To ensure that heritage and listed buildings become immovable objects largely immune to the inherent vagaries of time, they need some degree of protection from the irresistible and immortal forces that will hit them on a near-daily basis.
There is no way to stop the wind, the snow and the rain from beating down on your heritage building as they will on every building nearby, but there are ways to avoid or at least slow down the potential damage to historic facades and heritage brickwork.
Part of it will be the result of regular, specialist maintenance, part of it will involve repairing structurally important and protective detailing, other parts will involve how to protect historic materials not designed to survive the test of time.
As well as this, there are the details and elements that help to move water and other damaging elements away from where they can cause the most damage, such as through the use of roofing details that allow water to be collected and shed from the building without causing further damage. building details that accentuate the work the building can already do.
All of this is based on some basic fundamental principles of waterproofing.
Why Can Water Cause So Much Damage To Historic Buildings?
The biggest and most intuitive reason why water can damage historic buildings so much is that from stonework to mortar, most heritage buildings are made from materials that are vulnerable to the elements, especially after centuries of use.
A lot of building stone, such as sandstone used in some parts of Yorkshire, is an exceptionally strong and hard-wearing material, but it is also a porous, sedimentary stone, which means it is vulnerable not only to water ingress but to completely crumbling into dust given enough time and water.
At small levels, this can lead to detailing being eroded away over time, but it can also with enough time affect the structural stability of a building entirely.
As well as this, stonework is held together using lime mortar, which is inherently more porous than cement. This makes it more breathable and reduces the potential for damp to damage stonework from within but also means the mortar may need repointing more often.
Replacing this mortar with cement within the joints would be exceptionally counterproductive, as it would instead of keeping moisture out trap existing moisture within the stone and brickwork, accentuating damage.
Furthermore, particularly violent storms can cause more forceful damage such as cracks in roofing materials, slipped tiles and damage to leadwork.
Finally, over time, water can damage historic stone and bricks in ways other than erosion, such as through staining, freeze-thaw cycle damage and encouraging damp, mould, mould and other conditions that may lead to further damage to stonework.
This can be quite difficult to clean without specialist techniques, given the existing vulnerabilities and age of the materials.
However, there are ways to help protect your building, some of which involve preserving details that are already there, and others involve the subtle addition of authentic, inconspicuous building details that accentuate the work the building can already do.
All of this is based on some basic fundamental principles of waterproofing.
The Core Philosophy Of Water Management
The key to any successful water management strategy, tool or system is that it sheds water in such a way that it is pointed down and away from the building, with the latter direction often prioritised in order to avoid accidental damage from splashback and dripping water.
Drainage is key to a building’s survival, and one of the advantages of working with historic buildings is that the ones that have endured this long have been typically constructed with this in mind, in an example of architectural Darwinism.
Many historic buildings have particularly steep roofs, especially in comparison to historic architecture made in warmer climates with less precipitation. Flat roofing has existed since ancient Mesopotamia, but in rainy climates, the water would simply pool on top and cause significant damage.
Protecting a historical building involves installing, repairing and refining building detail elements that help to channel water along the roof, away from the building and down either to the ground below or into gutters where it can safely be drained away.
Roof copings can also be used to great effect in this regard, allowing water to drip away past gable walls while channelling water back towards the roof.
Similarly, hood mouldings above windows and string courses around buildings can also manage water by allowing it to drip away from the walls along window sills that have drip grooves installed on the underside to stop water from running back onto the masonry. All mortar joints also need to be filled correctly to prevent water from running down the building.
Adding New Drainage Details
Whilst one must always be mindful of adding any additional building details and consult with the appropriate preservation groups to ensure that the character of the building is not affected, adding or upgrading drainage features is by far the most effective way of protecting historic stonework.
This will typically take the form of gutters, drains and downpipes, as well as appropriately installed flashing around potential areas of water ingress to stop water getting into the building.
In most cases, more than one protective layer is involved, and drainage systems are often carefully examined to see which elements are suitable as is, and which need to be repaired, modified or added in order to provide adequate protection for the building.
Generally, with most historic buildings, water will hit the roof, channel towards the gutter systems that collect and carefully be guided off of the roof and towards the ground.
At times when there is a considerable amount of rain, a gutter will tend to overspill on the far side, which keeps the flow of water away from the building itself. This is not an ideal, nor exactly elegant solution, but it is effective during particularly significant downpours.
Most guttering and drainpipes will be largely inconspicuous if not effectively a replacement for the drainage solutions that already existed, and this will not significantly affect the character of the building.
Another option is the use of land drains, which can be beneficial where downpipes are in situ. Downpipes that drain water into the ground next to external walls will cause dampness on the internals of a building, particularly if the ground is covered by impermeable materials.
These downpipes should be connected to land drains, water butts or a soakaway that is far enough away from the property to prevent such issues from manifesting.
Note, however, that damaged or blocked land drains will also cause dampness to appear. If drains are cracked, the water will soak into the ground and this will actually cause movement within a building if it’s left too long. The recommended course of action is to have a drain survey carried out to make sure that all drains are free from blockages and aren’t in need of repairs.
Enhancing Existing Protections
Alongside new drainage details, there are also existing features of the building that have often been effective for centuries in protecting the building from water as long as they are well-maintained, fit for purpose and promptly repaired.
The largest detail is, naturally, the roof itself. Unlike the sedimentary stone primarily used to construct the building, the roof generally is made with slate and other more water-resistant stone materials.
Slate tiles are highly effective at channelling water away as long as the roof is sufficiently pitched, but there is the danger of tiles slipping, falling or cracking, which could create entry points for water.
One of the first jobs should be to check the roof, repair tiles and ensure that other details such as cornices, string courses and copings on the roof and wall are in good condition, as they are part of historic measures to protect the stonework below them.
Ultimately, protecting British architectural heritage from British weather is about careful planning, specialist assistance and taking care not only to protect a building but its character as well.
