Trees and hedges and houses
Any Questions?

Q. I have two Lleylandii conifers growing one foot away from the house wall, they are about 14ft tall with a trunk at base about 6 to 7 inches in diameter. Do you think they would have damaged foundations and do I need to remove them?

Q.  We have a 25 year old Cherry Laurel Hedge between ourselves and next-door neighbours, about 5 meters away. They are concerned that the roots may be under mining the foundations of their house which is quite old and built on very shallow foundations. My question is what type of root structure does a Laurel have, is a ball type root or a long travelling root?

A.  They're always difficult ones these questions especially when it concerns a potentially expensive liability such as damage to a house.

Laurels are not particularly known for causing problems near to properties and 5m is a fair distance away. The roots could well grow near to your neighbours house as Laurels are large vigorous plants (they can grow to 40 x 40ft given the chance) unless you have a dwarf variety "Otto Luyken" though this is generally not used as hedging.

Any potential damage is more likely through drying out of the soil causing subsidence (followed by "heave" when it rains again) rather than physical damage by the roots themselves of the house masonry and foundations.

Any advice comes with liability and so you'll be unlikely to find anyone who will say "yes it's ok, no problem". If there's a small chance of damage occurring (and in my opinion, from what you've told me, there IS a possibility) then it would not be a good idea to ignore it and hope for the best. If it was your own property that was threatened, you may take a lighter view of the threat (though I doubt it).

What to do? Check your own buildings insurance so that it covers damage to neighbours property by your plants, many policies have this built in but some do not.

You could get an expert in (at cost) to check the situation - taking soil samples near your neighbours house.

You could dig a trench at great effort on your neighbours side to sever the roots.

Keeping the laurels trimmed, you don't say how high they are, will help reduce root spread considerably, but not remove the threat.

The only way to eliminate the problem altogether is of course to remove the hedge.

Q.  I have two mature willow trees in the garden within 20metres of the house. I am just in the process of a garden design project and the contractor is scaring me with advice on felling them because of the risk of subsidence.

A.  Advice? with advice comes responsibility and if the consequences are possible subsidence damage to a house, it will be a rare advisor who will do anything but err on the side of caution.

The usual "safe" distance for willow trees is recommended at 40m, though this covers the worst case scenario with very vigorous trees and the kind of soil that will compound any damage to the maximum effect. Clay soil that is shrinkable and can be sucked dry by the roots is the main problem. It can contract in summer and then swell again in the winter taking the foundations for a roller coaster ride (albeit a small one) in the process, that's where the damage is done.

There are plenty of willow and other trees that grow closer to houses than the recommended distance without mishap, it depends largely on circumstances.

I think you should follow the advice you have been given and fell the trees, it is your choice whether you do or not.

Q. Robinia "Frisia" - I am trying to find out what the root structure is on this tree.  I have one planted within 4 feet of a neighbours house and they are concerned about the footings. Its a mature tree ( some 25ft high) and I want to avoid removing it if the roots don't present a problem.  Have contacted several local garden centres without success.  Any advise appreciated.

Q. There is a 80 ft beech tree in my garden which is 45 ft from the house. Is this a safe distance from the house?

A. I don't think that this is a question you're going to get any-one to answer anything but over-cautiously. With advice of this type goes liability and if the tree fell on the house the liability would be substantial. Beeches are shallow rooted and you've got a large one! Trees do contract disease and can rot and fall, the chances of this happening however is difficult to gauge.

If you're considering whether or not to fell the tree, you have to take into consideration factors such as it's age and health and if it is protected by some preservation order (the chances are that it will be), and how much you like it. You may consider contacting a tree surgeon to take a look first hand, though I have to say if I were that tree surgeon (and I'm not and have never been one) I'd err on the side of caution if advising to leave it or not - out comes the axe.

Q. Should laurel hedging should be kept away from buildings? and if so how far as I have just bought a property with a laurel hedge which is within a couple of feet of the building will the roots start to affect the foundations.

A.  Contrary to popular belief, it's not the roots directly damaging foundations that usually do the damage, but the fact that large shrubs and trees can dry the ground out near buildings, so causing the ground to shrink and swell according to the time of year and water availability. It's this ground movement that causes the damage.

There are always far too many variables to give direct advice, soil type, size of plants, age of building, depth of foundations etc. etc. and no-one will give you any but the most precautionary advice - if in doubt cut down the tree or shrub.

Having said all of this, there are trees and shrubs that can happily co-exist with buildings for many years without problems, it depends on how much of a risk you want to take.

Personally, I'd never plant a large woody plant over 6 feet in height closer than about 12 feet from a building. As you get closer, the size should get smaller with nothing over about 3-4 feet within about 3 feet. This is all arbitrary however and is NOT intended as advice. Even then you need to keep an eye on things - that's usually where non-gardeners go wrong.

The main problem comes when previously regularly clipped and maintained hedges / trees etc. are left to their own devices and so what was safe and appropriate gets 10x or more the foliage and water requirements and so dries the ground out all the quicker.