What are damp treatment products and do they work?
Contact us if you need help with damp - 01626 872886 .
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We are long term members of the PCA - The Property Care Association - the professional body for the Damp Proofing industry and our Dampness Surveyors have over 50 years of experience between them.
Want Help choosing a Contractor - E: Mail us at help@propertyrepairsystems.co.uk
Damp Proofing Products
What is a chemical damp proof course
Chemical damp-proof courses are inserted to control the vertical passage of moisture from the ground upwards through building materials (brick, stone, concrete) and are almost all installed in properties where no damp-proof course exists, or it has broken down with age (not a common occurrence, contrary to popular opinion in the Damp Proofing Trade).
We specialize in finding out the real cause of your dampness and then giving you the facts. Only when you have those facts should you make any decisions about products. In many situations no specialist products are required - only general maintenance items available from B&Q and Homebase. If you do need anything special we may offer to supply it - but you have no obligation to purchase from us.
Most chemical damp proof courses are not required and have no useful effect. There are simple reasons for this, which are happy to discuss by letter, E Mail or telephone.
How is a modern chemical damp proof course installedChemical damp-proof courses should be installed in a position in accordance with good practice as described in BS 6576:1985, "Code of Practice for the Installation of Chemical Damp-proof Courses", a minimum of 150mm (6 inches) above external ground level, in external walls. If the installer does not follow the basic rules the damp proof course will be useless.
Additional rules apply to cavity walls, vertical damp proof courses and internal walls.
So called DPCs are installed in walls by various methods depending on the particular system being employed, but the ultimate objective is to provide a water repellent or pore blocking material in a continuous horizontal band in the masonry, to act as an effective 'barrier' to water rising from the ground.
These days Silicone Cream emulsion is used most commonly. It requires no special equipment to install, no pressure and has no chemical hazards.
Check the source of your damp for yourself - it is not difficult - click here
See our Article about installing different types of Damp Proof Course - click here.
See our Shop for damp proofing pumps and equipment - click here
For help with installation methods and rules call our experts on 01626 872886 .
Want Help - E: Mail us at help@propertyrepairsystems.co.uk
What types of damp barrier can be used as a damp proof course?Historically, a variety of materials have been installed during the building process - stone, slate, lead, zinc and stainless steel and more recently (and currently) plastic.
However, once a building has been erected it is more difficult to insert a physical DPC (although stainless steel sheet can be vibrated into walls, via saw cut slots), so other methods have been developed for remedial action;
1. Water repellent - liquid, paste, gel, or cream by injection - amateur and professional
2. Pore blocking - cement based mortar, by injection - mainly professional
3. Osmotic - passive or active, via embedded wires - mainly professional
For help with types of damp proof course call our experts on 01626 872886 .
How are different types of damp proof course installed?
1. Water repellent type- holes, usually between 10-12mm in diameter, are drilled either into the mortar joints or via the bricks or stones and the chemical is injected using a high pressure pump (liquids) or low pressure hand pump or skeleton gun (creams, pastes and gels). The chemicals spread through the damp masonry, over a period of several months, to join up and form a continuous water repellent layer. This is NOT a solid vapour barrier - it prevents further liquid water from passing through, thus allowing the wall to dry out.
2. Pore blocking type - the cement based injection mortar is mixed with water to form a 'slurry' and injected from a re-usable, plastic bodied, heavy duty 'gun'. It rapidly sets, giving off great heat, to form a solid plug in the wall. The holes are generally 18-20mm in diameter and this method is only really suitable for thick, stable stone walls. The injected mortar then slowly generates impermeable 'salts', which over several months block the pores in the wall and prevent moisture from rising. This method requires large drilling machines, expensive drill bits and mortar guns, making it uneconomic for amateur use.
3. Osmotic types - the old, 'passive' system used copper wires, which unfortunately corroded, but the latest Lectros Active System utilises a titanium wire, connected to a special mains powered control box, which is run around the walls rather like a ring main. Bent at regular intervals to form anodes, the wire loops are inserted into large holes drilled into the wall (internally, externally or both if necessary). The wire is hidden in formed "chases" or existing, raked out brickwork joints and the whole system is earthed. The electricity from the mains supply passes through a transformer, through the anodes and to earth, setting up an electrical field, which repels the damp. The holes are filled with a special mortar, to ensure good conductivity. This method requires large drilling machines, expensive drill bits and special mortars, making it uneconomic for amateur use.
