What is a Magnetic DPC?
A magnetic damp proof course (or magnetic DPC) is the latest technology to solve rising damp non-invasively, based on recent technical research about the mechanism of rising damp and accompanying electrical phenomena in damp masonry.
A magnetic DPC can reverse the rise of moisture in any building fabric without any damage or physical intervention to the masonry by reducing the surface charges responsible for capillary bonding.
The concept of magnetic DPCs has been around in various forms for over 30 years. It has been developed by Electronic Engineers familiar with many aspects of building physics, applying their knowledge of Electronics onto damp buildings.
The original concept of the technology came from the medical MRI technology (Magnetic Resonance Imaging), a tissue-friendly body imaging technology which uses magnetic fields that interact with the water molecules of the body, instead of the more damaging X-ray radiation. Based on that a solution was envisioned to reduce the bonding of water vapors to capillary surfaces by means of weak magnetic fields.
Over the years various patents have been filed for both passive and active (unpowered and powered) systems. We have listed a few of them here from the Google Patents database.
Click on each title to expand its content.
This German patent from 2018 describes an electronic device that can influence capillary flow behaviour in masonry with magnetic pulses, by influencing the electrical potential of the electrical double layer.
According to the inventor, an electrical potential build-up occurs inside the capillaries on a continuous basis. The generated magnetic pulse train interferes with this, resulting in a reduction of capillary forces: "the magnetic pulse sequences influence and modify the surface tension of liquid in the capillaries in such a way that the weight of the liquid gains the upper hand and the liquid in the capillaries sinks and can flow down out of the capillaries".
This French patent from 2009 describes a passive (no power required) resonator type device, comprised of a set of electrical circuits, each of them made of a number of circular conductive concentric rings with opposite openings for the reception of telluric waves.
According to Lenz's law - an induced current in a circuit opposes the cause that generates it - these rings create a local electromagnetic field opposite (180° out-of-phase) to the disturbed terrestrial electromagnetic field, cancelling its action over the entire area of action of the device, which is about 10-30 m depending on the number and configuration of conductive rings used.
According to the author, old damp walls become dry within 6-18 months, after which the walls are protected from any capillary rise during the entire operating life of the device.
This French patent from 2008 is composed of 3 independent inductance-capacitance oscillator circuits for neutralizing electromagnetic wavelengths of telluric (Earth) origin in the VHF, UHF and microwave bands (30 MHz - 3 GHz). This invention is an improved version of a patent from 1988 from the same author, providing wider bandwidth and simpler construction.
This German patent from 2005 describes a powered device consisting of a flat Tesla coil placed in the vicinity of a damp wall (without touching it).
The application of a high-frequency weak pulsed electrical field breaks the attraction between the capillaries and water molecules, resulting in the water falling back into the ground under the effect of gravity.
This German patent from 1989 describes a non-invasive powered wall dehydration system composed of a pulse generator  and a passive LC oscillating circuit (resonator)  which is connected to an antenna, that emits low-powered electromagnetic pulses to break the capillary bond between the wall fabric and water molecules. According to the author, the range of the device is about 20 meters.
This French invention from 1988 describes two parallel oscillating circuits made of 4 spiral inductors, 4 capacitors and 4 rigid dipole antennas, mounted on insulating supports - the whole device being housed in a protective box permeable to electromagnetic fields. The unit also features an energy discharge circuit that can periodically discharge the accumulated energy of the oscillating circuits to the ground.
The device collects electromagnetic energy from the environment. its oscillating circuits create a reverse-phased field to the incoming field, which results in the cancellation of the osmotic pumping effect inside the wall capillaries. In addition, when the incoming electromagnetic fields are intense, some of the energy is discharged to an earth connection.
This US invention from 1980 presents two passive (unpowered) resonant circuits, each of them comprised of a spirally wound flat coil (inductance) connected to a capacitor located in the center of each coil. The two flat coils [1, 11] are mounted perpendicularly to each other, housed in a plastic boxlike container.
