Basement extension near plum tree - advice

19 November, 2019

We are planning an extension to the back of our house, which includes a basement. The back garden is already 1.7m below the ground floor (there is a decking and stairs out the back of our ground floor leading into the garden).

The basement would broadly sit where the decking is now but we would need to dig about 1m down (excluding foundations) to get the ceiling height right for a basement.

There is a purple plum tree which sits about 1m away from the corner of the decking and hence 1m away from where we plan to dig the basement. It’s about 6m tall. Given its position I estimate that about 40% of the expanse of the roots would be growing into the space we intend for the basement.

The question would be how deep is the lateral plane of the bulk of the roots? If most of the root mass is below 1m underground then my research suggests you can build foundations (piles) around the roots with minimal cutting back.

I don’t think we can get rid of the tree completely (it will certainly need pruning as its branches will be interfering with the ground floor extension which will sit on top of the basement), since it’s about 1.5m away from our neighbour’s house.

Does anyone have experience with this sort of thing to indicate what the outcome might be when we get to structural planning?

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United Kingdom
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