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Posted: Wed Apr 28, 2010 6:34 pm
by LotsOfClay
My garden is about 1.2 metres higher than my neighbours.
See diagram at http://i42.tinypic.com/fdc45l.jpg

The height difference is currently retained by:
a) a buried "retaining wall" made of horizontal sleepers and vertical scaffold poles, of unknown strength.
b) a wooden fence, which is bending under the strain. It's not clear whether this is just due to the soil between it and the sleeper wall, or whether the sleeper wall has also moved.

Originally the garden sloped down to the fence, but a previous owner has levelled the garden with several tonnes of clay, which seems to be a little unstable with some movement.

Ideally I'd like a block retaining wall or similar built fairly close to the boundary, but I'm concerned that the neighbours' tree roots would be damaged. Builders who have come to look at the site seem reluctant to quote, possibly due to the movement and the proximity of the house. Access is also limited.

A structural engineer that I've paid to inspect the site has suggested removing the sleeper/scaffold wall, and regrading the garden to stable angle. Decking would be installed over the resulting excavation.

I've spoken to the neighbours, and they're currently quite relaxed.

Any thoughts on my options?

Given the proximity of the house, what sort of written guarantees should I seek from the enginneer that his plans will not result in further movement or damage to the house?

I'm thinking of carefully excavating between the sleeper wall and the fence, to reduce the load on the fence until the permanent fix, and also allow the sleeper wall to be inspected. Does this sound risky?

The fence is 10 metres long. Any ideas on approximate costs of the various options?

Thanks

Posted: Wed Apr 28, 2010 7:36 pm
by lutonlagerlout
an engineer can easily design a concrete L section beam where the horizontal part extends towards your neighbour to alleviate rotational movement
fair bit of groundworks there by hand and maybe a pump for the concrete and steel works
i would roughly estimate 7-10k +vat
I use a great engineer up this way but he doesn't like working without a site visit
whatever you do ,do not let anyone build you a straight 225mm wall as this will fail faster than a chocolate teapot,its the rotational force that is greatest with retaining structures
cheers LLL

Posted: Thu Apr 29, 2010 5:55 pm
by LotsOfClay
Thanks for the reply.
Most of the builders who have visited have indicated that something more than 225mm-thick wall is needed.

The idea of restoring the slope appeals because it should be less disruptive than digging the footings for a retaining wall.

I'm waiting for the engineer to produce the design.
It has been suggested that a slope angle of about 26 degrees (ie. 1 in 2) would be stable. The top of the slope would be about 4 metres from the house. Does this sound reasonable, given the proximity of the house and the clay soil?

Are there any lowish cost ways of strengthening a slope (geotextiles?) that could be used?

Posted: Thu Apr 29, 2010 6:43 pm
by lutonlagerlout
of course a slope is a cheapish alternative but i know people in luton with sloping gardens and they are basically unusable
another alternative is terracing,a series of say 300mm high walls with steps
but again you wont be playing footy on this type of garden
its all down to safety and budget
cheers LLL

Posted: Fri Apr 30, 2010 4:14 pm
by LotsOfClay
It may be several weeks before a builder can be brought in to fix the problem. Would it be worthwhile for me to carefully excavate between the sleeper wall and the fence?

Would this reduce the chances of the fence failing in the meantime, or do I risk restabilising things further by digging?

Posted: Fri Apr 30, 2010 8:08 pm
by DNgroundworks
id leave it for the professionals, if it isnt going to suddenly collapse, in a dramatic fashion with the risk of serious injury to somebody, it should be fine until someone with the correct knowledge comes to sort it out, sorry i cant look at your diagram/photo - naff internet :)