The energy of the apparatus is supplied from outside by the abnormally high electrical and magnetic fields (interference of stray fields) always present in areas of rising damp. This energy drives the two oscillatory resonant circuits, which according to Lenz's law - an induced current in a circuit opposes the cause that generates it - creates a local electromagnetic field opposite (180° out-of-phase) to to the incoming field that creates the capillary rise, reducing its effects - resulting in the dehydration of the building over the entire area of action of the device.
Although the idea that electromagnetic fields can affect the bonding of water to solid surfaces has been observed for quite some time, the underlying mechanisms has not been well understood. Because some of the underlying research has not been completed until recently, this exciting technology remained on the sidelines of science for decades.
This is not something unusual. Many important discoveries follow a 2-stage discovery process:
- Discovery by observation: a phenomenon is first observed, resulting in a limited understanding.
- Scientific explanation: following the initial discovery it can take science decades to “catch-up” and provide a full scientific explanation for the phenomena.
A well-known such example is the law of gravity, described by Sir Isaac Newton 350 years ago in 1687. Today we still don’t have its theoretical explanation, yet we know it exists.
Another example is the discovery of electrophoresis – the movement of solid particles in a liquid under the influence of an electric field – used for particle separation and modern DNA analysis. First observed on clay particles in 1807 (by Friedrich Reuss), it took science 100 years to provide a theoretical explanation for it (Smoluchowski, 1903), being implemented in scientific applications only in 1942.
The magnetic DPC followed a similar path of discovery: some of its basic phenomena has been observed in the 1980s, taking several decades for science to catch-up and clarify some of the finer details.
Working Principe – Simple, Non-Technical Explanation
The working principle of the magnetic DPC can be summarized in a nutshell as follows:
Old damp buildings contain lots of moisture in both in vapor and liquid form trapped inside billions of capillaries. Water bonds to wall surfaces due to surface charges - small electrostatic charges between water molecules and capillary surfaces.
Surface charges are not fixed, but variable. They are influenced by a number of phenomena, including the intensity of magnetic fields in the building. Higher magnetic fields result in higher surface charges and more capillary bonding. Lower magnetic fields result in lower surface charges and less capillary bonding.
The magnetic DPC is an electronic system designed to absorb certain magnetic fields responsible for capillary bonding, discarding it to the ground via an earthing connection.
Less energy results in decreased surface charges and less capillary bonding, allowing water molecules to debond from capillary surfaces, evaporate out freely into the environment.
Once the magnetic DPC is installed in the building the moisture content of the walls gradually disappears, resulting in a significantly drier wall fabric.
By decreasing the surface charges, the magnetic DPC enhances the wall's natural breathabilty.
Working Principle – A More Detailed Explanation
The dominating force in the lower part of the walls (under 1 m) that determines their condition is soil evaporation. Water vapors from the ground from under the walls evaporate upwards into the porous wall fabric, leading over time to a natural moisture accumulation known as rising damp. The main wetting mechanism near the ground is vapor movement, not liquid capillary action as previously thought, as walls are built on damp soil not liquid water.
Unfortunately, not all moisture that moves into a wall fabric evaporates out. Recent research has shown, that even if the fabric is fully breathable (e.g. bare bricks with lime), a significant amount of moisture is permanently retained by the wall fabric and never evaporates. This is cue to the presence of surface charges inside the walls.
Surface charges are tiny electrical charges (voltages) on the capillary surfaces. These charges attract electrostatically the flying vapor molecules, leading to moisture accumulation in the masonry, ultimately resulting in liquid moisture and capillary action. The liquification of vapors in the capillaries does not occur due to condensation (temperature differences) but because of vapour saturation (pressure) from the ongoing 24/7 soil evaporation.
Surface charges are not fixed but variable. They are influenced by a number of environmental factors, including electro-magnetic fields present in the environment.
The Effect of Magnetic Fields onto Water
Hydrogen ions (protons) from water have a very interesting property: they spin around their own axis generating their own magnetic field. As a result they act as tiny magnets which can be individually influenced and re-oriented by any external magnetic field.
