Extension foundations - mesh for tree roots

15 Jan 2018
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United Kingdom

Any advice/help would be appreciated

I'm digging my own foundations, had the building inspector initial visit to say everything looks ok.

There is a large bush (almost tree like) close to one of the foundation trench corners the inspector pointed out we should put 'mesh' in this corner to reinforce as tree roots could cause problems in future.

He drew a quick diagram which looked like it showed two rows of mesh 20 cm apart (60cm wide trench)

Foundations are 60cm wide, 1 meter deep to support two story extension.

I had a look online to see what sort of rebar mesh would be suitable but it not clear.

His simple drawing looked like two rows of mesh 20cm apart, standing verticle in the trench.

-would it not need any horizontal mesh, only two rows vertically?
- how would these be fixed in place?
-Any suggestions on rebar mesh type/specification?

Any pointers/help would be appreciated...

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Typically the problem with roots is not that they somehow can break foundations so mesh reinforcement is required to resist this, rather the problem is invariably moisture extraction from the ground.

I would not like to guess what pub conversation your BCO got the vertical mesh idea, but BCOs are not designers nor engineers. It seems like a complete waste of time, however as he will be checking the work, he's the one that will pass it or not with mesh in it or not.

And there are literally loads of grades and sizes of mesh. So which one to use?o_O

You may as well drop some cheap chicken wire in for all the good any mesh will do.
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Absolute rubbish, mesh will do nothing to protect the foundation from the influence of the tree.
Ask your building inspector if he's ever read NHBC chapter 4 on building near trees...

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