by LCL »
Mon Feb 04, 2008 7:09 pm
leeanne.reed
Your note mentions two very important factors. 1. Solid wall and 2. Cement.
Old solid walls are designed so that the outer section of wall becomes wet during bad weather which then evapourates when the air pressure outside is less than that of the inside. The application of a cement render is preventing any such evaporation occuring. Some might say; but if it stops water getting out, why has it not stopped it getting into the brickwork. There are a number of reasons for this.
1. Inherent moisture in the wall when the cement render was applied externally.
2. Fine cracks in the render offer a point for moisture to get in and
3. Moisture vapour from cooking, inhabitants etc will migrate to cooler areas by natural convection. Solid walls are such cooler areas and can attrach the moisture vapour from inside the property.
The issue could also be due to a plumbing defect or penetrating damp from say a dripping gutter.
I would suggest the render is hacked off externally and internally, preferably in summer of after a few warm weeks with no rain. Leave the outside for as long as possible, saturated masonry takes about a day / mm to dry out properly. Re-render the external wall with a lime:sand mixture. No cement what so ever. Re-finish inside with a lime : sand render with a skim finish. This should allow the wall to adequately breathe.
Dampness in old properties needs to be managed, not cured. Some will say to install a chemical DPC. These are very, very rarely required. They often rely on a waterproof internal render, and hence such 'guarantees' are not normally available without the 'special render', I wonder why???
Hope this helps.
LCL