- Higher magnetic fields in the environment align the tiny "hydrogen magnets", resulting in stronger surface charges and a better bonding of water to capillary surfaces.
- Lower magnetic fields relax and randomize the orientation of "hydrogen magnets", resulting in lower surface charges and weaker bonding of water to capillary surfaces.
Once the DPC system is installed in a building, its internal circuitry absorbs some of these fields, channeling their energy into the ground through an earthing connection. resulting in reduced surface charges and less capillary bonding. The moisture stored in the walls freely evaporates out and the wall fabric gradually dries out.
Internal Construction - The Circuitry
How does the magnetic DPC absorb magnetic fields from the environment and thus decrease the walls' surface charges? Here are some technical details about its circuitry.
Each DPC system is comprised of the following three main modules:
1. Energy Intake Module: responsible for the collection of electro/magnetic energy from the environment using a special set of aerials (spiral antennas), covering a very wide frequency band. The collected energy is then transferred through a hard wired connection to the electronic filtering module located under it.
2. Electronic Filtering Module: is a complex network of precisely tuned electronic filters (band-pass filters) realized on one or more circuit boards, responsible for the electronic filtering of specific frequencies that contribute to capillary action. These frequencies are absorbed by the circuitry and their energy is transferred to the ground via an earthing connection. Wi-Fi, mobile signals etc. are not affected at all.
3. The case: the case is permeable to magnetic fields, having both a functional and protective role. The case has an earthing wire attached to it connected to the ground.
The unit is not powered only earthed. The power is in the environment in form of magnetic fields that increase the surface charges and keep the wall fabric in a charged-up state. We need to "unpower" the walls from the surrounding environment to reduce the surface charges and capillary bonding.
Here are some more technical details for engineers or anyone interested.
1. Energy Intake Module
The main role of the energy intake circuit is to collect energy from the environment. This is done by using passive (non-powered) spiral antennas.
Antennas (or aerials) are fundamentally energy converters which convert electromagnetic waves into electrical voltages and currents. In its simplest form, an antenna is a piece of conductive wire (copper or aluminium) in which changing ambient fields (E) induce a voltage (V) or current (I) through electromagnetic induction.
The antennas used in our magnetic DPC system are three-arm spiral antennas. Spiral antennas are special type of antennas invented in the mid-1950s, by wrapping the arms of a simple antenna around each other to form a spiral. This resulted in a very wide bandwidth antenna with a flat, compact construction, widely used today in the defence and communication industry in military aircrafts, GPS receivers, satellite communications networks etc.
The spiral antenna construction allows the system to collect as much energy as possible from the environment on a wide frequency band, transferring that energy through a hard-wired connection in the center to the lower filtering module.
2. Electronic Filtering Module
Research has shown that certain frequencies of the surrounding electric and magnetic fields are especially capable of affecting the movement of water and its bonding to wall capillaries. Water molecules being polar in nature (with one positive and one negative side), are susceptible to external fields. By eliminating certain frequencies, one can cancel the osmotic pumping effect responsible for rising damp – which is the role of the filtering module.
The electronic filtering module is a network of precisely tuned LC band-pass filters, realized with two oppositely wound spiral antennas placed on the opposite side of a printed circuit board (PCB). Their fields intersect, forming a complex inductive-capacitive (LC) network. Due to its technical complexity, we are not going to go into further details of the filtering mechanism – the important point is that certain frequencies are filtered out and their energy absorbed from the frequency spectrum - thus eliminating the key frequencies that actively contribute to the formation of rising damp.
Here is a demonstration of the practical filtering capability of the filtering network, shown on the screen of a spectrum analyzer in the research lab:
The filtered out frequencies show up above as high vertical peaks on the instrument's screen, in comparison to the rest of the frequency spectrum (horizontal base line at the bottom).
3. The Case
The case is permeable to magnetic fields and it plays an active role in the functioning of the device. It is a passive cavity resonator (or microwave cavity resonator) that further assists with the filtering and suppression of certain frequencies, making the unit perform better.
