Devon & Cornwall are full of charming heritage houses and old buildings, each with a unique character — but also a unique set of damp problems. Unlike modern buildings, period homes were never designed with plastic barriers, cavity walls, or concrete foundations. Their solid walled structure, lime-based building materials, and naturally porous construction mean they breathe freely, absorb moist air, and release it again.
When this natural balance is disrupted, damp issues quickly follow.
In this guide, we explore why damp in old homes is so common in Devon & Cornwall, the signs to watch for, damp proofing methods, long-term benefits, and how professional support can protect the structural integrity of your property for generations to come.
If you are looking for Damp proofing sercices please contact us
Why Old Properties in Devon & Cornwall Are So Prone to Damp
Historic homes were built with permeable, breathable materials such as lime mortar, stone, soft brick, and stone or slate tiles. These materials work together to manage moisture ingress naturally. Modern interventions — such as acrylic paints, plastic coatings, cement render, and polyurethane insulation sheets — often trap moisture inside the building fabric, creating more serious damp issues over time.
Key reasons damp thrives in Devon’s & Cornwall’s older homes:
- Driving rain saturates exposed external walls, especially on coastal and moorland properties.
- Broken guttering, poor drainage or high ground levels force moisture into the masonry walls.
- Insufficient ventilation leads to condensation forms, especially in kitchens, bathrooms and rooms with double glazing.
- A blocked or missing damp proof course allows rising damp to climb interior surfaces.
- Modern renovations using modern materials interfere with the natural breathability of the structure.
Add in Devon’s & Cornwall’s climate, and problems can escalate fast.
Types of Damp Common in Heritage Homes
1. Rising Damp
Rising damp occurs when moisture from the ground is drawn upward through porous brickwork or masonry. This typically happens when a building’s damp proof course (DPC) is damaged, ineffective, or entirely absent. Many older properties were constructed before DPCs were standard, making them especially vulnerable to this type of damp.
Signs include:
- Damp patches on internal walls
- Plaster falling
- Flaky paint
- Musty smells
- Salt deposits
2. Penetrating Damp
Wind‑driven rain enters through the outer leaf of a property. This often affects cottages with old stonework or weathered mortar.
3. Condensation & Interstitial Moisture
When relative humidity rises, condensation forms on cold surfaces. Inside walls, it becomes interstitial condensation — sometimes called interstitial condensation — leading to unseen damage until rot appears.
This is exacerbated by:
- Poor ventilation
- Cold external walls
- Rooms with walls creating cold spots
Common Signs of Damp in Old Properties
Look out for:
- Damp walls and damp patches
- Peeling or flaky paint
- Rotting skirting boards
- Wet rot or dry rot
- Persistent musty smells
- Cold rooms full of moist air
A professional damp survey can confirm the extent of the issue. Reputable damp surveyors, especially those recognised by the Property Care Association, use damp meters and moisture analysis to diagnose accurately.
How Damp Proofing Works in Devon’s & Cornwall’s Older Homes
Modern solutions must be adapted carefully for heritage construction. At Peninsula Custom Construction Ltd, we use approaches that respect the historic buildings, minimise disruption, and retain original materials where possible.
Effective Damp Proofing Methods
1. Installing or Repairing a Damp Proof Course
If your property needs a new damp proof course, options include:
- Chemical damp proof or chemical DPC injections
- Injection damp proofing
- Injected damp proof formulations
These block rising moisture without damaging the structure.
Physical DPC
A barrier layer is inserted into the wall to block moisture from rising through the masonry.
Physical DPC Materials
- Slate courses – Traditional in Victorian and Edwardian buildings; thin slate layers were placed in mortar beds to block rising moisture.
- Stone layer systems – Used in some historic masonry where stone slabs acted as a natural capillary break.
- Bitumen felt – Introduced later; bitumen‑impregnated sheets provide a flexible waterproof barrier.
