If all else fails then "Tank"

DISCLAIMER:

These notes and web pages are for information and general guidance only and are not to be considered as a complete technical description of the subjects covered. Furthermore, due to the nature of old constructions and the large number of variables that need to be considered it would not be possible to form a judgement based solely on these pages. The author and anyone else representing Reddock Consultancies cannot accept liability for the consequences of anyone acting on the information here given.

© 2010/2016    S.E.Reddock, M.Sc., C.Eng.

Reddock Consultancies : Aerospace & Architectural Consultants

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Tanking is a general term used to describe many different techniques of attempting to water/damp proof walls.

The only way to permanently get rid of dampness is, firstly, to ensure that any water is diverted away from the building by draining the surrounding land and then to ensure that the walls are able to have a free passage of air on both sides, known as breathing. This breathing is not to be confused with internal to the room ventilation which while necessary for the removal of humidity within a room and is also a requirement for the breathing of a wall is not the full picture of wall breathing.

  1. The application of waterproof cement to the interior (and sometimes the exterior as well) has never in my experience been a long term and definitely not permanent solution to dampness in old buildings. I have seen this on my own sites and have many satisfied clients who removed this cement plaster and replaced it with Lime pointing and diversion of external water.
  2. The application of high tech chemicals such as Epoxy Resins which are used to build modern aircraft, Formula 1 racing cars, skis etc. are far from a permanent solution. These materials depend of a strong chemical, physical and mechanical bond to the wall and invariably fail locally which allows the ingress of moisture eventually to the whole of the wall.
  3. Dry lining a wall with battens and plasterboard (Gypsum board) seldom hides dampness for more than a season.
  4. The injection of a Silicone damp proof course which cannot be described in any way as tanking but is by some “quick Buck” salesmen is to be avoided in most cases my opinion
  5. The removal of some stone at regular intervals along the base of a wall and its replacement with a breathing and absorbent brick by itself or as part of a tanking process is in my experience not a permanent cure for dampness in stone walls. I think that any short term improvement in dampness seen by the insertion of these bricks could have more easily and more cheaply been achieved by other methods.
  6. The installation of a “cavity drainage membrane system” is probably the most expensive of the non-permanent solutions to damp walls and is the only method of tanking that I would consider. It consists of attaching a corrugated or dimpled continuous thick high density polyethylene (plastic) sheet or polypropylene mesh (plastic) to the walls using screws which forms a cavity between it and the wall. This cavity should preferably be ventilated. This plastic membrane is usually covered with studding and plasterboard or plywood and some versions can be directly plastered using modern plasters. The moisture in the walls is still there and an internal drainage system also needs to be installed, ideally with a sump and a sump (electrically operated) pump with an outlet to outside and distant from the building. Thermal insulation and sound proofing of the walls also need to be considered.

 

There are government standards covering water proofing systems for basements and the at least the following Building Regulations are applicable :

“Part L” : concerning thermal insulation
“Part E” : concerning sound insulation
“Part F” :  concerning ventilation