A Clients Guide To Monitoring Surveys For Buildings & Structures
In this guide we explain what a monitoring survey is, why they are useful and how they are implemented.
Article By: Tom Ayre
Last Update: October 2019
In this article, we will be explaining monitoring survey services. We know that the subject is often confusing to people outside of the industry, hence the need for this article.
Reading this article will give you a good grounding in important aspects of monitoring surveys. This could potentially help you with:
- Saving money when appointing a monitoring survey company
- Understanding exactly what a monitoring survey is
- Protecting your property / neighbouring property from unfair claims.
Let’s get started.
What is a monitoring survey?
A monitoring survey process is undertaken when there is a requirement to check a building or structure for movement over time. The procedure involves repeatedly surveying fixed locations on a structure at set time intervals.
When movement has occurred this can be reported in 3 dimensions with points moving horizontally and/or vertically. Over the course of a monitoring survey project, a movement profile can be observed with actions being undertaken if movement exceeds certain levels.
Monitoring a wall at a power station
Monitoring survey report.
How is a monitoring survey undertaken?
A monitoring survey always starts with the initial setup of the monitoring targets and local survey control network. The targets are fixed to the structure in the pre-designated locations utilising either glue or drilled screws.
Without a fixed monitoring point to resurvey each time the consistency will be poor or non-existent. Fixed points are installed on to the structure and usually consist of survey prisms or reflective target stickers. When using prisms they are typically secured using screws drilled into walls or using high strength glue.
A local survey control network also needs to be installed. This involves placing survey targets (prisms or reflective survey points) away from the site. These are used by the total station as a way of calculating it’s precise position each time a monitoring survey needs to be undertaken.
A monitoring survey is undertaken using a piece of equipment called a total station. A total station is a high accuracy optical instrument that is used to measure distances and angles. Total stations are usually mounted on tripod legs whereby the operator can look through the lens and record survey points. In some cases, automation is required If so a total station can be left in a safe location and operated remotely.
At each survey interval, the total station has to be set up using the local control network. Once set up accurately, the monitoring survey process can be undertaken. Each monitoring point is precisely surveyed using the total station and recorded to the instrument.
Once this data has been reached the office, it is uploaded to the monitoring survey software which can generate data to illustrate movement (or lack of) over time.
Total station at the beach.
Monitoring survey prism
Monitoring survey reflector
When are monitoring surveys commisioned?
A monitoring survey process is usually undertaken on the advice of a professional such as a Stuctural Engineer or Party Wall Surveyor. If a building or structure is a risk of movement then a monitoring survey is usually commisioned.
Typically monitoring surveys are commisioned when undertaking heavy construction works next to existing buildings. Some examples include:
- Piling works
- Basement excavation
Piling rig in London
How can monitoring survey data be used?
Monitoring surveys are usually presented in report and graph format. The reports will outline movement over time. It’s common to see reports showing movement compared to the previous set of readings as well as the initial set of readings.
Graphs can also be produced to show the movement in a graphical sense. Graphs can help show when movement started occuring.
Movement monitoring surveys are an good way to help prove or disprove that movement within a structure has been undertaken. This can help with future claims either made for or against.
Diligent contractors ensure that they minimise movement as a result of construction however claims from neighbours can still arise.
The movement monitoring reports produced can demonstrate movement or lack of over time. This can be used in counter claim situtions where by neighbours insist that damage has occured.
Another purpose of monitoring surveys is from a safety perspective. If a building is moving during construction works then this can be identified. If a movement exceeds a certain level then this can be flagged. The potential source of the movement can be found and mitigated against prior to any problems that could potentially endanger.
Read More About Our Monitoring Surveys
We monitor structures across London & The South East, read up about our monitoring survey service here.
How to save money on your monitoring surveys?
Saving money when possible whilst undertaking a project is important. Below we explain how this can be done when commissioning a monitoring survey company.
Reduce the amount of targets/locations
When your Structural Engineer or Party Wall Survey is looking to commission a survey they usually don’t consider the company who has to undertake the works. Complicated monitoring survey proposals that require multiple total station setup locations add a lot of complexity and time to a job.
Keeping things simple often have negligible effects on the effectiveness of a monitoring survey and can unlock considerable savings if the following elements are considered:
- Can the survey company easily set up with access to their offsite control network?
- Can we reduce the number of monitoring points?
- Are the monitoring points safe and easy to install?
Increase the monitoring interval
Often a surveying company will quote for a monitoring survey job based on a per-visit basis. A simple way of reducing the overall cost of a monitoring survey is to simply reduce the amount of surveys.
- Can a weekly specification be pushed to a 2 weekly interval?
- Can we do less surveys whilst less intense work is being undertaken on site.
- Is it possible to pause the survey work whilst the site is temporarily shut down?
Check their experience
The experience of your monitoring survey team has the possibility of significantly increasing your costs. An incompetent survey company can incorrectly report results and show general insonsistancies. It is important you check the following aspects of a survey company prior to appointment.
- Experience in undertaking monitoring surveys
- Level of insurance for the works.
- What is and isn’t included in their price.
- Reviews from others (Google, Trustpilot ETC).