ss wrote:
I am recently re laying some 2 x 3 slabs and replacing some badly laid
concrete with matching slabs, under the concrete there is a network of
roots, mostly fine stuff but a few at a 1cm thickness. What is the
best way to deal with this, ideally one of the weedkillers that will
kill it off and prevent regrowth for as long as possible. The roots
belong to trees/shrubs/ivy which is on the other side of my wall and
the roots have over the years forced their way through onto my land
so I cant attack by spraying the leaves as the shrubs are not my
property.

I've come across this many times...firstly, weedkiller doesn't work on
roots, it has to go in via the leaves, and it doesn't do anything to tree
roots anyway, at least not for many years after the tree is dead.

Best bet is to dig a trench along the wall where the offending plants /
trees are and chop everything off to a depth of a foot or two, then infill
with MOT, also throw a bag of cement in there and mix it up with a spade as
you're spreading it, this will effectively make the wall foundations a bit
more beefed up and hopefully keep the roots away for a decade or two.

Rake over the area you are working on and slice through anything that won't
pull out, then re-lay the slabs as normal