- Stainless steel – Durable modern option used where physical insertion is possible without corrosion risk.
- Polyethylene (PE) – Common modern plastic DPC rolls offering flexibility and long-term resistance to moisture.
- Other plastics (e.g., PVC) – Lightweight, economical options frequently used in contemporary construction.
Chemical DPC
A liquid or cream is injected into drilled holes in the mortar bed, creating a water‑repellent barrier within the masonry.
Chemical DPC Materials
- Silane/siloxane creams – Most common today, forming a hydrophobic silicone layer inside the brickwork.
- Water‑based resins – Older method where resin solutions spread through capillaries to create a waterproof zone.
Mortar Injection DPC
A special waterproofing mortar is injected into the bed joint, forming a solid damp‑resistant layer once cured.
Mortar Injection Materials
- Waterproofing mortars – Cementitious mixes enhanced with silicates or polymers to create a solid moisture‑resistant barrier.
Electro‑Osmotic DPC
Low-voltage electrical wires are installed along the wall, reversing the capillary flow of moisture so water is driven back downwards.
Electro‑Osmotic DPC Components
- Titanium or copper wire systems – Low-voltage conductors embedded along the wall to reverse moisture movement.
2. Damp Proof Membrane
A damp proof membrane can be applied internally to manage severe moisture. Care is taken to ensure this doesn’t trap moisture behind it.
Polyethylene (PE) Sheet DPM
A flexible plastic membrane—often 1200‑gauge—laid beneath concrete floors to prevent ground moisture rising into the building.
Liquid‑Applied DPM
A brush‑ or roller‑applied resin or polymer coating that cures into a seamless waterproof layer ideal for irregular surfaces.
Bituminous (Asphalt/Bitumen) DPM
A durable bitumen‑based coating or sheet used historically and in heavy‑duty applications, offering excellent moisture resistance.
Epoxy Resin DPM
A high‑performance two‑part resin system used where flooring needs a strong vapour barrier, especially after construction moisture tests fail.
Cementitious DPM
A waterproof cement‑based slurry applied to walls or floors, commonly used in basements or as part of tanking systems.
Rubber/Elastomeric DPM
Flexible, rubberised membranes or coatings that tolerate structural movement and provide long‑lasting water resistance.
3. Breathable Rendering & Plasters
Replacing gypsum plaster with lime-based or breathable materials helps walls stay dry. Waterproof plasters or waterproof paint may be used sparingly but never as a replacement for proper diagnosis.
4. External Repairs
Small tasks like fixing roof leaks, repairing mortar, or adjusting ground levels can dramatically reduce damp problems.
5. Improving Ventilation
Better airflow helps control humidity, preventing warm moist air from condensing.
6. Re‑plastering After Damp Treatment
Once walls dry, sensitive re plastering may be needed — especially when removing old internal plaster that was installed using impermeable modern materials.
Common Materials Used in Older and Modern DPC Systems
Managing Damp Long Term
Ongoing maintenance is essential for managing damp in any heritage house. This includes:
- Regular damp survey checks
- Monitoring humidity
- Avoiding plastic sheets, impermeable paints, or cement-based finishes
- Ensuring your home can still breathe freely
Costs & Benefits of Professional Damp Proofing
Investing in professional damp proofing services protects your home from:
- Timber decay
- Structural damage
- Wasted energy
- Long-term hidden repairs
It also helps ensure a healthy, dry house and preserves the original charm of your home with a proven track record of restoration success.
Why Choose Peninsula Custom Construction Ltd?
With decades of experience working on old buildings, cottages, barns and heritage properties across Devon and East Cornwall, Peninsula Custom Construction Ltd understands exactly how to handle moisture safely and respectfully. Our team selects only the right building materials, carefully avoids unsuitable modern materials, and ensures your home remains safe, dry, and structurally sound for the future.
If you suspect damp issues, contact us to arrange a damp survey or discuss tailored proofing services for your property.