We love working with listed property owners and supporting them with their listed building repairs; it is our favourite type of work.
Our experts are regularly recruited to perform a wide range of damp repairs, as Kent has more listed buildings than any other region in England except for Devon.
But it is a sensitive area requiring all due care and attention. We understand that homeowners have a strong attachment to their property, and it has a special place in the history of the town or village within which it sits.
By their nature, listed buildings use different materials and are subject to strict planning regulations that protect our heritage for future generations. With nearly 18,000 listed buildings spread across Kent, the range of problems we are presented with is vast, and our team have seen it all, perfecting various techniques to solve the property’s dampness issues.
We are passionate about protecting these properties and take our responsibilities in this area very seriously, so we were also pleased and reassured to see that the Property Care Association (PCA), our trade body, worked alongside RICS, Historic England and other organisations to create a written methodology regarding surveying historical or period properties regarding damp defects and building repairs.
Investigation of Moisture and its Effects in Traditional Buildings
While the guide doesn’t cover the full process right through to the completion of the repair, it addresses the important process of survey and identification, generally covering the “Pre-Purchase” market, offering advice and consultancy.
We welcome this document as it not only supports how we already work but also ensures that the wider industry will meet the right standards to protect the listed buildings up and down the country.
So, to help you understand the process of listed building damp repairs, we have pulled together our approach, referencing the PCA guide and how it directs us, ensuring we maintain the highest possible standards, giving you and the relevant authorities peace of mind.
Why are listed buildings susceptible to damp
Now that we understand the background and context of the building, any damp-proof specialist who attends your property must have a firm grasp of how dampness can impact a listed building and the materials used. We know, damp can have a devastating impact on any building, and listed buildings are no different.
Given the nature of the materials used and some of the restrictions around solutions, implementing any kind of building repairs on a listed building can be more challenging. This is why it is vital our team have the knowledge and experience to protect your property.
The Knowledge Required
Stage 2 of the PCS guide suggests that surveying a listed building requires the Surveyor to clearly understand the various forms of dampness and its relationships with various materials.
This knowledge is acquired over many years of surveying different types of properties in need of building repairs, in addition to studying the subject via CPD webinars and formal training courses.
Below is the content of this stage from the document released. As you can see, a substantial amount of knowledge is required to understand a damp issue fully in a listed building.
Take from: Historic England and PCA Joint Methodology
- Demonstrate a clear understanding of the relationships between temperature, relative humidity, absolute moisture content and vapour pressure.
- Consider the three states of water and how water can move in its liquid and gaseous states.
- Understand the difference between porosity and permeability.
- Understand how water enters and moves in porous materials.
- Understand larger-scale moisture movement processes (e.g. rain penetration and hydrological pathways formed by open joints and voids).
- Understand how heating, ventilation and moisture are interrelated.
- Understand and be familiar with the operation of equipment used to identify the presence of moisture in building materials and the air.
- Understand the uses and limitations of this equipment and determine which moisture measurement methods are appropriate for the property.
- Knowledge of the various techniques and types of devices used to locate and measure moisture in the built environment, including, for example:
- Electrical resistance meters
- Capacitance meters
- Hygrometers
- Thermo hygrometers
- Thermometers
- Thermal imaging devices
- Anemometers
- Microwave meters
- Atmospheric data loggers and borescopes
- Understand carbide meters and the process of gravimetric moisture analysis.
- Understand the difference between direct and indirect moisture movement techniques.
- Understand the difference between invasive and non-invasive tests and their implications.
- Understand how to record this information in an unambiguous format that can be understood by the client and be used for diagnosis.
- Be aware of long-term monitoring methods and equipment.
- Be aware that traditional building fabrics may be subject to seasonal fluctuations/cycles.
- Understand typical sources of moisture (external, internal, ground, building services and drains).
- Understand the movement of moisture in buildings and the factors that influence the rate and susceptibility of building elements to the same, including porosity, permeability, vapour pressure, vapour pressure differential, human activity and how these relate to building materials, construction types and internal environments.
- Understand humidity control and the importance of absolute moisture content of the air and relative humidity.
- Have an awareness of the effect that human occupation of a building can have on moisture variables (for example, through washing/showers, drying of wet clothes and cooking).
- Understand how buildings react to temperature changes and what thermal gradients are
Understanding moisture-related listed building defects
The damp that affects listed buildings is the same damp that impacts more modern properties; however, these new builds are built to withstand the effects of water. The various construction methods and materials used in older buildings result in different deterioration issues.
