Understanding the Causes and Effects of Rising Damp in Older Buildings

4 Sep 2023
Older buildings, though brimming with character and charm, often come with a unique set of challenges. One such challenge, encountered frequently in older homes in the UK, is rising damp. It’s crucial to understand its causes and effects to ensure the longevity and safety of these historic structures. By the end of this guide, you should have a comprehensive understanding of what causes rising damp in older buildings and the impact it can have.

What is Rising Damp?

First, let’s first define rising damp. This phenomenon, particularly prevalent in older buildings, is of concern to many property owners. Rising damp is a process where moisture from the ground travels upwards through the walls of a building by capillary action. Think of the walls as a sponge, soaking water from the ground. This moisture can climb to a height of one metre or even more, depending on the building materials and conditions. Several tell-tale signs can indicate the presence of rising damp, including:
  • Tide marks: You may notice a visible ‘tide mark’ on the lower section of affected walls on the ground floor. This mark differentiates the damp area below it from the dry section above.
  • Damaged décor: Peeling paint, decaying wallpaper, and the degradation of plaster are common manifestations.
  • Salt deposits: As moisture rises, it brings ground salts with it. When the moisture evaporates, these salts remain on the surface, creating white, powdery deposits.
  • Musty smell: Affected areas often exude a damp and musty odour, especially in poorly ventilated rooms.

The Root Causes of Rising Damp

Before jumping into solutions, it’s essential to understand where rising damp comes from. The root causes of rising damp in older buildings are often multifaceted. While some can be attributed to the architectural practices of the past, others are a result of environmental shifts or simple wear and tear.

Absence of a Damp-Proof Course (DPC)

In the past, many builders didn’t use the preventative measures we have today. The concept of a damp proof course, or DPC, which acts as a barrier against upward moisture migration, was either not introduced or was in its nascent stage. In some instances, older buildings were constructed with some form of a DPC. However, being made of slate or other materials, these DPCs have often decayed or become ineffective over time. It’s important to remember that in the past, even if a building had a DPC, the methods used back then were not as advanced as today’s solutions, making them less efficient in the long run.

Deterioration Over Time

All materials have a lifespan. As years turn into decades and centuries, even the sturdiest of stones or bricks can become porous, allowing moisture to seep through. Plus, climate changes, harsh weather conditions, or even nearby vegetation can influence the rate of deterioration, accelerating the process in some cases.

Faulty External Ground Levels

Over the years, a building's exterior may have been modified. A garden might be turned into a pathway, for example, or the ground may have been elevated for some other purpose. When the ground level is higher externally, it can lead to water pooling against the base of the building. This stagnant water finds its way into the building’s fabric, causing dampness.

Defective Plumbing

Older plumbing systems, made of materials like lead or steel, can corrode or deteriorate, leading to subtle leaks that contribute to dampness. As construction techniques evolved over time, older buildings might have had plumbing retrofitted in ways that weren’t ideal, leading to moisture problems.

The Damaging Effects of Rising Damp

While the initial signs of rising damp may seem superficial, delving deeper into its effects will reveal a series of consequences. These ramifications can impact structural integrity, health, aesthetics, etc. Understanding the impact of rising damp underscores the urgency of addressing the issue and protecting the longevity of older structures.

Structural Deterioration

  • Timber decay: Continuous exposure to moisture makes timber susceptible to both wet and dry rot. Over time, affected timber loses its strength and can eventually collapse.
  • Masonry compromise: Bricks and mortar, especially in older buildings, can absorb moisture. Excessive dampness weakens the masonry, causing it to crumble or detach from adjoining structures.
  • Salt accumulation: When moisture from the ground rises, it can carry soluble salts. As the moisture evaporates, the salts crystallise, leading to ‘efflorescence’. These salt crystals exert pressure on the building’s fabric, leading to further degradation.

Unhealthy Living Conditions

Damp environments are ideal for mould growth. And when airborne, mould spores pose respiratory threats and can aggravate conditions like asthma. What’s more, the increase in moisture makes conditions favourable for dust mites – microscopic creatures that are known to trigger allergies. Finally, it’s worth bearing in mind that rising damp affects the indoor air quality, making it feel musty and leading to health issues, especially in those with pre-existing respiratory conditions. Aesthetic Damage
  • Wall discolouration: The rising moisture often carries minerals and dirt, causing unsightly stains on walls.
  • Peeling paint and wallpaper: Excess moisture interferes with the adhesion of paint and wallpaper, causing them to bubble, peel, or flake off.
  • Deteriorating plaster: Dampness can cause plaster to soften and crumble, revealing the brickwork underneath and leading to increased repair costs.

Financial Implications

Damp walls reduce a building's thermal efficiency. As a result, more energy may be needed to heat space, leading to higher energy bills. Plus, a building plagued by rising damp issues may see a dip in its market value. Prospective buyers or tenants might be hesitant, given the associated problems. And the longer the dampness persists, the more extensive the damage. Repair costs mount as a result, especially if structural repairs are required. Are you concerned about rising damp in your older property? Whether you’ve noticed some of the tell-tale signs, or simply want a survey to get ahead of any issues before they get worse, London Damp Specialists can help. Contact us today to discuss your property’s needs.

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