What is Damp Proofing?
Damp proofing is a generic term for controlling moisture within walls of a building. Damp proofing can come in many forms of treatments and within the UK there is a British Standard document that lists and describes the approved methods of damp proofing walls. This document is called the BS: 6576 2005 Code of practice for diagnosis of rising damp in walls of buildings and installation of chemical damp-proof courses.
Do I need a damp proof injection?
The chance of needing a damp proof injection is slim as most properties in the UK from 1875 onwards will usually have a physical damp proof course present. It became mandatory from 1875 with the introduction of the Public Health Act for properties built from this year onwards to have a physical damp proof course inserted during the building. So remember if your property is post 1875 a physical damp proof course is likely to be present and that the chances of needing a chemical injection is very slim.
When evaluating dampness in a wall, the damp proof course level should be assessed for bridging points i.e. high ground levels, plasterwork in contact with solid floors, external renders concealing the damp proof course and if there is any debris within a cavity, if you are dealing with a cavity wall. If any of the above bridging points are present then a damp proof injection is usually not necessary.
When dealing with properties pre-1875 then you are more than likely dealing with a historic building and a completely different approach must be adopted. Give us a call and quote our heritage damp and timber survey for further information.
What is a damp proof course?
A damp proof course or more commonly known as a DPC is an impermeable barrier within a structure preventing the movement of capillary moisture through it. A damp proof course is normally found horizontally and should be placed 150mm above the external ground levels.
What is a damp proof membrane?
A damp proof membrane, known also as a DPM is an impermeable barrier usually polyethylene, that is laid during an installation of a solid floor. This will form a barrier to prevent the movement of moisture through it. The incorporation of a damp proof membrane became mandatory in 1960 during the installation of solid floors.
Do I need to remove plasterwork during damp proofing?
Plasterwork is usually removed up to 1 meter from floor level where rising damp is present. By removing plasterwork this is removing hygroscopic salt contamination which has been transferred into the wall plaster via capillary movement and evaporation (Rising Damp). If plasterwork is not removed then the hygroscopic salts will remain in situ and the wall plaster will always remain damp.
What are Hygroscopic Salts?
To define the term Hygroscopic, this is the ability of a substance to attract and hold water molecules from the surrounding environment. This is achieved through absorption of a substance becoming physically changed, in the case of Rising Damp, becoming soluble/deliquescent.
Therefore hygroscopic salts i.e. nitrates and chlorides which are associated with Rising Damp and are found within plasterwork if not removed will absorb atmospheric moisture presenting damp walls.
What types of chemical injections are approved and listed in the BS 6576 2005?
There are five approved methods in the UK for chemical damp proofing which are:
- Pressurised Solvent-Based Fluids
- Pressurised Siliconate Fluids
- Pressurised Micro-emulsions
- Hand insertion - Injection Mortars
- Hand insertion - ready-to-use thixotropic materials
All five damp proofing methods require specific conditions for them to work correctly therefore is crucial to have a damp proofing survey carried out by a CSRT surveyor prior to spending money on damp proofing. The most commonly used in properties throughout the UK is the Siliconate Fluids and thixotropic materials.
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