What's the best way to soft wash wood decking?

June 01, 2022 2 Comments

What's the best way to soft wash wood decking?

Wood decking requires a bit of thought when it comes to advising how best to clean & maintain it. This is because the combination of methods and products used to treat the decking will affect how the wood looks.

Some people like their decking to have the grey weathered look that results from not treating the deck with an oil or water-based deck finishing product containing a UV inhibitor. But others prefer the look of finished decking.

A contractor who understands the various implications of each approach can explain them to their customers, enabling their customers to make an educated choice. 

Quick tip: We often treat very large areas of decking with Bio Cleanze alone, without applying a finishing product, because some customers can baulk at the cost of the oil and labour.

To varnish wood decking or not to varnish wood decking?

In our experience it is usually best to not varnish wood decking, because the varnish eventually breaks down from exposure to sunlight, peels off and looks awful.

And algae can grow under old varnish, which usually cannot be treated because of the varnish.

The most commonly available varnish is non-breathable and non-porous. It is possible that a breathable varnish could be used but we have no data on that at the time of writing.


Should wood decking be sealed?

The question of whether to seal wood decking is a matter of debate and personal preference. We prefer not to seal the wood but rather to give a re-treatment of Benz Bio Cleanze every 6-24 months or at the first sign of algae reappearing.

Regular treatment with Bio Cleanze imparts residual protection against re-colonisation and also helps protect against wet and dry rot (the active ingredient is used in wood preservative products).

When wood decking as been sealed, Bio Cleanze will never again be able to deeply penetrate the wood, although it will be able to deal with light surface colonisation.

How to stain wood decking?

A wood stain product that allows for continued porosity of the wood will most likely allow a biocide treatment to kill the algae.

In our experience, whenever possible the best approach is to treat wood that has not previously been stained with Bio Cleanze first, and then stain it. 

Oil-based stains will inhibit subsequent treatments of Bio Cleanze from soaking deep into the wood, although they will tend to repel water ingress, which is a plus.

Quick tip: Unlike non-breathable varnish and sealers an oil based stain will allow some penetration by Bio Cleanze. because over time oil slowly evaporates.

Water-based stains should allow Bio Cleanze to fully soak in but they can have a tendency to peel, similar to varnish.

So given that there are pros and cons for each, the choice to apply an oil or water stain is largely down to personal preference,

Click here for more detail about soft washing wood decking

Will Bio Cleanze change the colour of wood decking?

Wood decking will naturally fade and turn a light grey over time, which can be briightened using a commercially available "wood brightener".

Bio Cleanze is unlikely to change the colour of most types of wood. But always test a small area to be sure before treating the entire area of decking. 

Quick tip: Sometimes customers mistake the cleaned surface that results from soft washing with Bio Cleanze for lightening the wood. In reality, Bio Cleanze simply reveals the original colour of the wood beneath the dirt and colonisation.

Treating wood with Lightning Cleanze however, will lighten the colour. So take this into account and let your customer have full information about the possible effects of a soft wash treatment. Then they can make an informed choice about they way they prefer to have their decking treated and maintained.

Does Bio Cleanze preserve wood decking?

Sodium hypochlorite (sh, hypo) is used in paper mills to break down the fibres in wood prior to pulping it into paper. So care must be taken if treating decking with Lightning Cleanze, a sodium hypochlorite based product, to obtain a rapid result. 

Click here to learn how to use Lightning Cleanze to treat wood decking without damaging the wood

In contrast, the active ingredient in Bio Cleanze – Didecyldimethylammonium chloride (ddac) –  is used as the active ingredient in wood preservative products.

So a bonus – and an excellent selling point when you are quoting for a new job – when treating wood decking with Bio Cleanze to remove algae staining, is that it helps preserve wood from wet and dry rot.

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

Ben, Leo, Fiona, Stevie & Anthony

Click here to get more practical soft washing tips about how to treat decking

How to find answers to most soft washing questions: Simply enter a relevant "keyword" or short phrase – e.g. keyword for the above link = "decking" – 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 

Online: www.benzsoftwash.co.uk

Ireland and other countries

Phone: 00353 214 622 978

Online: www.benzsoftwash.com

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

2 Responses


May 29, 2023

Hi Rosh, thanks for your comment.

After a soft wash treatment using Bio Cleanze on your wooden deck, it’s important to allow sufficient time for the wood to dry thoroughly before applying any protective coatings. The exact drying time can vary depending on factors such as weather conditions, wood type, and the extent of moisture absorbed during the cleaning process.

As a general guideline, it is recommended to wait at least 24 to 48 hours before applying any protective coating to your wooden deck. However, it’s important to note that this is an estimate and the actual drying time can be influenced by various factors.

Additionally, ensure that the deck is exposed to adequate airflow and sunlight during the drying process, as this can help expedite the evaporation of moisture.

It’s always a good idea to consult with the professional wash company that performed the softwash treatment or follow any specific instructions provided by the coating manufacturer for the most accurate guidance tailored to your specific situation.

Btw: Please read the section in our article above headed “Should wood decking be sealed?” before deciding to seal your decking.

Rosh Kalapurathara
Rosh Kalapurathara

May 29, 2023

Hi, one of the professional wash company Softwash WD my house roof, garage roof and walls using biocleanze and the wooden deck also washed. My question is how long I need to wait to apply any protective coating to my wooden deck? Please advice.

Leave a comment

Comments will be approved before showing up. Please revisit to read our response.

Also in Benz Trade Tips

How to remove rust stains from render
How to remove rust stains from render

April 12, 2024

Rust stains on renders caused by flue pipes, satellite dishes, mild steel fixings, overflow pipes, etc, can be easily removed.

Click the link on this page to find out how ...

View full article →

Understanding the complex world of softwash product approvals
Understanding the legalities of softwash product approvals

April 05, 2024 2 Comments

In today's world of "false facts" how can you know which softwash products are legal to use and which are not?

Click the link on this page to find out ...

View full article →

Spring Newsletter 2024
Spring Newsletter 2024

March 29, 2024

Welcome to our Spring quarter newsletter 2024. We catch up about all our softwashing news and discuss issues happening in the trade this season.

Click the link to read more.

View full article →