How to soft wash pebble dash (dry dash, pebbledash) wall render

June 24, 2020 2 Comments

Soft washing pebbledash (dry dash) wall render

In this video (click below) Ben demonstrates how to treat pebble dash ("dry dash") render with Benz Bio Cleanze. This is our usual method and product for treating dry dash/pebble dash render.

Bear in mind that the stains, especially red algae may take a few days to fully fade. This effect will happen more so at cooler times of the year and when the days are shorter.

The render will become progressively cleaner over the coming year because the natural cleaning effect of a Bio Cleanze treatment continues to deep clean over time. And it adds residual protection against re-colonisation.

Can pebble dash be painted?

Yes, but the first question to ask your customer is, “Why would you want to paint the pebble dash?”

The reason to ask is because pebble dash can easily be restored to near new condition with Benz biocidal treatments. And of course, once painted it will need to be re-painted on a regular basis, a process that can easily be put aside. We’ve seen many cases of paint peeling on poorly maintained painted render.

What to do if your customer wants a faster result?

To give your customer the fastest results (if they are about to move home, for example) spray the whole elevation with Lightning Cleanze at 5:1.

Allow it to activate for 30-60 mins before lightly rinsing with garden hose pressure and/or a very wide angle fan nozzle on a pressure washer with the pressure turned down.

After rinsing, give the render some time to dry out. It does not need to be fully dry but should not be saturated. Then gently brush in a second application at 4:1, allowing time for activation before rinsing. You should see some very good results using this method. 

Quick tips:

    1. When applying Lightning Cleanze at 4:1 wear full ppe and take care because of the additional strength.Pebble dash is delicate and must be treated with care because the pebbles can easily be loosened and detached by too vigorous brushing.
    2. The principles of soft washing pebble dash render are similar to soft washing sand & cement render – in that the approach needs to be different to soft washing common through colour render such as KRend and Weber.
    3. For faster results on very heavy colonisation of dry dash render, pre-treat with Bio Cleanze at 20-30:1 and follow up with a treatment of Lightning Cleanze after two months (winter) or one month (summer).
    4. If the render remains seriously discoloured and damp after a soft wash treatment there is a possibility that it could be rising damp. If you think this is the case, which is very rare, check for rising damp and advise your customer to call a specialist.

Quick tip: Bear in mind that pebble/dry dash render can be quite delicate and a gentle approach to treatment is essential. Aggressive brushing and/or high-pressure power washing is strongly contra-indicated.

The most effective method of soft washing dry pebble dash

Dry pebble dash is delicate and can be challenging to clean when the colonisation is particularly severe and it has been poorly maintained for several years.

In this situation the repeated rinsing and brushing required to clean highly colonised pebble dash with Lightning Cleanze alone could dislodge some pebbles from the render.

A Bio Cleanze treatment is a highly effective way of removing organic staining. But by itself it may not give the best results on dry pebble dash that's been very highly colonised. It could take up to a year to show acceptable results and even then some deep black algae stains may remain.

The process we've found to be highly effectively for cleaning dry pebble dash:

  1. Treat with Lightning Cleanze biocide at 4:1.
  2. Immediately follow up by brushing neat Tornado Cleanze into the most severely stained areas. This process requires only one rinsing operation and results in dramatic same day visual results, which customers really appreciate.
  3. We then leave the pebble dash for a few weeks while sun, wind and rain naturally remove much of the debris of dead colonisation. We then treat it with Bio Cleanze biocide at 20-30:1. 

    Bio Cleanze soaks deeply into porous surfaces and into all cracks and crevices, ensure any remaining growths and spores are killed. It continues cleaning over the next months and offers protection against re-colonisation.
  4. Ongoing, offer your customer your "Clean & Maintain" programme to keep their property permanently clean.

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 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

2 Responses

Leo Searle-Hawkins
Leo Searle-Hawkins

March 01, 2021

Hi Brendan,

The pebbles on dry dash render are applied to the surface after the render has been applied. They are kept in place on the surface by the “glue” of the render and not by organic growths, Dry dash contrasts with wet dash, in which pebbles are introduced into the render mix before applying to a wall, leading to a much stronger adhesion. Overly zealous brushing, especially with a hard bristle brush and/or high pressure power washing can easily dislodge the pebbles. This is why we advise a gentle approach to treating this kind of render.

Btw: After treating your neighour’s property with bleach, the organic growths will have been killed, as would appear to be the case for your property (albeit without the long-term protection offered by Bio Cleanze and Perma Cleanze). So if organic growths were actually holding the pebbles onto the wall, the killing of them would similarly have loosened the pebbles.

Brendan Little
Brendan Little

March 01, 2021


I had my white dry dash wall on house treated with Bio Cleanze. It removed the red staining completely but resulted in a big loss of pebbIes. I think the organic growth was actually binding the dash to the render. My neighbour used ordinary undiluted cheap bleach and has no loss of pebbles at all. The bleach just whitened the growth but left it intact to continue to do a good job of keeping the dash on the wall. The bleached growth is not noticeable and looks good. I don’t think biocide is the solution for this kind of finish.



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