Sodium hypochlorite is the active ingredient behind most professional softwashing solutions, but the concentration and handling make all the difference between an effective, safe clean and a botched one that scorches the lawn and leaves streaking behind. It's the same basic chemical as household bleach, at a different concentration and applied with a very different process.
This guide explains the dilution ranges professionals actually work with, how plants get protected during application, and why neutralising the surface afterwards is a step that shouldn't be skipped.
Dilution ranges in professional use
Professional softwashing typically uses sodium hypochlorite diluted down significantly from the concentrated bulk product, with the exact ratio depending on the surface, the severity of algae or moss growth, and the specific product being used. This is quite different from grabbing a bottle of household bleach off the shelf and spraying it neat, which is both less effective for dwell-based treatment and more likely to damage surfaces and plants.
Getting dilution wrong in either direction causes problems: too weak and the treatment doesn't kill growth at the root, meaning regrowth within weeks; too strong and the risk of surface damage, plant harm, and unpleasant fumes during application all increase. Getting it right consistently across a whole job is a skill built up over repeated use, not something a single online guide can fully substitute for.
Protecting plants during application
Before softwashing near borders, hedges or lawns, professional practice is to thoroughly wet down nearby plants with plain water first, which dilutes any overspray that lands on foliage, and to physically cover the most vulnerable plants with sheeting where practical. Working methodically and avoiding overspray in windy conditions matters too, since drift can carry solution further than intended.
After application, plants are typically rinsed again with plain water to wash off any residue, which significantly reduces the risk of leaf scorch compared with leaving the solution to dry on foliage.
Why neutralising the surface matters
After the biocide solution has done its work and been rinsed, some professionals apply a neutralising rinse, particularly on surfaces feeding into water butts, ponds, or sensitive drainage, to reduce residual chemical activity. This step isn't always necessary for every job, but it's worth asking about if you have a water butt connected to your gutters or a garden pond nearby.
Skipping proper rinsing altogether, rather than neutralising specifically, is the bigger issue in most botched DIY attempts, since solution left to dry on a surface can leave a white, powdery residue or uneven staining.
Why this is best left to professionals
Getting dilution, application method, plant protection and rinsing all right at the same time is a lot to manage correctly on a DIY basis, and the margin for a costly mistake, scorched plants, streaky results, or surface damage, is real. Professional softwash treatments typically cost around £250-£450 for an average house exterior, a reasonable cost for a job that's genuinely easy to get wrong without training.
There's also a personal protective equipment side that's easy to underestimate: gloves, eye protection, and in some cases a respirator are standard for anyone handling concentrated sodium hypochlorite, along with knowing how to store and transport it safely. A trained professional arrives with all of this as routine, rather than it being an afterthought bought at the last minute for a one-off DIY job.
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