Leylandii roots

[zovirax]

I have a row of conifers 20 ft in length and 20ft high.They stand some 15ft from a neighbours wall.Is the root structure of leylandii such that we can expect damage to the footings of the wall?

[alan30]

Trees at that distance are unlikely to cause direct damage.  Damage is more likely to be caused by the trees extracting moisture from the soil and, in the case of a shrinkable clay, causing the clay to shrink and the building/wall to move with it.  Damage will therefore depend on soil type and how you manage the trees.  Leylandii are capable of reaching 90ft in height so you can envisage the future problem.  If you are on shrinkable clay then at 15ft distance I would maintain the trees at no more than 10-12ft in height.

[WendyS]

They will certainly take a lot of moisture from the soil.  But at this height and length I suspect the damage they're causing is equally about good relations with your neighbours in terms of the sunlight the  trees eliminate and stopping their enjoyment of seeing sky instead of horrible dense green leaves all year round.  Be a good neighbour and chop them right back.  I'm sure your neighbours will breathe a huge sigh of relief and love you for it.    I would !!