Listed Building Repairs For Historic Properties

We love working with listed property owners and supporting them with their listed building repairs; it is our favourite type of work.

But it is a sensitive area and one that requires 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.  

Recently, the Property Care Association (PCA), our trade body, worked alongside RICS and other organisations to create a written methodology regarding surveying historical or period properties in regard to damp defects and building repairs. 

Investigation of Moisture and its Effects in Traditional Buildings

We welcomed this document as it supports how we already work, but it ensures the wider industry can be trained and guided on how to follow this way of surveying.

This methodology is currently a draft and outlines the principles a surveyor should adopt to deliver best practices. 

It is for the “Pre-Purchase” market for advice and consultancy when looking to purchase, so there may be differences to this practice when a surveyor is attending to review a specific issue in part of a building. 

Here are the critical areas of the report to help you understand the approach we will take successfully undertake building repairs on your property. 

Overview of the key pillars 

Stage 1A – Understanding the listed building context

The first requirement is to see the building as a “whole” and take a holistic view. All parts of the building are interlinked and require an assessment that takes account of the full picture. 

It is crucial to consider the age and construction of the building, along with the types of materials and techniques used. This stage also requires a review of the immediate surrounding area, such as pathways, drives, sunken areas, flood areas, elevation, ground levels, drainage, plants, and trees. 

This contextual review will take various temperatures from around the building and focus on high-stress areas, such as those exposed to the elements.

The final aspects to include at this stage are any alterations or additions made. In reviewing any changes to the original building, it is essential to note any newer materials used and how the various areas will be used.

Stage 1B – Understanding The Building: Differences between old and new buildings

Traditional buildings are constructed entirely differently from new buildings. A Surveyor requires knowledge of the various build and construct types, along with an understanding of the various methods and techniques.

The moisture level differences between modern and period properties are vastly different. Similarly, the thermal properties, along with varying occupant levels, can affect the various types of buildings in a very different ways.

Stage 2 – Understanding moisture

To survey a listed building requires the Surveyor to have a clear understanding of 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 and is in addition to the studying of the subject via CPD webinars and formal training courses.

Below is the content of this stage from the document released. As you can see, there is a substantial amount of knowledge required to understand a damp issue in a listed building fully.

Take from:

Historic England and PCA Joint Methodology

  • Demonstrate a clear understanding of the relationships between temperature, relative humidity and 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 be able to determine which methods of moisture measurement 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.

Stage 3 – Understanding moisture-related listed building defects

Different types of buildings have different types of building fabric deterioration issues based on the various construction methods and materials used. 

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
  • Corrosion of metals
  • An infestation of timber affected by moisture
  • The decay of moist timbers
  • 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 – sometimes, there are multiple sources of moisture 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.  

Stage 4 – Diagnosis and Recommendations

Once the survey has been carried out, and all of the above matters have been considered it would 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 in first addressing and stopping the source of moisture along with making changes to ventilation, and airflow, removing materials then monitoring the matter over some time.

Sometimes the first step after gaining consent may be “opening up” works in a small area for a view of what is happening behind.  

The recommendations for the works are all to be in accordance with Heritage Building Regulations and any listed property restrictions. Some works may require listed building consent from the local council.

Any work should have as little impact on the building as possible. The above considerations, as well as legal and regulatory legislation, need to be referred to in regard to any historic building works.