You can get a rough finish with sprayed on monocouche see attached:-

I'm guessing, but for a good job you may need to smooth render the pebbledash to true it up first.

ttps://www.uk.weber/blog/how-guides/how-achieve-roughcast-texture-finish

When I am putting EWI over an uneven surface I put a bead of adhesive top and bottom of each board with 3 or 4 dollops in the middle. This will stop any air flow at the back of the EWI

Some contractors recommend rendering the wall to a smooth flat finish but IMO that is unnecessary and 'job creation'.

Whether to use mechanical fixing or not depends upon the wall and the location. E.g. I have a basalt stone wall that it is impossible to get mechanical fixing in. The wall is fairly exposed and faces north. The EWI has been on about 12 years without mechanical fixings and no problems.

On top of the EPS there should be a 5mm coat of adhesive with glass mesh bedded in. This is important to stop cracks appearing in the final finish.

The thin film render is the final coat to add a decorative colour and better weatherproofing. This is about 3mm thick and the thickness is governed by the size of the aggregate. Over here you can get 1.5 mm or 2 mm aggregate depending upon what thickness you want. (I think thicker is seen as a better quality job but obviously more expensive as more render is used).

Over here the colour you want is mixed in the builders merchant with machine measured colouring agents so there is no waiting for your particular colour to be ordered. I have never had colour shading issues with this system.

Posted By: bhommelsWetherby do a spar dash receiver finish: https://www.wbs-ltd.co.uk/systems-solutions/system-finishes/dry-dash-aggregate/

The site says it is waterproof - it doesn't say it is breathable (that I could see)

Ive installed EWI of rough cast.
We chipped off any larger protruding bits and hard brushed it to get rid of any loose bits.
We then fixed boards using expanding foam and 2 mechanical fixings.
Foam fixed boards and stopped air movement , bead of foam round edge and two line creating thirds
Then did the standard mesh coat render over top .
10 years and its still looking good. house is just round the corner from me.

My neighbours council, they EWI terraces along my road with pebbledash , looks good , use two different undercoat colours and a horizantal bead at storey height which broke it up a bit.
its wearing much better than the finer grits finish on my place and the flats near by.

'Harling' is used round here as a catch-all term to mean all the above techniques (guess every region has different building language!). Most usually, sharp dry 8-10mm chippings of local stone are thrown (harled = hurled) against wet cement render. Then firmed in with a trowel, pushed in deep enough so the colour of the chippings is still visible but they don't fall off (even when wiggled!).

The colour of the building comes from the local stone chippings, which are the right colour to match local stone buildings, and often have some quartz in them which 'sparkles' a little in the sun. After a few years the raw stone chippings get mellowed by lichen (?) growing between them. That's the look that is wanted here.

Thanks everyone for the links!

Still looking for an EWI 'system' that allows this IE a thick enough render (10mm?) to receive the chippings. Is it as simple as just using the usual cement render, onto mechanically fixed mesh over the insulation boards?

Edit: looked again at Bhommel's link https://www.wbs-ltd.co.uk/systems-solutions/system-finishes/dry-dash-aggregate/ which looks ideal, mentions use over EWI. Thanks!

I mean like Tony mentioned - the mesh (he mentioned metal plaster lath) is mech fixed onto/through the insulation, then the heavy render+chips are applied to the mesh. The mech fixings support the weight of the thick render+chippings.

<blockquote><cite>Posted By: tony</cite>No need to chip off existing render, ensure air can’t flow round and in and out of any voids.

We have affixes expanded metal lathing over the insulation using insulation fixings then three coat render with finish applied to the topcoat. Might need engineering detail for it

</blockquote>
i did the above on my external insulation using K rend and black and white marble chips its done 15 years now and its still fine i just clean it once a year with diluted bleach from a nap sack sprayer to keep it white

I have an " aggregate dash" finish on my EWI no metal reinforcement simply the reinforcement scrim as shown in the product video

The finish blends in well not found any need for maintenance in approx 10 years.

The chips, I chose still have very sharp edges and still gradually reduce in number but without detracting from the appearance


see 7 min video

https://www.youtube.com/watch?v=4zfo-vcXLJE


I did buy shares in the company (which I still hold) in an unsuccessful attempt to get remedial work done without actually going to court

Company wise a disappointing investment but I still think it to be a first class product but as ever ; it relies on the contractor actually doing the work correctly.

Make no mistake .


My investment in EWI was very well worthwhile and I would and do recommend it to everyone .

It has saved unknown tonnes of Co2 release .

As far as I could see, at that time , the BBA were simply publishers of companies literature,( for a fee. )

and my so called insurance was worthless IMO.

One would like to think times have changed but some how I doubt it

<blockquote><cite>Posted By: Peter_in_Hungary</cite><blockquote><cite>Posted By: dathi</cite>i just clean it once a year with diluted bleach from a nap sack sprayer to keep it white</blockquote>
What dilution do you use ?</blockquote>
i just use toilet bleach out of aldi/lidl mixed 50/50 with water i just spray it on and leave it i don't wash it off