How to clean timber and softwood cladding

Why pressure is the wrong tool for softwood

Softwood has soft summer growth between harder rings. A pressure jet cuts the soft wood away faster than the hard, leaving a furry, ridged surface where the grain has been raised. That raised grain looks worse than the growth did, holds even more moisture, and gives the next colony of algae a perfect foothold. It can also force water behind the boards and strip any stain or oil finish in patches. Once the grain is raised there is no rinsing it flat again; it needs sanding. So on timber cladding we avoid pressure entirely.

This guide sits under our Wall Cleaning & Softwash work, covering 20-mile radius of Plymouth.

What we use instead

Cladding takes a weaker treatment mix than render or masonry, applied at low pressure so the product lands on the boards rather than being driven into them. The treatment is given time to work on the growth, then the surface is gently rinsed. It is the same softwash principle we use on walls, turned down to suit a material that is far easier to damage. Where growth is heavy and established, the honest answer is sometimes that it lightens further over the following weeks as the dead growth weathers away, rather than disappearing in one afternoon.

Where the growth actually starts

Look at the bottom edge of each board, the overlap on shiplap or feather-edge, and any horizontal trim or window sill that catches run-off. Those are the permanently damp lines. North-facing elevations, cladding near hedges or trees, and boards close to the ground where splash-back keeps them wet will always go first. Understanding that tells you something useful about maintenance: the aim is to keep those damp lines from establishing, not to scrub whole faces that were never the problem.

Protecting what is around it

Timber cladding is often next to planting, decking or a doorstep, and a treatment that is fine on a board is not something you want pooling on a lawn. Timber decking or a doorstep directly under the work is covered rather than rinsed afterwards, and planting is protected before anything is applied. If there are areas of cladding or timber detail you would rather we left alone, for example a newly stained section or a feature board, tell us at quoting stage so it is written into the scope.

Treated, stained and painted boards

Stained or oiled boards are cleaned with the same gentle approach, but a clean will show up any finish that has already failed: patches that were protected by the dirt suddenly look pale next to bare timber. That is worth knowing if you are planning to re-stain, because cleaning first gives the new finish a sound surface to bond to. Painted boards behave more like painted render and tolerate the treatment well, though flaking paint will lift if it was already loose.

Composite and uPVC are different jobs

Not every clad wall is timber. Composite boards and uPVC cladding look similar from the road but behave differently, and each has its own guide on this site. If you are not sure which you have, a close-up photograph of a board end usually settles it.