Climate change risk assessment for historic building owners

The expected impact of climate change on historic buildings

An increasing frequency of low impact events is expected over coming years:

• increased pressure on the capacity of downpipes and other rainwater goods.
• increased potential for water to penetrate into the fabric of buildings; particularly as there will be less opportunity for drying between rainfall events
• conditions that may be conducive to the growth of algae and moss on masonry surfaces and mould growth in adjacent timbers.
• buildings may be exposed to increased thermal stress during hotter drier summers – conditions that can also lead to subsidence, as ground-fill shrinks as it dries.

A increasing but low frequency of high impact events is also is expected over coming years:

• increased flooding where this has occurred before and flooding in areas where this was rare in the past.
• greater frequency of storms with high wind speeds and driven rain.

A climate change risk assessment

The research conducted for the Department by Ulster Architectural Heritage suggests that the risk faced by your building is dependent upon the following five factors:

Type

Understanding why your building is of heritage value is important if you want to understand the risks it faces and make decisions about its future. You will probably have a good idea of this already but a way to find out more is to research the record held by the Department. For 70% of NI we hold a detailed record of listed and unlisted buildings of historic interest. The best way to find this data is to zoom down on your building on our Historic Environment Map Viewer. Click on the square over your building and this will take you to the data we hold.

Key considerations for risk assessment of type:

• is the building protected as a listed building, located in a Conservation Area or protected by any other form of heritage designation?
• is there likely to be archaeology associated with the building or its immediate site?
• if so, ensure that you are clear on any restrictions before contemplating work.

Site

A Key factor to consider in respect of your building is where it is sited and therefore its vulnerability to the expected risks listed above. If it is on an exposed headland, for example, it is likely to be more affected by driving rain. If it is situated at the base of a valley it might be more susceptible to flooding. If it is in a sheltered area it may be more vulnerable to dried out ground. The following resources should be of help as you consider this:

• Flood Risk Map.
• Costal Erosion Risk Map.
• Mean Annual Rainfall Map

Key considerations for site risk assessment:

• what is the level of mean annual rainfall for the location of your building relative to other locations in Northern Ireland?
• is your building on an elevated site or site exposed to south westerly prevailing winds?
• is your building in relative proximity to the coast or a river?
• is your building located within the present day Flood Risk NI boundary for coastal/river/surface water flooding?
• is it located within the projected 2030 boundary for coastal/river/surface water flooding?
• is it on a site that is at risk from erosion or subsidence?

Management

If you think about it, it is clear that buildings that are not well maintained are more vulnerable to the effects of climate change. A rusty tin roof with eroded fixings or a roof with slipping slates is more likely to get blown off in a storm than one that is well maintained. Similarly, gutters with vegetation in them are going to be much less effective than clean ones in coping with a sudden downpour. It is good practice, therefore, to monitor your building in a planned manner and to tackle maintenance issues early. For larger buildings a monitoring and maintenance plan is recommended with a log of actions taken.

Key considerations for maintenance risk assessment:

• what is the occupancy/staffing level of your historic building? Who is tasked with management?
• is a management plan in place?
• how frequently are condition checks carried out?
• what are the monitoring processes?
• what is being done to respond to issues arising with regard to condition?
• are there changes that appear attributable to the impact of climate change impacts that might need closer monitoring in future?

Materials

The ability of building materials to cope with climate change can vary and it is important that you know the risks these present. While historic buildings have survived centuries, climate change brings extra stresses such as moisture penetrating much further than before. Solid stone wall constructed buildings, for example, are generally resilient, depending on their stone type. A mud-wall building will be more vulnerable and will depend much more on a sound roof, good breathable rendering; and the maintenance of a dry and ventilated interior. The following sources can provide you with more information:

• The Stone Database.
• Repair of Historic Buildings
• P35 to 37 of the UAH Climate Change report

Key considerations for materials risk assessment:

• what is the principal material of the walls and roof?
• how might the material characteristics of these building materials affect its resilience to climate change?
• in what ways do different materials respond to environmental stresses and those in particular that might be affected or enhanced by climate change?
• what is the detailing, what are the principal design elements of the details, and relative functionality of each detailed element in helping, or failing, to act to respond to weather events?
• what are the key elements of the building’s surrounding infrastructure i.e. drainage, and how is this performing/or not to direct water away from the building?
• what is the setting of the building? Are trees in close proximity? Might trees be at risk of falling in severe winds, is there a high level of leaf fall from trees in proximity?

Condition

Once the primary materials of your building are understood, your next step is to take a look at key elements of the building and their particular condition in more detail. Moving through key elements including foundations, walls, roof, rainwater goods, windows, doors, and interiors, identify any signs of increased stresses that may be a result of changing environmental and meteorological conditions.

Key considerations for condition risk assessment:

• what is the condition of the primary materials and detailing of your building?
• what is the likelihood that climate change may be affecting your building’s condition?
• why might the condition of your building be presenting evidence of impacts of climate change?

Overall risk assessment

A consideration of all of these factors will give you a better idea of the risks that your building faces in future years. The following template will help you to summarise this information and to guage the overall nature of the risks faced.

• Historic Building Risk Assessment - template

It is important, however, not to rush into expensive mitigation measures on the basis of this assessment. You should consult a competent professional experienced in historic buildings before you take any decisions.

UAH climate change report

You can find out more detail on this approach from the report provided to the Department by the UAH.

• Impacts of Climate Change on the Historic Built Environment a Report and Guide