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Fir tree close to retaining wall

I have a Douglas fir growing at the back of my garden about 30cm away from a retaining wall. The wall has developed a slight lean and is in need of repointing. It’s not 100% clear but the tree is probably to some extent to blame although I’m afraid I have let the brickwork get into bad condition. The other side of the wall drops about 6ft to an alleyway (about 4 foot of wall is retaining). The fir is approx. 35ft high (having been reduced by ten foot or so earlier this year after neighbours worried that it was swaying too wildly in their direction). 

The brickie says he can repoint the wall with the tree in situ and as I am rather attached to the tree and generally don’t like cutting things down, I am inclined to let him go ahead with this.

My question is this: with the tree reduced in height, is the root system still expanding? If so, then I guess in repointing the wall with the tree still standing I am just delaying the inevitable and should go the whole hog and have the poor tree cut down.

But if the root system is likely to be as big as it will ever be then I’ll keep the tree and strengthen the wall.

Many thanks for any suggestions, advice or stories of similar problems!


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  • Meant to add a pic or two!!

  • owd potterowd potter teapot townPosts: 836
    Hiya,
    Repointing the wall will do nothing to correct any lean, nor will it significantly address any structural weakness that may have developed.
    As you say this is a retaining wall, is it leaning on the outside below what we can see as ground level on the picture, or just the top part that is clear of the ground?



    Just another day at the plant...
  • Hi, the brickie is adamant that the lean is not severe and the wall would be perfectly stable (he's suggesting reducing the height of wall a little as it is unnecessarily high really).
    The lean is more pronounced at the top but does continue below ground level on the other side. 

    Many thanks!
  • owd potterowd potter teapot townPosts: 836
    OK, so if it is also leaning below ground level than chances are the tree may have been instrumental to this.
    Personal choice of course, but for me I wouldn't want to reduce it's height.
    Lovely traditional old brick wall with half round blue coping. Looks much better than next doors rebuilt wall (IMHO).
    However, it does look from the pic that it is leaning quite badly and looks like it may need rebuilding. Maybe the camera angle that is exaggerating it but if that lean continues at same rate below ground level as it appears to above, i'd guess it is 200mm out top to bottom. Put a string over it and measure it.
    It also appears to be built half brick and it is a high wall to be built that way if so, can you tell if it is half brick or one brick thick below ground level?

    Just another day at the plant...
  • Globetrotter222Globetrotter222 Posts: 13
    edited February 2020
    Hi
    Unfortunately, it is half brick but it does have two supporting "columns" (sorry, I don't know the terminology). The brickie suggested lowering by several bricks and relay the original coping on top. I don't think the lean is as much as 200mm - too dark to check now but I did measure it before. If reduced, it definitely wouldn't be.
    I guess you're saying the tree should go either way? :'(
    Cheers!
  • owd potterowd potter teapot townPosts: 836
    Actually no, if you are so fond of it, i'm not saying the tree should go. 
    Removal of a large tree, if close to the house (and looks like it may be close) can cause more damage especially if you are on clay soil? which will heave as the water previously taken up by the tree returns into the ground. So it should be considered thoroughly either way. 
    Lowering the wall and repointing may serve as a temporary fix, but for me I think the wall really needs to be rebuilt anyway, especially so if you wish to keep the tree as a better foundation needs to be installed to prevent any further movement.

    Just another day at the plant...
  • owd potterowd potter teapot townPosts: 836
    of course, if it is swaying then it may need to go for reasons other than destabilising your garden wall.
    Just another day at the plant...
  • I am not sure if I could rebuild with the tree there as I think I would be cutting away roots to make room for the bricks. I'll certainly consider the option. I think the tree is a safe distance from house, but I could be wrong. I'll have another look tomorrow and maybe take some pics.

    Thanks very much for your help and knowledge!!
  • Forester_PeteForester_Pete DevonPosts: 152
    It is worth noting that Douglas fir are vigorous conifers and can get very very big. Taking the top out will not stop the stem expanding steadily and taking the wall with it. I would say the only way of saving the wall long term is to remove the tree. But do take some expert advice.
  • i'd take the tree out, its just been planted in the wrong place,
    the roots are heaving the wall up and away, the only way to stop that is to remove the tree, if you chop the roots the tree will fall away from the wall, which i'm assuming is directly at your house? and relaying the top of the wall won't stop it collapsing, it'll just make the top look straight for a bit.
    on the plus side, looking at the bark and needles it appears to be a Norway spruce, not a Douglas fir
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