How to soft wash pebble dash (dry dash) 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 (aka "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.

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 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.

Important: 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.

Benz soft washing how-to videos cover every aspect of soft washing. We show you how to soft wash domestic and commercial roofs, paths and drives, tarmac, concrete, walls, wall render (including KRend, Monocouche, Weber), wet pour safety surfaces, tennis courts, car parks, wood decking, fences, sheds and more ...


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Click here to visit our softwashing how-to YouTube channel

Our sincere wishes for a good life and a profitable business,

Ben, Leo & Fiona


Click here to explore the full range of Benz popular softwash cleaning products

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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