Most old buildings move to some degree during their life, but this movement may not be a problem.
Cracks might not be a cause for concern. As most older houses differ in their construction to modern houses, they can tolerate a degree of movement without any serious problems.
What causes structural movement?
There are many issues that can cause structural movement.
If water has got into the fabric of your home it could cause a form of material decay, such as rotting timbers or crumbling bricks, that could compromise its structural stability.
There are other causes of decay, such as the life expectancy of the material.
Problems can also occur with materials moving at different rates in response to changes in temperature. This can give rise to differential movement and distortion.
Older homes were usually built with simple shallow foundations, or possibly none at all. They can be vulnerable to movement over a long period.
As older houses tend to be more flexible than modern buildings, they can sometimes accommodate movement without any problem but it may cause cracking, distortion and cause doors and windows to stick.
Nearby excavation or basement construction can be a cause of structural problems.
Foundations are vulnerable to settlement caused by leaking drains, water mains or rainwater pipes discharging straight onto the ground.
A building may be particularly susceptible on clay soils especially where large trees are close to the building. However, whether individual trees are the cause of structural movement should be assessed carefully by a qualified professional. They will be able to provide advice on your options especially as trees can provide benefits too. They can add to the value of your home, provide shade, help cool the environment and absorb rainfall, which will be increasingly important as the climate changes.
Structural problems can also occur as a result of alterations that affect the overall stability of the building. Common problems include:
- New additions on different foundation or soil type
- Partly removed chimney breasts
- Removal of walls to open up rooms
- Structural alterations for doorways or windows
- Notching into floor joists to accommodate services
- Overloaded floors (rare in houses)
Often these types of problem can be hidden and require some investigative work.
When to consult a specialist
Movement in old buildings can be seasonal, dictated by temperature changes.
It can also be historic, by which we mean that there is evidence of past movement but there is no movement now. Often distortion of the structure can be part of the character of an older house.
Only when the movement is ongoing and threatens the use or safety of the structure should you be concerned.
The structural stability of an older house is dependent on how it all fits together. If the connections between components like walls, floors and roof structure are unstable or inadequate, then the building is vulnerable to disproportionate damage.
If you suspect the movement is ongoing, then arrange for a structural engineer who is familiar with old buildings to inspect it. But unless the structural stability is in question, when safety margins have been eroded by continual movement, then it is best to leave well alone.