For help with methods of damp proofing call our experts on 01626 872886 .
Why are Injection Creams better than liquids, gels and solid sticks
The technical review below summarises the problems of the last generation of liquid damp proofing systems. Our New Generation Creams are infinitely better for the following reasons:
- no pressure is used in placing the cream in the hole, so no losses down cracks and crevices
- gradual spread of the cream giving even distribution, unlike liquid short term squirt and stop techniques
- no solvents to evaporate, so no smell, no health hazards and nice slow spread
- not caustic and non-staining, unlike the old water based DPC Fluids (Siliconates)
- no solid stick to push into a ragged hole and a lot cheaper
For help with Silicone Creams call our experts on 01626 872886 .
Do pressure injected liquids work as a damp proof courseUnlike a physical damp-proof course these injected liquid damp-proof courses do not form a 'discrete impermeable plane', but more of a 'diffuse band'. When fluids are injected into a heterogeneous substrate such as brick/mortar they do not totally fill up the porous structures and neither do they completely push out the water in front of the advancing injection fluid as is so often claimed. Instead, the fluid tends to 'finger' within the substrate, a process known as 'viscous fingering'. The fingers of the injected material form when the fluid takes the lines of least resistance such as the larger pores and cracks. Unfortunately, such pathways are not the most important elements in the conductance of water up the wall. Furthermore, the damper the substrate the greater this fingering is likely to be, especially with solvent based systems since these are not miscible with the resident moisture. Fingering is also increased by injection at high pressure. Reduction of the phenomenon is obtained by low pressure injection or, better still, by gravity diffusion of the DPC fluid.
For help with pressure injected damp proof courses call our experts on 01626 872886 .
Why can liquid pressure injection be incompleteThe result of the damp-proofing fluids forming fingers give rise to non-impregnated 'pools' within the wall through which water can continue to rise. In the case of pressure injection damp-proof courses, this suggests that it is unlikely that the diffuse band of the damp-proofing agent will be totally complete. The resultant chemical damp-proof course may therefore not stop rising dampness by causing an immediate cut-off of rising water above the damp-proof course like that effected by a physical damp-proof course. Instead, a relatively rapid decline in the moisture gradient should occur above the inserted chemical damp-proof course due to the 'control' exerted. Thus, in practice, the rising ground water should be reduced to such a level that, in association with specialist replastering, it should no longer cause decorative spoiling or damage.
For help with pressure injected damp proof courses call our experts on 01626 872886 .
What other factors reduce the effectiveness of liquid systemsThe efficacy of the water repellent damp-proofing systems can be affected where there are detergents (surfactants) impregnated into the wall by, for example, past leakage from sink waste pipes. A similar problem may occur when walls are sterilised against dry rot infection by biocide formulations containing surfactants. The overall effectiveness of a remedial damp-proof course can be investigated by examining the relationship between the distribution of free moisture (water due to rising dampness or other source of active water ingress) and contaminant salts (chloride and nitrate). Where rising dampness is still active capillary moisture will be found to the full height of salts. The absence of capillary moisture in the presence of salts arising from rising dampness indicates that drying back has occurred and that the damp-proof course is effective. Intermediary stages are also found which demonstrate different degrees of control of the rising dampness. If chloride and nitrate are not detected in a sampled profile it is possible that the ingress of moisture is due to recently developed rising dampness or more likely through rainwater penetration, condensation, plumbing defect or other sources.
For help with pressure 'salts' analysis call our experts on 01626 872886 .
How do you test a chemical damp proof courseWhen evaluating the efficacy of remedial damp-proof courses care must be taken not to misinterpret electrical moisture meter readings; high readings might not indicate that the damp-proof course itself has failed. They may reflect a number of possibilities including contaminated or inadequate plasterwork. Thus, an accurate assessment of the efficacy of a damp-proof course can only be undertaken by determining full moisture profiles linked with analysis for contaminant salts. It is also important to give consideration to the expected performance and limitations of the installed system as described above.
