Ground condition

[raguvun]

Can anybody advise, how I could establish whether the trees at the back of a garden have a deterimental effect on the foundations of a single storey extension which has foundation 2.6 mtrs deep. The trees are at a distance of 20 mtrs from the extension. Is there an expert I could involve to find if the roots are drying the ground around the foundation area.

[woofgang]

the buildings regs department of your local council should be able to help or point you in the right direction

[pigface]

raguvun,

some trees can have an effect from 20 mtrs away

do you know:

(a) the type of trees

(b) the type of soil (is it clay?)

[sddsddean]

The root system of the average tree extends about 1 1/2 times the height of the tree horizontally (if you see what I mean). Admittedly the roots at the outer edge are very fine, but they all have an effect. The worst sort of trees are conifers. Never plant them in a garden if you have the choice. An average 50 foot conifer needs 100 gallons of water per day. It takes this from the surrounding ground and that is what can lead to subsidence, especially in dry weather.

[woofgang]

yes,but that's not the whole story. If the trees have been there a while, they will have had an effect on the water table and you may have a stable situation. Remove the trees and the water table could rise leading to expansion of the soil in summer and frost heave in winter.

[honkytonkman]

Woofgang is right. I had exactly the same concern.

A neighbour was moaning that my Japanese Trees of Heaven were blocking his satellite reception and would also cause problems to a propoed single storey extension he planned to build.

An inspection by the local council deduced that to remove the tress would cause more damage because the tree's uptake of water from the ground was phenomenal and to remove them would result in 'heave' from waterlogged soil. The council were keen to impose a Preservation Order on the trees to prevent their removal. But before this was in place I had the trees removed as I couldn't take the neighbour's moaning and negative attitude. BUT... on removal I got the neighbour to sign a legally binding statement (with witnesses) that said that should his building suffer from the effects of the higher water table, I was not liable. I now wish I'd kept the trees which were 30 years old and obscured the view of my neighbour's hovel ;)