Damp is it a Myth?

Understanding the Real Causes of Damp in Your Home

You may have heard the claim that rising damp is a myth but in reality, it’s far more complex. Our damp proof specialists in identifying and treating the true cause of damp, not just the symptoms. In this article, we break down the common misconceptions and the genuine reasons your walls may be wet, flaking, or growing mould.

The Myth of Rising Damp

Some experts argue that rising damp doesn’t exist. The truth? Water does rise in masonry—but what matters more is how it’s getting into the structure in the first place. That’s where professional diagnosis becomes essential.

At Trace, we inspect for rising damp, but more importantly, we focus on ruling out everything else first. Often, symptoms that look like rising damp are caused by other common issues.

Common Defects That Cause Damp Symptoms

1. Leaking Drains

Persistent leaks around or beneath a property often go unnoticed, but they create ideal conditions for moisture to accumulate at the base of the structure. This consistent water exposure increases the risk of damp travelling into masonry, even if a damp proof course is present. Over time, porous or degraded materials will absorb the moisture, allowing it to rise and affect internal walls, floors, and finishes.

2. Bridging Plaster Over the DPC

If plaster extends too far down and bridges the damp proof course, it can draw moisture from the floor or wall base and carry it upwards. This capillary action often mimics the appearance of rising damp, even though the moisture hasn’t travelled through the masonry itself. It’s a common issue in older properties and refurbishments where correct detailing around the DPC is overlooked.

3. External Render Bridging the DPC

External render that overlaps the damp proof course or meets raised ground levels can allow water to enter the structure from the outside. Rain splashback and groundwater absorption can bypass the DPC, leading to dampness rising inside the property. Without proper detailing or cutbacks in render height, moisture may track into the internal walls and compromise finishes.

What About ‘True’ Rising Damp?

In some cases, rising damp genuinely occurs—especially when no DPC is present or if it has failed. However, confirming this is difficult without extensive lab testing. We use practical, evidence-based approaches such as Speedy Moisture Meters and visual inspections to make informed, sensible recommendations.

Hygroscopic Salts and Tanking Gone Wrong

Modern tanking systems often block moisture from escaping, pushing it higher up the wall and drawing salts with it. This can lead to visible damp lines above treated areas, especially if:

• Vapour barriers are used inappropriately.
• Gypsum-based plaster is used instead of breathable lime plaster.
• Drying time isn’t respected before decorating.

Real-World Issues We See Every Week:

1. Incomplete Plaster Removal

Leaving behind a narrow band of salt-contaminated plaster often results in damp reappearing just above the treated area. Proper identification of salt migration is essential.

2. Poor Quality DPC Injection

We often find DPC holes drilled too shallow or spaced incorrectly, meaning the damp proof course never functions properly. Some installations also use insufficient chemical volume or unsuitable materials.

3. Skirting Boards and Joinery Trapped by Wet Floors

Contractors sometimes install joinery or fit plaster before floor screeds are laid, causing water vapour from the floor to be trapped behind timbers. This leads to dampness, decay, and even fungal growth.

4. Floor Screeds Laid After Joinery

If the screed is laid after timber elements are installed, any moisture in the subfloor gets sealed beneath the new surface, where it moves laterally and eventually affects walls and woodwork.

5. Failure to Link the DPC to a Floor Membrane

Without a proper wall-to-floor joint, moisture escapes at the junction and damages low-level plaster and skirting. It’s a common cause of so-called 'rising damp' symptoms.

These issues often occur during renovations and can create more damp problems than were originally present—proving that poor workmanship or rushed schedules can be just as much to blame as failed damp proof courses.

So what’s the solution?

The key is correct diagnosis. At Trace, we look beyond the obvious signs. We investigate floor/wall joints, test plaster for salts, inspect drain systems, and only recommend DPC injection when it’s genuinely needed.

Sometimes the answer is as simple as removing bridging plaster or using the right breathable lime plaster finish. Other times, a full DPC installation is necessary. Either way, our advice is based on evidence, not guesswork.

Final thought

Rising damp isn’t always what it seems—but that doesn’t mean your walls aren’t damp. The real question is: why?

Let Trace Basement Systems help you find out.

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