Drying Times & Guide For Treatment Of Rising Damp
1. Remove existing skirting boards and set aside for re-use where sound. Skirting’s may be unavoidably damaged in the process of removal and where this occurs we do not accept responsibility. It is highly probable that sections of skirting may be found to be affected on the reverse side by fungal decay which can’t always be detected at the time of the survey. Any replacement found necessary in this case may be charged as an additional cost. Existing plaster must be removed to 900mm above internal floor level.
2. The appropriate brick course is drilled and injected with a silicone cream or injection mortar. The corresponding external course is also injected where the wall is of two bonded leaves (where the wall is of cavity construction the outer leaf will be injected 150mm above external ground level). Vertical barriers are also installed to prevent moisture ingress from untreated walls such as adjoining properties or inaccessible areas.
3. We recommend only the use of premixed bagged water and salt resistant renovating plaster such as the tilcon limelite system (or a render sand and cement and skimming plaster system) and alternatively thistle Dri Coat render with Thistle Multi- Finish skimming plaster. Plaster must be applied as per the manufacturer’s instructions. Gypsum based lightweight plasters must not be used unless a membrane system is in place. Plasters must not bridge the dpc and must not come in contact with solid floors. A minimum gap of 2”/50 mm should be left between the floor and the plaster.
4. The walls are finished with a multi finish to a smooth even surface and not over polished.
5. Drill holes are plugged or filled with a sand and cement to the outsides. In some instances injection can be from one side only especially in listed buildings where external drill holes are undesirable.
6. Party walls-chimney breasts: The party wall act requires neighbouring owners to be notified of works to be undertaken to or affecting the party wall. Clients should undertake this prior to commencement of works. Chimney breasts- interstitial condensation can arise from burning of fuels or previously burnt fuel deposits which can cause tar deposits to leach out through plaster finishes. The inside of the chimney breast may be built upon or contain a hearth lacking an effective damp proof membrane thus lateral dampness may also occur. Rain may penetrate from open chimney pots or stacks. Clients are advised that the guarantee for rising dampness will not apply to chimney breast.
General points should be noted:
The drying out times on completion of the work any re-plastering will be the characteristic of pink, cream or grey in colour of finishing plaster. There is still a lot of moisture left within these walls and they must be allowed to dry out before any redecoration is undertaken. After about four weeks a non alkali (trade) water based emulsion paint (NON VINYL) may be applied. Redecoration with wallpaper and all other types of paints and finishes should only be carried out when the walls are dried out completely. The following drying times are approximate and are for guidance only. In general allow one month per 1”/25 mm of wall thickness.
Wall Thickness Drying Out Time
Less than 100 mm to 300 mm | 3 to 6 months
100 mm to 300 mm | 6 to 12 months
Over 300 mm | 1 month per 25mm
Where ground levels permits sufficient clearance in non-cavity walls the damp proof course may be installed below timber floors, where these are not independently supported on sub floor walls, clients are advised that all floors coverings and furniture must be removed to at least six feet away from the areas to be treated.
Every care is taken to minimise inconvenience but it should be realised that the work involves a great deal of disturbance and creation of dust (some of which may linger for a while after completion). Health and safety advice will be given verbally or in writing prior to execution of the works. A supply of water and electricity is required on site.
Quotation assumes an existing plaster thickness of not more than 25mm (1inch). If after plaster removal the thickness is found to exceed this then additional dubbing out coats of rendering would be needed to bring the new plaster up to the level of the existing plaster. Additional re-plastering at the time of surveying / inspection it may not be possible to ascertain the full extent of the re-plastering required as the presence of salts may only become apparent after the damp proof course has been installed and drying out is complete. It is required that the client complies with the drying times on walls which have been re-plastered.
After the drying out time if evidence of salting is seen on walls where re-plastering has not been carried out then this may indicate contamination by water-attacking salts and the client should contact watertight home’s to arrange a further inspection to see whether additional work is necessary. This will increase the time required to complete the work and will involve the supply of extra materials.
Watertight home’s reserve the right to make an additional charge for the extra thickness required.
Calculated on a pro-rata basis from the original quotation. Following Treatments during the anticipated drying out period, walls treated for rising dampness may experience the sudden or gradual re appearance of damp patches which will then dry out.
Water staining such as this is usual and not a sign the work has been ineffective. No inspection under guarantee will be made during the anticipated drying out period.