The structural soundness of your new home

Subsidence

This is probably the most familiar problem affecting properties from bungalows to residential blocks. Subsidence occurs where some external force has acted on the foundations and weakened them to the point where there is significant movement, or even collapse, where the building subsides into the void that has been created around the foundations.

One of the chief causes of subsidence occurs in areas where buildings are built on heavy clay soil. Because of the structure of the soil, it can be affected by long spells of dry weather (as is frequently happening in the UK), where the moisture evaporates from the ground, contracting the soil, creating spaces into which the building subsides.

Another common cause is created by the proximity of planted trees and other water-hungry plants, which spread their roots near to or under the foundations, in search for water sources, sucking up the moisture and creating a similar void for subsidence to occur.

Finally, with increasingly heavy rainfall across the country, the flow of water can impact the soil around the foundations washing it away and weakening those areas in which the building stands.

The solutions are relatively straightforward but can be costly. In both cases of these examples, you'll need a structural engineer to recommend a course of action to rectify the problem. Problematic trees will need to be either cut back or removed entirely, for which advice from a tree surgeon might be appropriate (although bear in mind the additional administrative overhead if there is a tree preservation order placed on the plant). However, take note of the next point, too.

Heave

Heave is far less common - and correspondingly less well-known - than subsidence. Essentially, it's the opposite of subsidence with the soil expanding and pushing at the foundations. The result is that the building is driven upwards or outwards, weakening the foundations.

The principal cause of heave is down to the removal of nearby trees. With the plant no longer sucking out the moisture from the soil around the foundations, water collects, expands the earth and creates the phenomenon as it pushes at the structure.

Often, too, leaking drains or water systems under the ground can create exactly the same conditions if left for too long.

Again, a structural engineer will need to be involved to identify the remedy for heave. As with subsidence, the solution will be relatively straightforward but will be expensive.

Sloping floors and sagging roof

A sagging roof is easy to spot by looking at it from the outside. 

Similarly, a sloping floor will also be immediately noticeable as it will be uncomfortable to walk across it, as well as it being visually obvious, and may be a clear piece of evidence of the effects of subsidence.

A roof should be straight and uniform across its length. If it is sagging, you'll notice a bowing across it, usually with several points as you move along the internal timber frames of the roof structure.

You might also notice evidence of leaking either internally in the rooms or down the external walls as the integrity of the roof is forced to split apart, thus letting water through.

The cause of this is often creating too heavy tiles applied for the roof timbers to cope with the sustained weight. Sometimes the roof timbers have shifted and are no longer supported on the external structure of the building.

This is another critical problem that needs the expertise of a structural engineer to assess and make recommendations for any remedial work. As with any serious structural problem, the cause may be straightforward to identify but the remedy is likely to be costly and to take a lot of time to fix.

Bulging or cracking walls

The subtle nature of the problem can make observation of the problem difficult, particularly where the walls are bulging (either inwards or outwards). 

Cracks are more obvious once they appear, and are usually connected to the corners of doors or windows. You might also notice cracks in the chimney stack.

Causes of these types of problem will usually point to a potential issue with either subsidence or heave, but can also be a result of the roof sagging.

Initial evidence of problems with the structure of the walls might start with previously fine windows and doors becoming more difficult to open.

As soon as you notice this is the case, in addition to cracks forming and gradually widening, you should get it checked out immediately as it is indicative of something serious somewhere within the structure.

Poor renovations and DIY

One of the problems with the British obsession with DIY is that some people may decide to tackle jobs which are beyond their skill and capabilities. That is by no means restricted to the amateur - there are professionals who do a slapdash job, too, unfortunately (which is why chasing recommendations and seeing previous work is so important).

Removing a supporting wall (either for the house structure itself or supporting a chimney stack) or attempting to create an open-plan ambience by opening up the rooms by removing part of the wall are significant problems where the correct procedures and supports are not put in place. Inadequate lintels over new windows and doors may also be a source of structural problems, resulting in cracks, subsidence and even collapse.

Again, you'll need a structural engineer to assess any likely problem and employ a qualified professional to remedy the issue as a matter of urgency.

Insect infestation and water damage

There are several species of insect which are wood-boring, including woodworm, termites and deathwatch beetle, all of which are indigenous to the United Kingdom.

The insects create their nests - some using it as a food source, too - by chewing into the wooden support structures in the home, which eventually become weak and create the problems highlighted above with damaged floors and roofs.

You'll need an expert in infestation control to get rid of any such pests, but you'll also need to spend money on fixing the resultant issues the insects have created.

Where there are internal leaks, or insufficient protection externally, including the damp-proof course to protect dampness rising up through the building's structure from the ground, eventually, certain building materials, such as wood, will become rotten and eventually fall apart - again creating some of the symptoms already mentioned.

For such damage, you'll need a timber specialist and probably a structural engineer depending on the severity of problems created. Such remedies are also likely to be costly.

What to do if you are planning to buy a property

If you are proposing to buy a property and identify areas that are causing you concern with the structure of any of the buildings associated with the home, you should highlight anything you've seen to your chartered surveyor so that they may investigate further. 

If you have opted for a RICS Level 2 Survey (or Homebuyers Report) or the more detailed RICS Level 3 Survey, you'll receive their qualified assessment, with a traffic light system that indicates the severity of the problem and the speed at which it needs to be remedied. They will also identify a high-level cost of the repair.

This all means that, once you have received your survey, you can use the information to renegotiate with your seller to help manage some of the cost of remedial work.

Almost certainly, you'll be concerned about value for money and receiving a high quality service for the cheapest surveying options available.