This Southgate Estates guide provides advice on what to do if you are buying or selling a house that has been affected by structural movement

Speaking from experience…

This guide is written by Southgate Estates Director, Jonathan Newall. As well as running Southgate Estates, Jonathan was previously a mechanical engineer and has developed many properties himself. He currently owns and lives in a house in Exeter that suffered subsidence in the 1980’s and was underpinned at this time.

1. What happened and why…

The very first thing that needs to be considered is what caused the damage and when it occurred. If there is an obvious cause for the movement, then it is going to be possible to assess the risk of it happening again in the future.

Common causes of subsidence include:

Historic mine-workings or unsound sub-soil – This is less common in the Exeter area, but in mining areas, settlement is inevitable as the disused mine-shafts gradually collapse.

Tree root ingress or removal – Tree roots can push the foundations up or if a tree is removed, roots can rot away leaving gaps in the ground under the foundations.

Drain Failures – It is not uncommon for failed drains to allow water to wash the soil away from under the foundations. This seems to be particularly prevalent in the Victorian terraces around the Mount Pleasant and Heavitree areas of Exeter. In these houses, the clay drainpipes often run backwards, along the outside of the foundations, to the kitchen at the back of the property. When they fail, they tend to wash the soil away from the back corner of the house, causing cracking to the rear wall and a dropping of the rear corner of the property.

Lack of Foundations – Some older properties didn’t even have foundations! The more common issues tend to centre around different soil types needing different depths of foundations. There are plenty of houses where the builders have underestimated the required depth of the foundations.

Poor structural design – On the odd occasion, the foundations have simply been overloaded by poor structural design which can lead to localised dropping of parts of a building.

Bombing – In certain areas of Exeter, World War II bombing caused ground movement and houses near to bomb sites may show signs of movement.

Flooding – Many houses, particularly around the lower St Thomas and Haven Banks area, show signs of movement dating back to the 1960’s when this area was under several feet of water.

2. Cure the cause…

If you know the root cause, then you need some assurance that the subsidence won’t progress further. For instance, if a drain has failed and washed some of the soil away, you need to know its been fixed and the problem is unlikely to occur again or have any long-term implications. If the ground around the property is gradually collapsing due to historic mine-workings, then you’re likely to keep getting problems. At the other end of the scale, if the movement was caused by World War II bombing, it’s probably not going to get any worse. Underpinning is the name given to the process of installing new foundations, which are often ‘pinned’ to the existing foundations. If a house has been underpinned properly, then it probably has far better foundations than its surrounding neighbours, so further problems are very unlikely.

However, you need to know that they were inspected by a structural engineer and that they were done to a high standard. After underpinning, it is normal for

there to be a period of monitoring to check that no further movement is occurring. Structural engineers often place tell-tales over cracks, which are little devices that show if a crack is growing. Ask your solicitor to request as much information as possible, including all receipts and reports etc. Timing is also important when it comes to insuring the property.

3. Get it checked…

Ask a structural engineer to take a look. If you are making an offer on the property it could be a condition of the offer that the vendors commission a structural survey to demonstrate the integrity of the building. A structural survey is likely to cost between £300 and £800.

If you would like any recommendations for structural engineers or surveyors, feel free to give us a call for an un-biased view.

4. Investigate insurance…

Due to the cost of rectifying structural issues, insurance companies are very wary about insuring properties that have suffered from structural movement. Our own experience at Southgate Estates indicates that specialist insurance will be required for properties that have suffered from subsidence within the last 25 years, although some companies will offer normal terms on properties that have not moved in recent years.

The current trend with insurance companies is to use call centres and online systems for quotations. Most mainstream insurers will decline insurance whenever there has been any structural movement whatsoever (or indeed anything else that is not absolutely straightforward). However, there still a number of mainstream insurers who have in-house underwriters who will make an informed decision on whether they can offer insurance.

Typically, where a specialist insurer is required, the annual premium is likely to be higher than normal so this may need to be factored into the price you pay for a property. If you are looking to let the property out in the future or there is a potential flood risk too, then make sure you ask your insurers about this before buying. Talk to your estate agent about companies who are likely to be able to help.

Also take note that where historic movement has been flagged up, insurance companies may ask for structural reports and arborist (tree surgeon) reports on nearby trees before offering cover.

5. Safe as houses?

Firstly, if a house has been underpinned or has subsided, this really should be disclosed before your offer is accepted and ideally before any offer is made. If the vendors or agents are trying to hide something, then my advice would be to consider whether you can trust any of the information that is being provided (there’s no point in hiding the history of a property as it will need to be declared on the property information forms).

If a house has subsided, then some things won’t be quite as straight as they should be. If character traits and wonky floors in a property are not your thing, then it might not be the one for you. Have a good look at the property and check that all of the windows and doors open correctly and there are no nasty cracks that haven’t been fixed properly. Ask the vendors if they’ve had any work done to straighten things out or if they’ve had any problems in recent years.

If you have established that the property you are looking at is ‘as safe as houses’, you can insure it and you still want it, then there should be nothing getting in the way of buying it. It is normal for subsided houses to go at very slightly less than the market value, but this will depend on the demand, location, desirability etc.