stone. It is quicker to
place the stone with a digger but it does not make such a tidy nor
strong job. The end result is a bit like dry stone wall wrapped in wire
reinforcement.
When a cage is complete, it is attached by wire to its neighbours and a
new one started. The cages are normally laid in 'stretcher' bond - just
like bricks. Not that gabions are particularly ugly but their
environmental impact can be reduced by planting climbing shrubs which
can cover and take advantage of the wire netting. In a few years all
that will be visible is a flowering, scented retaining wall!
One of the chief advantages of a gabion wall is that there cannot be a
problem with hydrostatic pressure (the effect of water trapped behind
the retaining structure). Since it is made up of 'dry' stones, the water
just passes through it and, in doing so, waters any plants covering its
face.
Good luck with your gabions.
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