Chemical injected DPC
Rising damp is caused by capillary action drawing moisture up through porous elements of a building’s fabric. This can result in:
- Condensation or damp patches (typically up to 1 m above the floor).
- Corrosion of metal elements such as beading.
- Damp odours.
- Timber decay, such as skirting boards.
- Damage to surface finishes.
- Tide marks and staining (typically up to 1 m above the floor).
- The presence of white salts.
- Health problems.
Modern buildings avoid rising damp by the inclusion of a damp-proof course (DPC), a barrier, usually formed by a membrane built into the walls. However, older buildings may not have a DPC. In this case, a chemical injected DPC can be inserted to create a continuous chemical barrier to rising damp.
A series of holes are drilled into the wall at low level, the number and pattern of which is determined by the construction of the wall and its thickness. High and low pressure injection can then used to introduce a water-repellent chemical fluid that penetrates across the wall and between the holes forming a continuous barrier.
Treatment generally also involves remedial work to any corroded or decayed elements of the building fabric, as well as hacking off and replacing existing plaster to a height of 1 m (sometimes replacing it with a waterproof plaster). However, this can be very disruptive as sockets have to be taken out, skirting boards removed, radiators removed and so on.
The technique is best suited to brick or block buildings, as they tend to be of a relatively uniform construction. However, it may not be effective if any gaps are left in the wall construction, or if gaps form over time with material deterioration. Equally, if the method is applied to walls that comprise materials of varying permeability levels, such as walls with rubble infill, it can be unreliable as the injected solution may not accumulate where it is required in the sufficient quantities. This can be due to the solution following the lines of least resistance in the wall material.
Damp in some older buildings may actually be caused by a leak or a defect in the wall construction, such as a cracking, rather than by rising damp, and this may not be rectified by the insertion of a damp-proof course. It is important therefore that any defects are identified and corrected first before accepting the cost and disruption of inserting a damp-proof course.
Other solutions might include the insertion of a DPC (rather than injection) or drainage solutions such as french drains.
[edit] Related articles on Designing Buildings
Featured articles and news
Key takeaways from the BSRIA Briefing 2024
Not just waiting for Net Zero, but driving it.
The ISO answer to what is a digital twin
Talking about digital twins in a more consistent manner.
Top tips and risks to look out for.
New Code of Practice for fire and escape door hardware
Published by GAI and DHF.
Retrofit of Buildings, a CIOB Technical Publication
Pertinent technical issues, retrofit measures and the roles involved.
New alliance will tackle skills shortage in greater Manchester
The pioneering Electrotechnical Training and Careers Alliance.
Drone data at the edge: three steps to better AI insights
Offering greater accuracy and quicker access to insights.
From fit-out to higher-risk buildings.
Heritage conservation in Calgary
The triple bottom line.
College of West Anglia apprentice wins SkillELECTRIC gold.
Scottish government launch delivery plan
To strengthen planning and tackle the housing emergency.
How people react in ways which tend to restore their comfort.
Comfort is a crucial missing piece of the puzzle.
ECA launches Recharging Electrical Skills Charter in Wales
Best solutions for the industry and electrical skills in Wales.
New homebuilding skills hub launch and industry response
Working with CITB and NHBC to launch fast track training.