What causes Rising Damp?
Rising damp occurs when the ground moisture (containing mineral salts), is allowed to rise up the walls by capillary action via the pores in the bricks and mortar joints. This happens where no barrier i.e. damp proof course (DPC) exists. Sometimes the exterior ground levels have built up and bridged the original DPC, and is also found when the existing DPC is ageing and losing efficiency, as many older buildings used brittle materials such as slate to provide DPC.
What is rising damp? Watch our video..
Why is Rising Damp a problem?
Rising damp can be damaging to the structure of the buildings brickwork, pointing, external rendering, internal plaster, decorations and abutting or embedded timbers, such as wall plates, joists, skirting and floor boards.
It can also be detrimental to the health of the occupants, causing respiratory problems.
How would DrySide rectify the problem?
After the installation of a remedial DPC, the residual moisture will evaporate generally to the inside surfaces of the walls, leaving any concentrations of mineral salts on or near to these surfaces. To control these mineral salts, some of which are hygroscopic (attracts moisture from the air), we recommend the walls be replastered to a salt-retardant specification.
– Inspection & Surveys
The correct identification of the causes of damp within a property is fundamental to providing the correct rectification methods and specifications. We believe that the eye of experience when assessing a building is invaluable and a crucial part of the diagnostic procedure. We also use moisture meters (resistance or capacitance based) to provide a profile or pattern of moisture meter reading (without significant damage to the existing decorations) to assist and confirm our visual observations. Our surveyors endeavour to identify contributing factors such as defects to rainwater goods, external ground levels, condition of the external rendering or pointing to the brickwork, condensation and air flow within the building, in relation to the use of the building and the materials used for construction and decoration.
– DrySide Surveys
DrySide carries out inspections according to your instructions on properties in relation to basement waterproofing and rising damp, as well as timber defects, such as infestations by wood-boring beetle (woodworm) and decay such as Wet Rot and Dry Rot. The purpose of our inspection is to provide a report with justification, specification and quotation for our proposed works and treatments.
The inspection is carried out by specialist qualified staff holding Certified Remedial Treatment Surveyor (CSRT), Certified Surveyor for Structural Waterproofing (CSSW), as recognised by the British Wood Preserving and Damp Proofing Association. Additionally they have passed the examinations of the School of Waterproofing, as well as many manufacturer’s exams and training courses.
Our senior surveyor alone has over 26 years surveying experience. DrySide offers an honest, balanced and informed opinion, which is not restricted to any single manufacturer or pay-related bonus/commission scheme, thereby enabling us to provide our clients with a reliable report, giving justification for our works, identifying the extent of such work and the proposed specifications, with a realistic quotation in relation to your instructions.
Client’s Responsibility: Prior to our arrival, all fixtures, fittings, furniture, effects, carpets, and floor coverings must be removed and protected/covered to provide clear working access of at least 1.5m. The owners of any adjoining properties’ party wall must have given permission for the works to proceed.
To control rising damp, we propose to use the Dryzone/Drytech chemical damp proofing system. This process recommends that the existing wall plaster is removed to the specified areas (this may be carried out by your own contractor prior to our arrival). A series of 12mm diameter holes will be drilled at predetermined horizontal centres to the correct depth into the mortar joint, and water-repellent cream is injected into the holes. On completion of the aforementioned works, the holes can be plugged, pointed over, or plastered over to our specification.
– Replastering (ideally by DrySide Ltd.)
Replastering subsequent to our Damp Proof Course (DPC) installation is an integral part of the chemical damp proofing system. The importance of compliance with our replastering specification cannot be stressed enough. Water rising from the ground contains mineral salts (chlorides, nitrates, sulphates, etc.). These mineral salts are hygroscopic and can attract moisture from the atmosphere. Replastering to our specification is designed to contain these salts within the body of the wall, whilst providing a vapour-permeable finish to enable the drying out of the residual moisture within the wall. The installation of the DrySide chemical DPC alone will not control all of the effects of rising damp or the effects of salt contamination to the existing wall plasters.
