Victor Chirilas, Director of Mainmark Ground Engineering, UK discusses subsidence in heritage buildings and when to seek professional help.
Buildings that have stood for hundreds of years have their own cultural and historical significance, but methods and the materials used in their original construction don’t always stand the test of time and issues of subsidence are one of the most common problems.
What are the issues in remediating heritage buildings?
Historic buildings may require remediation work to maximise life expectancy and preserve their historical significance. Traditionally, these older buildings were constructed with shallow foundations or footings, many just resting on the soil or on layers of loose stones, leaving them vulnerable to subsidence. A building with shallow foundations can move with the ground it sits on, whereas deeper foundations transfer the load further down where the soil typically doesn’t fluctuate as much. Heritage buildings often have issues with water ingress into the foundation soil which can also cause the ground to subside. These factors need to be considered when devising an appropriate remediation plan.
How do you maintain a heritage building?
Many heritage buildings have legal restrictions in place to help preserve the building’s integrity and history, so before undertaking any work, consultation with the relevant authority is recommended. There are however a number of things building owners can do to help prevent structural issues occurring before it’s too late.
An important thing to do is assess the drainage. While it may not be possible to make significant changes, it is essential that proper maintenance is conducted. This includes ensuring drains are free-flowing with no blockages that could cause an overflow, as a consistent flow of water leaking into the soil can saturate the ground and wash away part of the foundations.
Assessing the grounds and gardens around the building is also crucial, as the roots of trees and shrubs can suck moisture from the ground and cause settlement if they are in close proximity to a building. If there is a tree close to the property, make sure it is managed and maintained so that it does not become a problem and when planting new trees ensure that they are not close to a building.
How do you know when an historic building needs specialist work?
Movement in old buildings is normal, but professional help should be sought when this movement is ongoing and begins to threaten the use or safety of the structure.
New cracking is a good indicator here, if there are cracks over 5mm in size that are continuing to grow, then consult with an expert to assess the underlying cause which could be subsidence. They may recommend ground engineers to help strengthen the foundations and stabilise the structure preventing future movement, as well as raise or re-level the building and reduce, or even close the cracks back up.
Can subsidence be repaired under a heritage building?
To an extent all structures can have their foundation ground issues remediated, but with heritage sites the aim is to strengthen the ground and preserve the structure without causing any other damage.
There are typically two options available; traditional concrete underpinning or more modern resin injection methods. At Mainmark, our proprietary Teretek® engineered resin is a two-in-one solution that can improve ground bearing capacity and re-level structures, with minimal intrusion.
The process is likened to key-hole surgery because it is injected through very small tubes into the ground beneath the foundation in a controlled manner, to fill voids and strengthens the ground that has subsided. This can also help raise the building back to level. In cases where more substantial ground strengthening or lift is required, Mainmark’s JOG Computer Controlled Grouting technology is a reliable and accurate solution which can be used in conjunction with Teretek.
As subsidence continues to become one of the biggest problems affecting older buildings in Britain today, it is critical that owners are aware of the advanced solutions now available, helping to effectively repair the ground to ensure the property stands on stable foundations for many more years to come.
For more information about the solutions required to repair the sinking foundations of a heritage building, please contact us on 0800 975 0507 or visit, https://mainmark.co.uk/asset-owners/sectors/public-buildings/
By Victor Chirilas
Victor is one of the Directors at Mainmark UK, with over 10 years’ experience in project management and construction management. Having joined Mainmark in 2009, he has managed projects in Australia, the UK and New Zealand including the remediation of the Christchurch Art Gallery which was shaken by the 2010 and 2011 earthquakes that hit New Zealand’s South Island, the old Bank of New Zealand building in Kaiapoi and Ultima Furniture’s warehouse in the UK.