What is building movement monitoring and do I need it for my project?

What is building movement monitoring?

Building movement occurs for a variety of reasons, such as changes in ground conditions (causing heave or subsidence), thermal movement or works to the adjacent land and buildings. When extensive works are undertaken to a party wall or next to the flank wall of a property, movement can occur whilst the works are undertaken and upon completion when the structures settle.

The settlement may cause minor cracks, but it is important to monitor these in case the movement is greater than anticipated. Movement monitoring can also be used to confirm the movement has ceased and remedial works can then be undertaken.

When is structural movement monitoring required?

In party wall matters, we recommend that movement monitoring is required for more extensive works that could lead to significant damage to an adjoining owner’s property if not assessed immediately.

The purpose of monitoring the movement is to mitigate the risk of causing damage to an adjoining owner’s property and to consequently prevent unnecessary inconvenience to adjoining owners. Local councils often recommend that the risk of ground movement must be adequately addressed. One way to assist in the safeguarding of the adjoining owner’s property is to have movement monitoring throughout the project.

Examples of the type of work, which may require movement monitoring include:

• Demolition
• Cutting away reinforced concrete slab from party wall
• Piling
• Excavation works to form a basement
• Underpinning
• Large engineering projects

How does movement monitoring work?

Movement monitoring involves the installation of reflective targets to specified locations on the structure to be monitored (typically the front, rear and flank walls of the adjoining owner’s property). Movement is then monitored by regularly measuring these targets using an electronic distance measuring instrument.

The accuracy of the movement monitoring is +/- 1mm. The Engineers will agree a reasonable ‘trigger level’ of acceptable movement, with work ceasing on site if movement exceeds this level until the project team and contractor can agree the best course of action to prevent further movement from occurring. If there are significant cracks already present prior to the commencement of works, it may be suitable to measure these cracks individually by installing a tell tale crack monitor.

The cost of this will depend on the size of the project and how long the movement monitoring is required. Typically, we would recommend that monitoring is in place with base readings provided prior to the commencement of work.

Depending on the type of works being undertaken, readings will be measured as frequently as required, maybe as much as once per week and measurements being taken after the completion of the works for a period defined by the project Engineer. If damage has been caused to the adjoining owner’s property, it is prudent ascertain whether the movement has finished or is continuing before advising on remedial options. The more visits required, the more expensive the monitoring will be.

Conclusion

Whilst this may seem like a high cost to the Building Owner, it will ultimately benefit them by preventing extensive remedial costs for repairs to the adjoining owner’s property and possibly fees in resolving a dispute under the Party Wall etc. Act 1996 by assessing the movement before it becomes a serious structural issue