Damp: What You Need to Know

Damp is a dirty word – it is not something anyone wants in their home, but living in Cornwall means an element of acceptance due to our unique location and the microclimate that we are blessed with!

Weather and Climate in Cornwall

Being a relatively slim county and being surrounded by water, inevitably leads to a damper atmosphere here in Cornwall. The sea creates a fairly unique microclimate here in Cornwall, and can take some getting used to! It’s important to understand damp, and the different types, causes and remedies for being able to live in such a beautiful part of the UK.

While typically UK towns and cities experience humidity levels of around 60% day to day, Cornwall’s average humidity often exceeds 80% depending on where in the county you are. The more coastal towns in Cornwall are likely to experience higher humidity.

Humidity is not all bad, while statistically we may not get the hottest weather in Cornwall, the increased humidity often makes it feel warmer than it actually is. On the flip side, the higher humidity does mean we experience increased wet periods, with Cornwall receiving anywhere between 1,200 and 1,600mm of rainfall a year

Generally speaking, the climate in Cornwall is milder overall – we get warmer Winters, and cooler Summers. Snow, and even frost, in more coastal towns and villages in Cornwall is extremely rare due to the insulating effect of the sea around the land.

With the increased moisture that we experience in Cornwall, and a generally damp climate, it is important to be aware of the effects of this and the best way to live in such a unique location. Damp, if not managed, can lead to mould and even some forms of rot which obviously is bad news for your house or building, but can also have health implications.

Condensation Mould – not actually damp!

With damp being a known issue in Cornwall, it is important to differentiate between the various types and causes. Condensation damp is common, but easily rectified and treated.

Condensation occurs when hot air meets cold, and results in moisture. If you boil a pan of water, the hot air rises and hits a cold surface leaving condensation, or water droplets on the cooler surface – exactly the same principle applies when you live in Cornwall.

Houses in Cornwall are a mixture of old and new, but older more traditional cottages in Cornwall will be built of solid stone walls, typically granite, with infill of mud or smaller stones. Typically, the walls of cottages in Cornwall can be as thick as two foot thick, and are predominantly cold if not rendered or insulated. When you live in a cottage in Cornwall, like everyone, you will have heating of some kind – and even without radiators, fires or portable heaters, everyday life results in heat from a kettle, and oven through to just your own body heat, it all contributes to warmer air inside the property.

Without ventilation, the warm air created inside a granite cottage will come into contact with the cold external walls of your home, and over time you may see condensation creating some damp, that if not remedied will lead to condensation mould. Very typical causes of condensation mould is washing being dried indoors without some air circulating – the moisture removed from the clothes as part of the drying process has to go somewhere and it enters the warmer air in the house – only to hit the cold surfaces and create some condensation. Very often, bedrooms have condensation damp visible on ceilings – and this can be where warmer air created by bodies in the room rises, and comes in to contact with any colder spots. Corners of ceilings especially suffer, as sometimes roof insulation is absent or thinner in the corners; meaning the surface gets a little cooler.

Rising Damp

Older cottages around Cornwall, built of solid granite, will normally be built with little or no foundations. The thick, solid stone walls sit directly on the ground and do not by default have any kind of damp proof course. As properties are bought and ‘fixed up’ or renovated, typically most home owners look to installl some form of damp proofing.

Modern construction of houses ensures that contact with moisture held in the ground and the air is managed and minimised via specialist materials and insulation. Without a damp proof course in your floors, water or moisture will be absorbed and will begin to affect the materials it comes into contact with. Similarly, the solid stone walls that are sitting on the ground without any barrier, will absorb moisture around them, and that moisture will rise via capillary action through porous materials.

Rising damp can be identified by staining similar to tide marks on a wall, and sometimes the salts present in ground water that is absorbed can crystalize and cause plaster to bubble or flake. Look for rotten floorboards or skirting boards as a sign of damp that is rising. There are obvious solutions to rising damp and a good surveyor will be able to make recommendations based on the property and its location in Cornwall.

Penetrating Damp

Being constructed of solid stone, traditionally built houses and cottages in Cornwall can suffer with penetrating damp for various reasons. Penetrating damp is a little inevitable in granite houses – but by being heated and ventilated in equal measure, the damp does not need to be an issue and can be kept on top of. Very often, people assume that damp needs heat to dry out, and so they crank up their heating and keep their doors and windows shut – see CONDENSATION DAMP earlier on..

While it is an incredibly tough material, granite, like most stones, is porous. It can absorb water and moisture will travel where small cracks in the surface occur. The method of building with granite meant that between the large blocks of granite, most houses in Cornwall have pointing. Originally, this pointing would have been lime-based to enable the pointing to absorb water, but also to allow that water to be released as it dries out. 

The original method was continued for many years, but as time went on people owning the properties in Cornwall needed to maintain and repair the pointing. As materials, fashions and budgets changed through the decades, more and more home owners in Cornwall had their pointing repaired or sometimes replaced with cement – a more “modern” method that was cheaper and deemed to be better.

Cement traps moisture and does not allow any “breathability” as lime does, so any moisture that enters the structure of a building by the cement pointing stays in the material or travels through, and this can exacerbate damp that penetrates. 

The best all-round solution to living happily in Cornwall in a damper atmosphere is to keep your home ventilated and heated – the circulation of air assists in managing the level of moisture in the atmosphere. Typical features of older properties in Cornwall like open fireplaces or chimneys where woodburners have now been installed are ideal for helping. The constant draw of air through a chimney means that air in your property is moving, and this helps reduce damp in a small way. 

Other Causes

When viewing properties online or in person, be sure to look for the obvious causes of any damp you spot or are alerted to. Some likely causes can be rooves that are in need of repair, gutters that are full or failing and sometimes windows that are in poor condition or have been badly installed.

The main thing to remember with damp is that it is unavoidable in such a climate as here in Cornwall, but if you are aware of it, and you take reasonable steps to minimise it, you can easily live with it. Specialist surveys are available for properties that have damp issues to highlight and detail the extent and causes of the damp. To find a chartered surveyor you can visit RICS – Chartered Surveyors or ask your estate agent for a recommended local surveyor and be sure to ask friends or family locally who may be able to recommend one.