Sandstone cleaning and sealing in Narraweena

A typical Narraweena property has its sandstone working hard: retaining walls cutting the slope into usable levels, steps linking them, and a front fence or entry wall facing the street. Retaining walls are usually where the problems concentrate. The base stays damp and green, the face carries white salt and rusty streaks from water seeping through, and the joints fill with moss. Steps in shade grow black mould. The front fence, by contrast, tends to carry dust and lichen. Our technicians look at all of these before starting and try the mildest cleaner that works on each, so nothing is cleaned harder than it needs to be.

Biological growth is killed with a biocide made for porous stone and left to dwell, then brushed off and rinsed gently. Salt bloom on retaining walls is swept away dry first. Rust streaks are tested with an iron-stain treatment on a small area, as results depend on how deep they run. We do not use acid, which can create more iron staining in Sydney sandstone, or a turbo tip, which scars the surface. On sloping blocks, wash water is held at each level with bunds and lifted out by wet vacuum, so none of it heads down the driveway to the street. Walls are checked for movement before work begins.

Most retaining walls in Narraweena are best left unsealed. They hold back soil and groundwater, and that moisture needs to escape through the face; a sealer would trap it and cause flaking. Steps, paving, wall caps and front fences that dry well are a different story, and a breathable impregnator keeps grime and growth from settling in as quickly. It goes on only when the stone is dry, in thin coats with no surface film, after you have seen natural and enhancing samples. We note what was used and suggest a maintenance clean every few years, sooner for shaded steps that see little sun.