NOTE: It is identified in BS 6576:1985 that where timber suspended floors are encountered the damp-proof course must be injected, where possible, below joist level; this is to protect the embedded timbers from dampness and the risk of fungal decay. However, given the likely efficacy of injection systems the embedded joist ends could still remain in contact with damp masonry even if above the injected damp-proof course and may therefore remain at risk to fungal decay. It would be considered prudent that in all cases where a damp-proof course is installed in relation to a timber suspended floor, action is taken to protect any embedded timbers just above and certainly below the injected damp-proof course to prevent potential decay! Boron Gel, injected Boron Paste and the insertion of a plastic membrane can all be used to protect vulnerable joist ends and bearings. Do NOT bag joist ends in plastic - this can lead to serious decay, due to condensation and lack of breathing.
For help with testing a damp proof courses call our experts on 01626 872886 .
Learn from the UK's greatest Expert: become your own expert - save money.
Quick DIY Master Class in Dampness and Condensation - become your own Expert in 1 hour! Buy our "Dampness in Buildings" reprinted book by the great expert Graham Coleman. A great read, short and to the point.
Quick DIY Master Class in Dampness and Condensation - Click here to buy the reprint.
This book was written by Graham Coleman, who is a Lecturer in dampness and who has set many of the examinations.
He confirms in his book that a Damp Meter is not be be used to confirm that rising damp is present and he also explains how proper tests can be performed.
In practice these tests are rarely needed - simpler, less expensive options exist - but in 'legal' Cases Graham is often involved as an Expert Witness.
Click here to see our Dampness Guide for using a Damp Meter - page 1
Click here to see our Dampness Guide for using a Damp Meter - page 2
How do Air Gap Membranes work above ground
By providing a total barrier between the old damp salt contaminated wall and the new plaster and decorations.
The dimples against the wall cause an insulating air gap to be created.
The Membranes are fixed in place using plastic plugs fitted with neck seals, no moisture or moisture vapour can pass through into the decorations.
How do Cavity Drain Membranes work below ground
By providing a total barrier between the old damp salt contaminated wall and the new plaster and decorations.
The dimples against the wall cause an insulating air gap to be created which also acts as a drainage space for water, which can flow down, under the floor membrane, into a drain or sump with a pump fitted.
The Membranes are fixed in place using plastic plugs fitted with neck seals, no moisture or moisture vapour can pass through into the decorations.
What is Tanking?
Tanking is a loosely used term that should mean the formation of a sealed Tank by the application of waterproof liquid membranes to walls and floors.
Brushing on cement based Tanking Slurry
Why not use Tanking above ground?
Because sealing floors and walls causes the trapped damp to be forced sideways and upwards, thus causing trouble in new areas for as long as water is available.
Can a Damp Meter be used to confirm rising damp - no it cannot, so do not be fooled by Surveyors
Natural Rising damp is very, very difficult to confirm. It requires the use of Laboratory Testing and wall samples taken from multiple locations for each wall.
So when a local 'expert' or 'specialist' using a so-called Damp Meter advises you that you have Rising Damp and offers to inject and replaster the walls, ask them if they have any qualifications and if they have read this book.
Damp Meters cannot measure damp at all - they measure electrical capacitance or resistance - so are only useful for comparative readings. They cannot diagnose rising damp on their own.
Quick DIY Master Class in Dampness and Condensation - Click here to buy the reprint.
This book was written by Graham Coleman, who is a Lecturer in dampness and who has set many of the examinations.
He confirms in his book that a Damp Meter is not be be used to confirm that rising damp is present and he also explains how proper tests can be performed.
In practice these tests are rarely needed - simpler, less expensive options exist - but in 'legal' Cases Graham is often involved as an Expert Witness.
Click here to see our Dampness Guide for using a Damp Meter. - page 1
Click here to see our Dampness Guide for using a Damp Meter. - page 2
Property Care Association
We are long term members of the PCA - The Property Care Association - the professional body for the Damp Proofing industry and our Dampness Surveyors have over 50 years of experience between them.
If you prefer to use a Contractor, rather than our free advice service, then go to the PCA Website where you can find the nearest qualified specialist companies. They should give you the same information that we provide. If in doubt E Mail their Reports to us for checking, before spending any money.
Link for the PCA - click here.
Want Help choosing a Contractor - E: Mail us at help@propertyrepairsystems.co.uk
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Site written by: David Moore
David Moore, B.A. (Hons.), C.T.I.S., C.R.D.S. Technical Author
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