So you have identified and confirmed that the issue is Rising Damp – What next? Tech-Dry have a brand of DIY Damp course solutions which will enable you to treat Rising Damp. Following we detail the necessary steps to assist you with this task.
Please note however, the DIY option is most cost effective and suitable for small areas only. Where you are seeking treatment for a whole house or the wall has been badly damaged by salt attack or is heritage listed we would always recommend seeking an experienced, licenced contractor to undertake the work.
The main and most widely accepted option to treat Rising Damp is the insertion of a new impervious damp proof course into the base of the wall.
One accepted method of doing this in Australia is chemical injection of a damp course liquid or cream through a series of holes drilled at the base of the wall to form a damp proof barrier. This is especially suitable for building owners or contractors with small jobs; a few metres of a wall or a brick fireplace.
Purchase some a Tech-Dry Damp course suitable to treat Rising Damp. We would recommend the use of the Tech-Dry damp course cream (DPC). It is user friendly, water-based and cost effective.
Where treating internally carefully remove any skirting boards to reveal the lowest mortar course just above the floor level.
If treating the external part of the wall, locate a mortar course 150mm above the ground level or just above the internal floor level.
Mark holes at approx. 80mm apart in the mortar bed. Avoid drilling holes directly above the vertical mortar joints of brick walls.
Set the drilling depth to 10mm less than the wall thickness. Drill 12mm holes into the mortar bed using a hammer drill.
Remove all dust from the holes using a vacuum cleaner. It is important that no drill dust is left in the holes.
Inject DPC Cream into each hole using a standard caulking gun. Ensure the holes are filled fully with the cream and avoid any bubbles or hollows when filling.
The cream in the holes may take up to 24 hours or more to be fully absorbed by the mortar bed and bricks. After the cream has been absorbed there should be a continuous wet mark in the treated mortar and bricks above and below the treated mortar bed. If the penetration is not evident and/or has not reached the mortar in the middle of the two holes a second fill of the DPC cream may be required.
The final and probably most important step involves the gradual desalination of the wall, where the salts and moisture that are trapped within the wall have time to evaporate to the surface.
This normally takes between three and six months and we would recommend leaving the existing affected plaster / render / mortar on during this time.
Once the dry out period has passed this damaged plaster / render can be removed. We recommend removing approx. 300mm above the highest level of damp recorded and it must be removed all the way back to the stone/brick.
A new salt retardant plaster / render can then be applied to the wall ensuring not to cover/ bridge the new damp proof course. A small gap at the base of the internal plaster / external plaster must be left to protect the damp proof course. Skirtings can be replaced however to cover this gap in the plaster work.
It is important to use a cement / sand render with salt retarding admixture in the mix.
It is also recommended after this dry out period that any loose and affected mortar is also removed. This must be replaced with a soft lime mortar. (Please see notes on residual salts)
Once the plaster / render / mortar has been replaced and dried any decorating of these areas such as painting, wall papering can be undertaken.
Note: Residual Salts
It is important to note that there may be situations where small traces of hygroscopic salts will remain in the wall despite removal efforts. These salts in some instances can bleed out into new plaster / render / mortar. These salts are not an indication that the treatment has not been successful. Further maintenance on these areas may be required in the future.