Reducing the Risk of Damage from Party Wall Works

Surveyors appointed under the Act have an obligation to reduce the risk of damage to the adjoining owner’s property as far as reasonably possible but adjoining owners must also take reasonable steps to mitigate damage. If both play their part, any claims should be kept to a minimum.

The surveyors’ obligation is set out in Section 7(1):

A building owner shall not exercise any right conferred on him by this Act in such a manner or at such time as to cause unnecessary inconvenience to any adjoining owner or to any adjoining occupier.

Surveyors should therefore assess the risk of damage from the proposed method when agreeing the award. If some aspect of the work is considered likely to cause damage, reasonably practical alternative methods should be considered.

A straightforward example is “hit and miss” casting of foundations. If the proposed works include trench fill foundations parallel to an adjoining structure and deeper than the base of the foundations to that structure, there is a significant risk that the adjoining structure will move towards the trench. The risk can be eliminated by excavating the trench sequentially in short bays. This ensures that the foundation to the adjoining structure remain restrained through the process. It takes longer to excavate a trench in short bays but as the risk to the adjoining structure is significant, it’s a reasonable obligation for the surveyors to place on the building owner.

Where the works are high risk, such as basement excavation or underpinning a party wall, it’s considered reasonable for the surveyor acting for the building owner to engage an independent advising engineer. In that scenario, the advising engineer assists with reducing the risk of damage. They’ll generally start by asking the engineer who designed the works to provide an opinion on the possible impact on the adjoining property by reference to Table 1. BRE Digest 251.

BRE Digest 251 is a table of crack widths ranging from Category 0 (less than about 0.1mm – no action required) to category 5 (15 to 25mm – structural damage that requires breaking out and replacing sections of walls). Anticipated damage up to Category 1 – 1mm wide cracks – will normally be acceptable with high risk works (although a skilled contractor should be able to reduce that risk further). If more significant damage is anticipated, the advising engineer is likely to request that alternative methods of work are considered.

As I say above, adjoining owners are also expected to mitigate their losses. If there is a reasonable step that could be taken to avoid or reduce the loss, but it is not taken, then the loss (or the full amount of the loss as the case may be) cannot be claimed as damages because the loss was not caused by the original wrong, but by the failure to take the reasonable step.

For example, if a china plate falls off a shelf within the adjoining owner’s property due to vibration but they don’t then temporarily move the remainder of the china, they have failed to take a reasonable step to mitigate their loses. The cost of mitigating steps, which in this example might be putting the china in to storage, can form part of the claim.

This is part of a short series of posts relating to claims under the Act.

If you live in the Cambridgeshire of north Essex area and require advice on a party wall matter, you are welcome to contact the author of this post on 01799 543532 or via email.