Can Wisteria Cause Subsidence?

Wisteria is fundamentally a vigorous, woody vine (a climbing shrub) that can be trained to grow around a property. Its call sign, purple flowing in the springtime, often makes the exterior of a property stand out in any neighbourhood. However, can wisteria cause damage to your property?

This article will answer some frequently asked questions, including whether wisteria can cause subsidence, when and why, plus how to manage the plant and prevent damage to your foundations.

Can I plant wisteria close to my house?

You can plant wisteria close to your house. Its roots generally grow down, and they will likely turn away from and around large obstacles, such as foundations. There are a couple of other factors which should make you think twice about planting wisteria close to your house though.

Will wisteria damage foundations?

Wisteria shouldn't damage strong foundations because its roots grow mostly down, rather than spreading wide. Standard plants will grow up to 3 foot below the ground, but older, mature plants can grow as deep as 10 feet. Generally, they will turn away or grow around solid obstacles, like foundations.

Don't plant wisteria near weak or damaged foundations

If the foundations are weak or damaged, wisteria's strong roots will force their way through, moving loose stone, block or rubble. This will compromise the strength of the foundation and you may end up with a subsidence problem.

Can wisteria be protected under a Tree Protection Order?

Wisteria is fundamentally a vigorous, woody vine (a climbing shrub), not a tree, so it cannot have a Tree Preservation Order.

Does wisteria damage houses?

Wisteria can damage houses built on clay soil

Clay soil is drier than others. Large trees and shrubs can draw the moisture from the soil, causing 'shrinkage' as the clay turns from a dense liquid to dust, and therefore subsidence.

Don't plant wisteria near old pipes or water tanks, septic tank or irrigation systems

Old pipes and water tanks are prone to leakage. The roots of any large plant will reach toward the water source and force their way in through the hole, causing further damage. They may follow the pipe into the house's foundations.

Can I cut my neighbour's Wisteria?

You can prune back the Wisteria of your neighbour if it is encroaching onto your property; however, you can only cut the Wisteria back to the boundary of your property, and any garden clippings are the property of your neighbour.

How can I prevent subsidence caused by wisteria?

As well as making sure any underground pipes are not leaking, proper maintenance of the plant should protect your property and keep the wisteria healthy.

Mindful planting

If you can, plant the wisteria in a large planter, from which the roots cannot escape. You may consider burying a tub so that it still appears to be growing from the ground. Make sure that the structure you plan the wisteria to climb can sustain its weight and, if growing up the side of the house, secure strong supports for the vine. It is likely to rip weak trellis or wire right out of the walls.

Regular pruning

The root system of a plant is relative to the size of the aerial parts. Keeping the vine from growing too big will prevent the roots from growing too big. You can have a mature, established wisteria which is kept limited to the porch for example, and the roots should only extend to a similar size underground.

Your wisteria will need pruning at least once, if not twice a year. Its tendrils are famous for squeezing through windows, doors and under roof tiles. You must cut these back to avoid damage to the property.

Consider the weight of the plant. If it becomes too heavy, it will pull down fences, pergolas and even walls. Cut the vine back and consider removing thick and heavy sections altogether, as it grows.

Repair leaky pipes

The earlier you catch this issue, the easier it is to fix. Keep vigilant for blocked drains around the plant and for unusually high water bills, in case a mains inlet has been compromised. If you suspect your drains are blocked or leaking, arrange a specialist drain survey from one of our excellent RICS surveyors.

You may line leaky drains with a resin soaked liner, or replace them altogether with polypropylene pipes, which are resistant to damage from tree-roots. Your surveyor will recommend the best course of action for your circumstances.

Remain vigilant

Watch for signs of subsidence (especially if you know your house is built in a high clay area) and act quickly. We'll give you a tailored quote for one of our specialist structural engineers to carry out a subsidence survey, if you notice any of the following:

• New cracks forming
• Doors or windows warping or sticking
• Bulging plaster
• Sagging or sloping floors, walls or ceilings
• Slanting porch or chimney
• Lifting paving

Are you buying a house with wisteria?

All home buyers should get a home survey before buying a property, this is especially true if the building has (or had) wisteria or other plants with aggressive root systems. Our RICS surveyors can recognise signs of subsidence and will flag if there is evidence that you need to consult a structural engineer. Subsidence is one of the most expensive defects to remedy, so don't take the risk of buying without a quality RICS house survey.