External Surface Coating to a Weathered Elevation

A weathered elevation usually arrives with more than one thing wrong. The existing coating is chalking or flaking, there is organic growth on the shaded side, and there are often patches of persistent darkness that indicate the wall is staying wet. The important part of this job happens before any material is chosen: working out whether the wall is wet because of the coating, or wet because of a defective gutter, a leaking downpipe or a bridged damp proof course. Coating over an unresolved defect buys a season and then fails the same way.

The existing coating is assessed and anything loose, flaking or powdering is removed. Moss, algae and lichen are cleaned off and treated rather than brushed away, because organic growth will otherwise come back through the new coating. Cracks and defects are cut out and made good with compatible materials. Where the substrate needs it, a stabilising solution or primer is applied before the coating goes on.

The coating system is chosen for the wall in front of us. Where the construction is solid-walled and needs to release moisture vapour, a vapour-permeable system is specified, because sealing a wall like that with a film-forming coating causes blistering, internal damp and in a hard winter frost damage to the masonry itself. Texture is chosen with maintenance in mind as well as appearance: heavier textures hide surface irregularity well but hold dirt more readily on a north-facing wall that stays damp.

A sound, consistent, correctly specified finish across the elevation, with the cause of any damp identified and raised rather than covered over. Where a defect such as a failing gutter or downpipe is found, it is reported before coating rather than after.