Where do you Keep the Damp in your Listed Property?

Many listed property owners will be able to tell you immediately where they keep theirs. Under the stairs, in the corner of the living room, in the kitchen. Whether we like it or not, damp is a feature of older properties to a greater or lesser degree, but there are ways to manage it without spending thousands on ineffective treatments which may make the problem worse.

Damp is the single biggest threat to old buildings. Its abundance is matched by the sheer volume of research, advice, half-truths and products that promise to solve these problems. It can seem impossible to cut through it all to determine what the best course of action is for your house.

It's not a simple subject. Often what appears to be an obvious or plausible source of damp is nothing of the sort. I would be happy to have a chat with you before you commit to any sort of work to manage or mitigate a damp problem. It's also worth having a look at some of the technical notices and guidance from Historic England and the Society for the Protection of Ancient Buildings (SPAB). 

Peeling paint and crumbling plaster are tell tale signs of damp

To a degree, living in an old listed property involves having a certain level of tolerance for damp - a small amount tucked away under the stairs may not be worth addressing. Inevitably some cases do need to be addressed and for these resolving a significant damp problem involves a process of elimination. There are six likely candidates to choose from and the damp may be due to one or more of them:

Poor Ventilation

Older houses were built in an era before modern ventilation and heating standards. This meant they were often quite cold and draughty and so over the years improvements were made through draughtproofing and installing central heating. Perversely, this has caused increased moisture levels indoors (coming from kitchens, bathrooms and simply breathing), which now has less opportunity to escape and can cause condensation to form on walls and windows. Tell tale signs are black mould growth on walls and window bars and signs of rot in timber elements (see also below).

Solid Walls

Unlike modern cavity wall constructions, many older homes have solid walls that can absorb water, leading to damp patches internally. There may be many reasons why damp appears, including inadequate or ineffective drainage, differences between external ground level and internal floor levels and unseen plumbing leaks. One thing is for sure; it is essential to allow any moisture present to escape through evaporation on the internal and external sides of the wall. This means ensuring that brick or stonework is only covered with paint, render or plaster that is water permeable. This means 'no' to cement-based plasters and renders and most masonry paints (it is possible to buy 'breathable' external paints). Lime plaster and render is the traditional material of choice here.

Aging Materials

Materials such as roofing, gutters and windows deteriorate over time, becoming less effective at keeping water out. Of these, guttering is a particularly common issue as it often goes unseen for long periods of time (who goes out when it's raining to check whether their gutter is leaking?) - it's only when we see the tell tale sign of green algae or moss growing in discrete patches on the exterior wall of our home or mould on the inside, that we see that something may be awry. For this reason, it's a good idea to introduce a maintenance schedule for your home to ensure that common problem areas are sorted out before they have time to cause an wider issue.

Rising Damp

The materials used to build the walls of older properties are permeable to water. In certain circumstances, water will be drawn up through permeable material until it is removed by evaporation. The height it rises depends on how well ventilated the wall is and how water permeable it is. It's not uncommon to see cement plaster or render applied to an old wall in an effort to stop the damp, but unfortunately this doesn't solve the issue; it simply moves it elsewhere by encouraging the damp to rise higher or spread out wider. It wasn't until the Victorian era that damp proof courses were routinely included in walls and for modern houses with cavity walls today it is a central design feature. However, for older homes, retrofitting a damp proof course (by injecting a special cream, gel, or liquid into holes that are drilled into the wall) is unlikely to be a cheap or effective solution.

Penetrating Damp

Water working its way through walls, often due to faulty guttering, cracks in external render, or deteriorated brickwork, is another common cause. It's worth considering which part of your property is subject to the prevailing wind - if your home is is situated in an exposed position, then persistent driving rain on a wall can seep through a permeable wall. In instances like this, there is a balance to be struck about how and when to use more water impermeable renders whilst maintaining a building's 'breathability'.

Plumbing leaks

Leaking pipes hidden away under floorboards or in cavities are a common cause of damp. If you see a patch of damp, look for drain covers and drains and trace the route the pipework is likely to take to establish whether further investigation might be needed.

Damp can enter a home through cracked render

Signs of damp

Recognising the signs of damp in your home early can prevent more serious damage. Here a few of the tell tale signs to look out for:

• Musty smell: A persistent musty odour is often the first sign of damp.

• Mould: Black or green mould on walls, ceilings, or around windows.

• Staining and discolouration: Damp patches on walls or ceilings, often brown or yellow in colour.

• Peeling paint or wallpaper: Bubbling or peeling paint and wallpaper.

• Crumbled plaster: Plaster that easily crumbles or falls away from the wall (although this could equally be simply due to the age of the plaster).

Solutions for damp problems

Addressing damp in older houses involves a combination of preventive measures and remedial actions. Here are few of the more common:

1. Improve ventilation: Modern homes have extractor fans routinely installed in areas that produce high levels of moisture - kitchens and bathrooms. Older homes may not have these and it may be worth looking into whether it is a viable option to install them in your home. Installing extractor fans, air bricks, or improving window ventilation can significantly reduce indoor moisture levels. Repair and Maintenance: Regularly check and repair roofs, gutters, and downpipes to prevent water ingress. Repointing deteriorated brickwork and repairing render can also help.

2. Use of dehumidifiers: In particularly damp-prone areas, dehumidifiers can be an effective way to reduce moisture levels. Modern units are energy efficient and some are designed to be left to run 24/7.

3. Interior adjustments: Use 'breathable' paints and materials on external walls to allow moisture to escape, reducing the chance of mould and damp build up.

While damp can be a significant issue in old houses, it is not insurmountable. With proper maintenance, timely repairs, and appropriate preventive measures, you can preserve the charm and integrity of your home's historic character while ensuring a healthy and comfortable living environment. If you want to know more, I've noted a few more detailed articles you might wish to read below.

• Control of Dampness - This explains the nature and causes of dampness together with its diagnosis, control and prevention in buildings predating c.1919.

• The Need for Old Buildings to 'Breathe' - Describes how modern building methods and materials are incompatible with the construction of old buildings.

• Water in Permeable Building Materials - This is quite a technical document, digging into the physics of water movement. If you're quite scientifically minded, this will help you to understand why moisture moves the way it does in the fabric of your home.