How to soft wash slippery & rotting wood/timber/composite (plastic) decking

November 17, 2023

How to soft wash slippery & rotting wood/timber/composite (plastic) decking

Slippery decking can be dangerous as well as unsightly.
It can become covered with biological growths, especially algae, on which people can slip and break bones.

And of course it is simply unpleasant to sit out on a filthy, mouldy, rotting decking which was originally erected to be a joy, not an eyesore.

Soft washing wood decking and other wooden buildings and fences is a huge market for soft washing contractors

A light power wash to remove the worst of the algae, followed by a treatment of Benz Bio Cleanze will give neglected decking a new lease of life.

If you can't get hold of a power washer, a simple watering can and stiff brush to clean off the algae will work wonders.

  • No more slippery decking
  • No more unsightly staining

Quick tip: Although a light power wash or scrub will improve the appearance of decking, the algae spores will not be killed and will quickly regrow. So it's essential to follow up asap with a treatment of Benz Bio Cleanze. The biocide acts in a similar way to sterilising a babies bottle, ensuring the spores of the biological growths are killed.

This means the decking will remain clean for a considerable time, especially as Bio Cleanze offers long-term residual protection against re-colonisation by algae spores.

A routine application every 6-18 months of Bio Cleanze on bare timber decking will keep it looking great. Although all timber is different it will probably fade to a natural grey-silver colour.

Can Lightning Cleanze be used on decking?

When it comes to soft washing timber, there's an exception where Benz Lightning Cleanze can be the ideal choice. This exception arises in "rescue" cleans where the timber has been neglected for years. This makes the use of Lightning Cleanze an excellent option because the the heavy damp biofilm acts to protect the wood from any negative effects from the chemical treatment.

Additionally, if your customer values faster results than Bio Cleanze alone can offer, Benz Lightning Cleanze comes into its own.

Watch the short video below to see Lightning Cleanze rescue this heavily colonised timber decking:

Quick tip: Scroll down this page to the section titled "Further Principles for Soft Washing Wood/Timber" to read our more detailed advice regarding using Lightning Cleanze to soft wash wood decking.

Below is an example of neglected timber decking that would benefit from soft washing with Lightning Cleanze.

How to clean timber decking softwashing

Below is the same decking after we gave it a Lightning Cleanze treatment and a light pressure wash

how to softwash timber decking to clean

Quick tip:
Before applying Lightning Cleanze to any wood surface, we strongly recommend thoroughly rinsing the surface or giving it a light pressure wash. After Lightning Cleanze has completed its work, immediately rinse the area again to minimize the potential of chlorine damage to the wood.

In some cases (such as seen in the video above) pre-cleaning by pressure washing, or thorough rinsing, may be too time-consuming, costly or impractical. In such situations Lightning Cleanze can become the most suitable product for initial soft washing. However, it is important to maintain the decking with regular treatments of Bio Cleanze.

By considering these factors and following the recommended steps, you can make the most of Benz Lightning Cleanze to ensure optimal results while preserving the timber.

Can decking be stained, oiled or varnished after treating with Bio Cleanze?

Wood decking, and other external wooden structures, will be ok to stain, oil or varnish once completely dried out.

Bio Cleanze can be used to maintain decking after staining or oiling but will only be able to treat the surface colonisation. This is because the oil staining will hinder the product from penetrating so deeply into the wood.

Quick tip: It is highly likely that water-based stains probably will not inhibit the penetration of Bio Cleanze, although we have no real-world data on this.

Varnishing, and similar non-breathable sealers, will prevent Bio Cleanze from penetrating below the surface. It will still treat any surface colonisation but long-term residual protection from re-colonisation will be lost

In our experience we've found that in many instances the best way to maintain timber decking, wooden buildings and wooden fences is to never treat them with oil, varnish, or paint. Simply using Bio Cleanze is often more effective and we believe most of your customers will enjoy the results far more over the long-term.

Benz Bio Cleanze helps protect wood from wet and dry rot

The active ingredient in Bio Cleanze is used in commercial wood preservative products and processes. And in our experience, following up the first treatment with 6-24 month applications (time scale depends on the local environment) will significantly help prevent wet and dry rot.

Other timber structures such as timber sheds and wood fencing can be similarly treated to improve their appearance and help extend their life.

Children & animal safety: If wood decking or other wooden structures are to be used by children or animals apply Bio Cleanze at a maximum dilution of 50:1. Following a treatment, ensure all surfaces have completely dried out before allowing children and animals access to them.

General principles for soft washing wood/timber

We recommend using Bio Cleanze for soft washing wood whenever possible. And of course, even when confronted with extremely bad colonisation customers will expect it to be cleaned reasonably quickly.

For such surfaces, and customer expectations, we suggest using Benz Lightning Cleanze first, at the lowest viable dilution, for the shortest viable contact time.

It is important to pre-soak the wood to keep the chemical on the surface, which will enable it to clear the worst of the colonisation without harming the wood.

What we do NOT endorse when using Lightning Cleanze to soft wash wood:

  • Using at an unnecessarily high-strength.
  • Not pre-soaking the wood the wood before treating.
  • Leaving on the surface for unnecessarily long periods of time.
  • Using power washers at high pressure to rinse.

Used responsibly and with care Lightning Cleanze – with light pressure washing – can be a helpful adjunctive product to rapidly remove heavy colonisation from wood surfaces that is the result of years of neglect.

After thoroughly rinsing Lightning Cleanze from the surface, complete the job with a treatment of Bio Cleanze and continue ongoing maintenance with Bio Cleanze only.


How to soft wash composite (plastic) decking

Do not use steam cleaning unless you are absolutely certain that it won't damage the decking, because epoxy (part of the composition of some composite decking materials) can be adversely affected at temperatures as low as 60 degrees C.

Use Benz Lightning Cleanze for the first clean (5-10:1 depending on the severity of the contamination).

Then spray with Benz Bio Cleanze at 50:1 for your ongoing "Clean & Maintain" service (6-18 months depending on the local environment).


We hope this information is helpful and sincerely wish you great success in your soft washing business,

Benz Team

Click here to get more practical soft washing how-to tips

How to find answers to most soft washing questions: Simply enter a relevant "keyword" or short phrase – e.g. keyword for the above link = "how-to" – into our in-site Search Engine (magnifying glass icon on the main menu).

Order Benz Softwash chemicals & equipment online or by phone:

GB (England, Scotland, Wales)

Phone: 0800 70 74 222 


Ireland and other countries

Phone: 00353 214 622 978


Lines open Monday - Friday, 9am – 5pm

Please note: The above numbers are for orders only (click here for tech support)

PS: Click here to set up your "Clean & Maintain" programme
. After completing an initial soft wash treatment, put your customer on a "Clean & Maintain" ongoing maintenance programme. Your customers will enjoy a permanently clean property and you will enjoy a steady stream of repeat business.

This is clearly a win-win arrangement for you and your customers.


Click here to explore the extensive range of Benz softwash cleaning chemicals & equipment

Benz Softwash Bio Cleanze DDAC biocide & Benz Softwash Lightning Cleanze SH sodium hypochlorite biocide

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