Background

This victorian semi-detached property in West Sussex was suffering from damp patches and salt-contamination on the walls of its street-facing living room. The building’s construction consists of solid brick walls with an exterior render and weatherproof coating applied externally.

The walls of the living room had previously been treated for rising damp by a contractor. This included the installation of a chemical damp-proof course and replastering of the affected areas up to 1 meter height using a sand and cement render.

A victorian property suffering from damp patches and salt-contamination.

These previously treated walls were starting to show signs of damp above the replastered area, showing peeling paint and blistering plaster. Damp-proofing experts, Surrey Hills Preservation, were called in to survey and fix the problem.

The Problem

After the survey, it was found that there were two main issues with the original damp-proofing treatment. The first issue is that an inferior damp-proof course had been installed. If a damp-proofing cream with a low level of active ingredient is used to treat rising damp then it will likely not be able to sufficiently stop the passage of moisture.

The second issue with the original treatment was the use of a sand and cement render for the replastering.

Sand and cement renders are very good at holding back groundwater salts but they are very dense and not highly breathable.

The Solution

The first action Surrey Hills Preservation took was to remove all of the sand and cement render and get back to the bare brickwork. Care need to be taken because hard renders can be difficult to remove without damaging the softer brickwork underneath.

Once the render had been removed, further investigation of the original damp-proof course drill holes revealed that they had not even been drilled to the full required depth. The original holes were re-drilled to the correct depth, so that they would be ready for retreatment.

Insert damp proofing rods

Dryrod Damp-Proofing Rods were chosen to create a properly effective damp-proof course. Their unique 100% active ingredient formulation allows the original DPC holes to be used for retreatment, something that traditional damp-proofing creams can not be used for. This negates the need to drill new holes along a separate mortar line.

Replastering

Dryzone Fast-Set Plaster was chosen as the replastering method. Dryzone Fast-Set Plaster is a highly breathable, damp-resistant and salt-resistant renovation plaster that is designed to be used on damp and salt-contaminated walls. The ready-gauged plaster was simply mixed with water before being applied in two coats by trowel, to a total thickness of 20mm. The quick 2 hour setting time of the plaster also allowed for 2 coats to be applied in one day.

Skim Coat Application

Surrey Hills Preservation then carried out a skim coat application, leaving the client with a damp-free surface, ready for decoration with a breathable paint. The Dryzone System came to the rescue of a failed job and proved that real value can be found in high performance.