Building a retaining wall next to trees - will it harm them ?

Hello -
I'm planning to have a retaining wall built to hold back about 1 metre height difference between two gardens. I guess the footings will extend about 1 metre below the surface of the "low" garden. There are some trees within 50 cm of the planned location of the wall, their trunk diameters range between about 5cm and 20cm. I don't want to kill or substantially harm the trees.
The builder I'm getting a quote from says he will put lintels into the wall and footings so that roots larger than about 1cm in diameter don't have to be cut. Is this a sensible approach, for the trees and/or the wall?
Thanks
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harm
wall
Just to clarify, the trees are in the lower garden.
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rtreter wrote:

I get the feeling, that the roots will eventually invade and upset things.
I have a back fence and a gate that was put there by the land owner of the land behind me and I have the same problem. Next door had a tree, whose roots have lifted my path, so I can only just squese past the gate now.
Dave
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The point is not how big the trees are but how big they will be when full grown - if they are to be allowed to do so. You could make nice little bays in the wall if you wanted to make features of them. All depends on how you get on with your neighbour really.
S
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Its not a case of harming the trees its the other way round, trees as they grow can push a wall out of line or even over.
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It might be better to build the retaining wall with purpose made dry concrete blocks. When the roots cause any future movement you can always tear it down and do it again. Plenty of info out there just Google for "dry block retaining wall".
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On Fri, 16 Apr 2010 23:27:24 -0700 (PDT), 1501

That's a good idea but they tend to be expensive. Crib walling offers similar benefits but usually at a lower cost. Concrete and timber crib systems are available, and my personal preference is timber.
Alternatively, use gabion baskets filled with stone.
Crib walling: http://www.maccaferri.co.uk/PAGES00213.html http://www.jpconcrete.co.uk/crib_walling.htm
Gabions: http://www.maccaferri.co.uk/PAGES00281.html http://www.enviromeshgabions.com/mass-gravity-retaining-walls
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'Its not a case of harming the trees its the other way round, trees as they grow can push a wall out of line or even over.'
That is not necessarily the case. It is astonishing to me how plants and even trees seem to be able to sense what is next to them and simply incorporate it rather than pushing it out of the way. In the countryside you will see many a fence - even a wooden one - buried deep within trees as they have simply incorporated it as they grew. I have even seen an iron bedstead with thick boughs growing right through it without bending it at all. In cemeteries you often can see gravestones half embedded in tree trunks yet still in place on their graves. And on a slightly different note, it always impresses me when I find mushrooms with grass growing right through them without having been bent 'off course' at all.
I think that generally it is the wind rock, and drought, that weakens walls rather than the trees themselves actually pushing them. Down the road from me was for many years an old oak in the middle of the pavement. The estate maker had made a little circular wall round it, and it served as a handy seat and pleasant feature for many years: modern councils, unfortunately, are chainsaw, strimmer and weedkiller happy, so our trees all end up decapitated, ringbarked, and trying to grow in poisonous, dead, dust - like that it only takes an extra puff of wind and they are over. (Mind you, have you noticed how in American TV series, they all seem to be able to have luxuriant and un 'pruned' street trees - despite their supposedly litigious nature, lucky b's.)
S
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Have you considered using gabions (rock filled mesh baskets)? They can rest on the soil at the lower level, steel staked before filling to restrict lateral movement and no disruption to the roots at all.
1m height and 4m from a building is a very do-able with these.
The only neg I can think of would be having 750mm to 1m of the basket visible on the high side if that would bother you.
--
fred
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Good basic info here: http://www.weld-mesh.com/gabionstandarddesign.html
and here (480kB pdf): http://www.draindepot.co.uk/cms/UploadedFiles/product_pdfs/images/drain%20depot%20gabion.pdf
--
fred
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Already suggested these at 8:08 AM. ;-)
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