Monitoring and Precise Levelling
Many of the Monitoring and Precise Levelling projects that Met Consultancy Group (Met) work on are highly sensitive and confidential. We are often contracted by insurance companies or their agents and legal teams to undertake short and long term monitoring exercises on structures or ground that appears to be moving.
The appearance of cracking tends to be the start of a process that can take many years to resolve and our involvement will generally be setting up a network of control points around a site or building from which to observe fixed points or undertake level grids.
Generally, we agree with the parties involved, a timetable for taking measurements which will often depend on how quickly the structure or ground seems to be changing. We may start by taking readings on a weekly basis, then depending on what the observations show this may continue or be extended to monthly, quarterly or possibly yearly readings.
We have also provided daily monitoring of buildings adjacent to demolition and construction sites to provide peace of mind, evidence and early warning of any possible movement. Automatic systems can be set up to offer 24 hour monitoring with remote alarm alerts to the surveyor of any change from the norm.
A large, newly built warehouse developed floor cracking and deformation of the slab and walls. We monitored the floor over 6 months using total station to show lateral and vertical movement, which was considerable. The building had been built over the high wall of an opencast mine and the engineered solution had failed. The building was demolished.
An office development was built on a remediated quarry site where vibro compaction had been used to stabilise the site. Differential settlement was occurring to a number of buildings and was first noticed when a number of cracks were appearing in the structures. Cracks were monitored using tell tales and a rivet and calliper system installed across the cracks. Monitoring points were installed on the walls both internally and externally. The monitoring ball and precise levelling recorded any vertical movement over a period of 8 years. During this time the building dropped by over 300mm in places. Remediation is in process.
Did you know…?
The Financial Ombudsman quotes “Typically, insurers take longer to settle subsidence claims than they do to settle any other type of claim made under buildings policies. A significant reason for this is that, with subsidence claims, identifying the nature of the damage and its cause is far from the end of the investigation. In many ways, it is only the beginning.
Even once the insurer is satisfied that subsidence caused the damage in question, it must then look carefully into how best to resolve the situation. Determining this can, in itself, be a lengthy process and will depend on a number of variables. These include:
• the make-up of the soil underlying the foundations
• the consistency of that make-up
• the nature of the foundations
• the trigger(s) for the movement, and
• (once the situation is clear) the options for repair.
Part of the process may involve a period of “waiting time” while the pattern and rate of movement is monitored. Unless this has been explained, policyholders may become impatient with what appears – to them – to be unwarranted delay on the insurers’ part.”