The case works similar to the sound box of a musical instrument or an organ pipe, reinforcing certain standing waves in the cavity, acting as a band-pass filter, allowing certain frequencies to pass while blocking others.
Here are some photos of our residential magnetic DPC systems showing their internal construction. Larger commercial units are much more complex with additional circuits / components, but their overall working principle is the same.
Finally, here are a few UK installations showing various systems fitted in different buildings.
Here is some of the research data supporting the above findings.
Magnetic Fields and Surface Charges
Earth's magnetic field has ongoing variations that often arrive as a series of fast-changing high-amplitude magnetic pulses, known as magnetic pulsations, which can be captured anywhere on Earth with sensitive enough magnetometers.
These magnetic pulsations (orange) penetrate the walls and generate fast-changing voltage and current variations with very sharp fronts, injecting energy into the wall fabric, leading to increased surface charges resulting in stronger capillary attraction.
The reason why these transient effects have not been detected in damp walls earlier it can be attributed to a combination of several factors:
- Multidisciplinary knowledge: in order to look for and detect this data - in addition to architectural and building knowledge - one also must have a thorough understanding of Electronics and geomagnetic phenomena, seemingly unrelated disciplines to building sciences.
- Sensitive instrumentation: while basic detection of some of these signals can be done with hobby multi-meters, for accurate mapping and in-depth understanding expensive professional measurement instrumentation is necessary.
- They become visible only at fast data sampling: most building-monitoring focuses on long-term trends, taking readings at large intervals (every 5-60 minutes). The variations described above are very fast, short, transient phenomena which can only be detected with very fast measurements. At slow sampling rates these transient pulses become invisible thus undetected.
The dehydration effect of the magnetic DPC has been subject to extensive long-term testing through embedded micro-sensors taking consecutive readings from the soil, the depth and surface of masonry as well as the surrounding environment – monitoring the movement of moisture throughout the wall fabric.
Before the installation of the magnetic DPC system in the building, the moisture content of the walls was slowly but consistently decreasing.
After the installation of the magnetic DPC things changed. The first changes have been observed a few days later when wall voltages started increasing first in the mortar (grey line), then in the bricks (red line). As explained earlier, decreasing voltages denote wetting (more liquid moisture in the walls - before the magnetic DPC), while increasing voltages denote drying (less liquid moisture and more vapors - after the magnetic DPC).
Following the installation of the magnetic DPC, wall voltages (red) keep increasing, while humidity inside the wall (green) keeps dropping. The automatic trend lines show this clearly.
- Moisture from the ground evaporates into the wall fabric, gradually wetting the capillaries through combined vapor and liquid transport.
- Surface charges are small electrical charges on the surface of capillaries. Moisture bonds to capillary surfaces due to the presence of surface charges.
- Hydrogen ions in water are spinning around their axes, generating their own magnetic field, their orientation determining the bonding strength of water molecules to capillary surfaces. This can be influenced by external magnetic fields.
- Stronger magnetic fields align the hydrogen magnetic vectors resulting in increased surface charges, making water bond to capillary surfaces stronger. Weaker magnetic fields in the building do the opposite, they randomize and relax the hydrogen magnetic vectors, resulting in lower surface charges that make water molecules bond less to capillary surfaces.
- The magnetic DPC reduces the capillary surface charges by absorbing certain magnetic fields (frequencies) that contribute to the charging of capillary surfaces, by channeling their energy to the ground through an earthing connection. The reduced surface charges make the wall fabric more breathable, allowing more moisture to evaporate – even moisture accumulated long-term.
- Magnetic DPCs offer a non-invasive permanent solution to the problem of rising damp, which is one of the leading causes behind the decay of old buildings, worldwide.1Franzoni, Elisa. (2014). Rising damp removal from historical masonries: A still open challenge. Construction and Building Materials. 54. 123-136.
|1||Franzoni, Elisa. (2014). Rising damp removal from historical masonries: A still open challenge. Construction and Building Materials. 54. 123-136.|