The Importance of a Damp Proof Course
Damp proof courses are the PRIMARY LINE OF DEFENSE against rising damp. Their role is to stop the rise of water into the building fabric by "sealing off" the building from the soil and water table, thus protecting the building.
For solving rising damp long-term, fitting a damp proof course MUST be part of the rising damp remedial works. This does not have to be an invasive action - for older or listed buildings fitting a magnetic DPC is a hassle-free, non-invasive excellent option.
OTHER renovation actions - such as fitting drainage, having heating and ventilation, replastering with lime etc. - are NOT a substitute for a damp proof course, and as a result, despite the improvements they make, they won't solve your rising damp problem. The technical reasons are discussed in detail here.
Several damp proof course technologies exist. These all differ in implementation, efficiency and longevity - here is a short development timeline and summary for each.
Types of Damp Proof Course Technologies
The technology of damp proof courses (DPCs) has constantly evolved. The Victorians used solid DPCs made of slate, vitrified bricks or lead sheets. After WW2 chemical DPCs became the new thing. In the 1970-80s electro-osmotic DPCs have been invented, then from the 1980s onward various electromagnetic or wireless DPC solutions have also been added to the list of available DPC solutions.
Each DPC technology was a natural evolution over its predecessors, attempting to improve and simplify the process, while also addressing the shortcomings of previous generations. Here is a quick overview of the main DPC technologies.
Original Solid DPCs
Based on written records, original solid DPCs date back to around the 1840s, possibly earlier. They were the first attempt to solve the problem of capillary rise, during times when buildings were generally erected onto the soil. After a few decades or centuries this resulted in rising damp, causing fabric decay, high humidity, health issues etc.
The most common materials used for damp proof courses in the Victorian age were slate bedded in cement, hot asphalt, sheets of lead, glazed bricks and vitrified stone-ware tiles.
As we already know today, these "original" damp proof courses lasted from a few decades to about a century, eventually failing as they aged, as the lifetime of a damp proof course is shorter than of the building. Technical solutions had to be found to retrofit old buildings with new DPCs in order to keep rising damp in check.
Retrofit Solid DPCs
The first attempt to repair aged, decayed DPCs that reached their end of life, was to add impervious bricks to the base of the walls, or cut the walls with a large chainsaw and drive stainless steel plates into the cut. As you can imagine, this was a very invasive and very labor intensive task.
Technical advancements in chemistry made the retrofitting process simpler and less invasive by injecting waterproof chemicals into the walls. This reduced the workmanship to a few drilled holes every few inches. Nevertheless, the injection process was still fairly invasive, leaving permanent marks on buildings, while giving variable results.
Further technical research into molecular phenomena and a better understanding of electrokinetic phenomena made possible a newer, smarter, less invasive approach, by applying a small voltage to the walls through embedded wires.
But it was not all perfect, the main reasons why electro-osmotic DPCs failed over time were the corrosion or physical damage to the wires (as shown below), and more importantly, later findings have shown that in high salinity environments (e.g. old, porous, salt-laden walls) natural electro-chemical effects in the masonry rendered the system ineffective.
Magnetic DPCs attempted to address the shortcomings of electroosmotic DPCs. New discoveries about Earth's energetic background, as well as advancements in radar and telecommunications technology, paired with some clever practical electronic engineering resulted in the elimination of the trouble-prone wires - providing a truly contactless, non-invasive and hassle-free solution to rising damp. One magnetic DPC unit that looks like a small lampshade can cover the whole building, completely eliminating rising damp without invasive building work or damage to the fabric,
Which One is Best for You?
Although there are significant differences between the practical implementation, life expectancy, cost and the long-term efficiency of these solutions, fundamentally all of them attempt the same thing: to prevent the rise of ground water into the walls.
Which one is the best option for you, it depends on the building and your own situation. Although no solution fits all, here are some pointers which might help you with your decision:
- Historic and listed buildings: for historic and listed building owners, when the wall fabric can't be damaged, magnetic DPCs are the best (and only) DPC option.
- Solid walls: solid stone or rubble-filled walls (found in many cottages, farm buildings or Victorian solid walls) with a fabric made of a wide variety of building materials, an irregular course and all sorts of voids and cracks in the fabric, can be a challenge to be damp proofed. These walls can be dried out without any issues with a magnetic DPC.
- Longevity: the real life performance and longevity of various DPC solutions can differ significantly, regardless of the offered paper warranty, Do you homework to choose the best one for you.
- Insurance backed guarantee: if an insurance backed guarantee is very important, then chemical DPCs are probably the best choice. Being the mainstream solution, they are most recognized by insurance companies.
Our 32-page PDF publication - DAMPNESS IN OLD BUILDINGS - will help you with the decision. It is very thorough, written in plain English, with lots of pictures and among others, covers the following topics:
- An overview of the main moisture sources in a building
- A historic overview of rising damp
- How you can diagnose rising damp, its visual signs with many pictures
- Damp proof course (DPC) solutions on the marketplace, their pros and cons
- Magnetic DPCs, the latest technical innovation
- The basics if renovating old buildings
- The top 5 renovation mistakes you must know about
- How to deal with condensation and mould... and more
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