These defects affect different parts of the building and need to be thoroughly reviewed, along with consideration for the following:
- The effect of moisture freezing within porous materials and then defrosting.
- When moisture then dries out, the salts and moulds created, normally as a result of rising damp.
- Corrosion of metals.
- An infestation of timber affected by moisture from woodworm.
- The decay of moist timbers, whether wet or dry rot.
- Ensuring that infestations caused by moisture are active and not historic
- The types of fungus, as some, are very similar in look but affect the building very differently
- How buildings are affected when changes are made
- Recognising the various sources of moisture – including rising damp, penetrating damp and condensation that affect a structure; these all need to be identified so that they can be correctly resolved.
- Ventilation or lack of it is a consideration, as well as heating and insulation positions.
- Understand the reasons for surface mould in buildings.
- Salts and how they move through building materials and affect them.
Listed building damp proof solutions
Once the survey has been carried out and all of the above matters have been considered, it will be time to provide recommendations for the best way to resolve the building repairs.
This is not always a “one-stop” solution – it may require small steps first to address and stop the source of moisture, make changes to ventilation and airflow, remove materials, and then monitor the matter over time.
Damp proofing regulations for listed buildings
Making any alterations to listed buildings is tightly controlled by local authority building regulations and requires permission to make any changes.
Using like-for-like materials to maintain the property is usually permitted without permission (but it is always best to check first).
Any work should have as little impact on the building as possible. However, finding a solution for damp proofing will almost certainly involve altering and adding new materials to the building.
Making these changes without permission from the relevant authorities is a criminal offence. The liability can lie with the person undertaking or authorising the work, so it is better to get the appropriate permission in all cases.
Common damp proofing methods
Once you have acquired the appropriate authorisation and identified the problem, here are a few listed building repairs that can be used to tackle dampness.
Prevention is the best cure
If there is a way to avoid working on the building’s structure, this should be the first approach.
Better ventilation and heat management can reduce the likelihood of condensation, particularly around areas of high moisture content, like the bathroom and the kitchen. So if windows can be opened in summer and a more consistent level of heating can be achieved, then this reduces the temperature imbalance in the property.
Another common issue in listed buildings is the changes made outside around the base of the building, whether that is a new driveway or alterations to the gardens that raise the ground level above the damp-proof course if there is one. This can lead to rising damp, a common complaint when visiting listed buildings.
Returning this to its original levels will help remove the bridge the water uses to move into the wall.
Damp proof course
The alternative to this is repairing or inserting a new damp-proof course (DPC) into the wall. There are damp-proof courses that are in keeping with the traditional nature of the buildings, such as a slate DPC, but all work will be checked and officially approved before it takes place.
Vertical air gap membrane
In some scenarios, we have used a vertical air gap membrane. Given the minimal fixings used, it creates a good balance between preserving the existing building and decoration, providing the right finish while allowing the original structure to remain damage-free.
Waterproof cream
There are also now options to use a waterproof cream that can be applied to the porous brickwork to protect against moisture in the ground. However, we always guard against this and ensure it is officially approved.
Faulty rainwater goods
Finally, again, keeping with the prevention theme, problems are often caused by faulty rainwater goods that allow water to penetrate the brickwork from above. The problem could be a broken downpipe, render cracks, or poorly fitted windows.
Therefore, the obvious solution is repairing the offending issue and the likely damaged decor inside the house. These sorts of repairs should stop the dampness from developing. Still, there will be some investment required internally to repair and replace the existing decor, which may require permission, depending on the severity of the alterations.
Listed building repairs
Given the sheer volume of listed buildings in Kent, we regularly answer the call for listed building repairs.
When you come across dampness in your listed property, it can be a significant concern. There is more to consider than a straightforward repair with different building materials and planning regulations to consider.
So, starting with a full assessment of the situation will give you peace of mind that any solution suggested should solve the problem. While there are a range of fixes you can implement around repairs and ventilation, partnering with an expert is critical if you want to find an appropriate solution.
Choosing the right damp proofing specialist
Making listed building repairs requires the right level of expertise. Not everyone is qualified and fully understands the legal implications. With so many listed buildings in Kent and our many years of experience, the South East Timber and Damp team is well-placed to deal with the damp issues you face.
Find out from our clients how we have supported them and delivered solutions for many problems. If you need support with your property, contact us today, and we will be more than happy to help.