Damp Proofing Methods:
For a long time now the chemical damp proof course has been seen as the cure for all damp problems. At Maclennan we specify and carry out work on a whole range of buildings. Many of them are traditional built buildings of cob and stone or flint and brick. For these buildings a chemical damp proof course is not suitable.
We might recommend the removal of sand cement renders and replacement with a lime render which will allow the walls to breathe and shed moisture, before considering this read our advice on damp and lime render click here for PDF article on this subject.
Lime Mortar for damp proofing.
MacLennan do have lime mortars that are damp resistant and are suitable for use on walls which are damp but where the cause of the damp has been cured. MacLennan lime plasterers have 20 years of experience with lime mortars and where they are suitable we will specify lime mortar for Historic buildings or buildings that need to “breathe”
For buildings built with walls thicker than 400mm or of chalk, cob, flint or friable stone we would recommend ventilated cavity plaster lath..
Ventilated cavity laths allow buildings to ‘breathe' by letting moisture vapour escape from the surface of the wall through a continuous air gap. They are a form of dry lining but as they are not made of a bio degradable material such as wood or paper ( on plasterboard ) they cannot decay and will last the lifetime of the building. The inside of the property is left completely dry and warmer while the structure is breathing as it should do.
There are a range of finishes that can be applied over the membranes. Maclennan plaster over with lime mortar plasters, High Impact one coat plaster and plasterboard adhered to the membrane, so as once plastered you would not know the wall had been lined. We would not normally install a dpc as they are not very effective in this type or thickness of wall. Re-plastering has to be carried out with dpc injection to complete the damp proofing, The recommended plaster is a strong cement render which is not suitable for chalk or soft friable stone.
‘If dpc injection is to be installed in a thick stone wall then grouting or injection mortar would have to be considered.’