Moisture in the base of wall is drawn up capillaries within the fabric of the masonry usually to a height determined by the evaporation process of the wall i.e. dense renders can restrict evaporation resulting in rising dampness exceeding 1m. Salts from the ground usually chlorides and nitrates which are hygroscopic are carried up wall into plaster thus a specialist salt resistant plaster should be used to prevent salts from migrating into surface plaster causing further damp problems.
We insert two types of chemical damp proof course depending of construction of walls. (1) Water based siliconate low pressure injection. (2) A silicone based cream injected into the masonry.
A chemical damp proof course involves the drilling of a series of holes usually at the base of the walls to be injected. Drilling will be from whichever side is more practicable and as indicated on plan. Clients are required, prior to the arrival of the technicians, to provide free access to all walls being treated internally by removing skirting boards, fittings, furniture and carpets, and any other obstructions that may hinder treatments including access to ground area adjacent to all external walls that have to be treated, therefore all external obstructions including vegetation on direct contact and this maybe unavoidable during the course of the treatments.
2. Abutting Structures
Vertical rows of holes will be drilled as necessary and injected for the purpose of isolating abutting structures to avoid bridging the new damp proof course.
3. Varying (floor) Levels
The damp course will normally be inserted some 50 -150mm above the finished floor or the external earth or floor levels, whichever is the higher. Areas of walling against higher ground may be affected by lateral penetration of dampness and clients are advised to have the higher ground lowered to below damp course level or alternatively to have these areas treated by a suitable tanking / waterproofing system.
4. Electric Power
Clients are required to provide electric power, minimum 10 amp x 240 or 110 volt supply, together with normal lighting facilities where necessary. Where power is not available a portable generator will be supplied at an extra charge.
5. Drying Out
The drying out periods after the installation of a damp proof course can vary considerably. However, as a guide, it is estimated that it takes one month for each 25mm of wall thickness. The drying out can be influenced greatly by heating, ventilation, and the condition of both internal plasters and the external walling. Clients should bear in mind that penetrating dampness can also be present in the walls caused by absorbent materials, faulty pointing, or external rendering and damaged rainwater goods. Dampness can also affect the internal surfaces of walls caused by condensation. Such defects should be attended to without delay as our rising damp treatments will have no effect on any other dampness other than dampness rising from the ground into the base of the walls.
Walls may have to be left exposed for up to a period of 14 days prior to re-plastering to let initial drying out to take place. This will vary as to the degree of dampness by which they are affected. Great care should be taken to ensure that salt affected plaster does not harm future decorations. One of the following recommendations should be closely followed:
Where the existing plaster is soft, porous, loose or hollow sounding it should be immediately removed up to a level of 1m or 300mm above moisture level which ever is greater.
Damp plaster may not always be unsound. If it is firm to the touch it may be allowed to remain for approximately 12 months. It is essential that all wallpaper be removed from affected walls and decoration be confined to a water bound matt emulsion paint for a period of up to two years. Re-plastering must always be carried out using a salt resistant renovation plaster.
It is recommended that plaster is renewed after damp proof injection with a suitable plaster / render. In some cases it may be an advantage to delay plastering and allow wall to dry out, the true extent of the dampness caused by hygroscopic moisture can be more easily established and it may be possible to restrict the extent of re-plastering the client should appreciate that the need for re-plastering may ultimately be required in the future and decoration should be regarded as temporary.
Clients are strongly recommended not to apply permanent decorations such as wallpaper or gloss paints. A suitable emulsion paint should be used for a period to allow moisture in the wall to evaporate from within the wall.
8. All fluids supplied by Tay Property Services Ltd are approved by the British Wood Preserving and Damp Proofing association.