– Skirting boards and Architraves
The existing skirting boards and architraves, when in contact with damp walls, become brittle and weakened or decayed and are likely to be damaged on removal. We cannot accept any claim for such damage. Refitting of the original or new should be delayed until the initial moisture has evaporated (usually a couple of weeks) and only suitably primed timbers should be used. The refitting or renewal of these timbers has not been allowed for within our quotations, unless stated otherwise.
Initial redecoration may be carried out as soon as the initial drying out of the moisture has occurred (usually two to four weeks), but only trade emulsion paints should be used. Permanent decoration should be delayed until the final drying out has occurred. This may take one year following replastering and even then the use of impermeable coverings and paint is not recommended. The B.R.E. (Building Research Establishment) Digest 245 states that for every 25mm thickness of wall, at least 1 month should be allowed for the drying out of residual moisture.
Please be advised that our proposed works can generate a considerable amount of noise and dust. Naturally, we will try to keep these disturbances to a minimum, but despite our best endeavours, some dust will travel throughout the property to untreated areas, and some additional cleaning will be necessary under a separate contract. This has not been allowed for within our quotation.
Replastering subsequent to our Chemical Damp Proof Course (DPC) installation is an integral part of our damp proofing system. The importance of compliance with this replastering specification cannot be stressed enough. Water rising from the ground contains mineral salts (chlorides, nitrates, sulphates, etc.); these mineral salts are hygroscopic and can attract moisture from the atmosphere. The installation of any chemical DPC alone is unlikely to control the effects of rising damp or the salt contamination of the existing wall plasters. For this reason we always recommend the treated walls be replastered to the following specification:
• Remove all traces of the existing wall plaster to the specified area.
• Remove embedded timber fixing grounds and make good voids.
• Apply render coat(s) each to a thickness between 8 to 14mm to provide a minimum coverage of approximately 18mm to walls, comprising of:-
• 3 Parts washed sharp sand (BS 1199 Table 1 Grade A or BS882 Table 5 Grade M) to 1 Part cement (Fresh free-flowing OPC BS12 or sulphate-resisting cement BS4027) using a salt retardant/waterproofing additive in the gauging water to the manufacturers’ quantities. These components must be thoroughly mixed together.
• Additional render coats to “dub out” (extra thickness) should be to the same specification and applied before the previous coat has finally set.
• Apply finish plaster (multi-finish) to a nominal thickness of 3mm.
• A gap should be left between solid-type floors and the render coats/finish plasters.
The refitting of the original or new skirting boards (primed) should be delayed until the walls have dried sufficiently and has NOT been allowed for within our quotations, unless otherwise stated.
Decoration should be delayed (usually two to four weeks) to allow the initial moisture to dry out. At that time, we recommend that only trade or contract emulsion paints be used. Final decoration should be carried out only when the wall has fully dried out. This may take six to twelve months. Even then, we do not recommend the use of vinyl paints or papers or other impermeable coatings and decorations, which may act as a vapour barrier and prevent the walls from breathing and drying out fully.
DO NOT USE GYPSUM-BASED PLASTERS, INCLUDING CARLITE & BROWNING. NOT EVEN FOR FIXING ANGLE BEADS, MAKING GOOD OR DUBBING OUT.
Hacking off wall plaster produces a large amount of dust, and replastering being a wet trade, some spillage and droppings often occur, despite our best endeavours. It is important that adequate protection is in place prior to our arrival. It may be necessary for additional cleaning to be carried out following our works, not just to the areas of our works but to other areas within the property. This additional cleaning has not been allowed for within our contract.
It is important that the property is regularly and correctly maintained. Particular attention should be given to rainwater goods, internal and external plumbing, ground levels, condensation, pointing, rendering, roofs, window sills, etc.