I'm currently installing external wall insulation (EWI / ETICS) on our 1920s semi-d.

The insulation type mostly EPS, but a few bits of render carrier board, and rockwool (for fire breaks) and thickness varies from wall to wall (e.g. cavity vs. solid).

The windows are all partly or wholly moved out into the plane of the insulation.

The render supplier has supplied window reveal beads (they stocked two types).

Before fitting the beads I was looking at the beads and didn't really think they'd be capable of accommodating much movement. One window is SW facing and pretty large (2.6 m high by 3.4 m wide), and this is in the thickest insulation (280mm).

I found this document from the German Association for Insulation Systems, Plaster and Mortar (VDPM):

https://de.calameo.com/read/00110231894f5dbc36809

"Ausbildung von Details mit Profilen und Fugendichtungsbändern bei Aussenputz und WDVS"

(Formation of details with profiles and joint sealing tapes for external render and ETICS)

Google Translate does a reasonable job on it, and there's an extract in English on this supplier's site as part of this catalogue (page 12):

https://www.ejot.de/medias/sys_master/Catalogues%20ETICS/cat-etics/h73/h0d/9230512685086/EJOT-cat-profile-2022-03-25-EN.pdf

... this says that we need high movement ("Class A") window reveal beads for most locations.

From looking at other manufacturers' catalogues, it looks like the beads we currently have here are probably "Class C" (with not much movement, and definitely not up to spec for the big window).

Any tips on any UK suppliers which might stock high movement "Class A" beads?

Hmmm - I've always regarded the pathetic 5mm wide strip of self adhesive feeble-foam as just something to hold the bead in place until 'locked' into the render - then rake out as much as poss of the adhesive strip and gun in a good wodge of 8mm deep x 3mm thick of top quality sealant. That should give considerable shear movement - or as the guy says in https://www.youtube.com/watch?v=L2jOIKSga9s, does that sealant really have to be renewed 'every couple of years?' I wonder how long the APU's flexing membrane would last, exposed as it is to UV? The APU has a much wider strip of self-adhesive, but everyting depends on that lasting forever. Still if dear old Chris Brookman of Back to Earth https://www.youtube.com/watch?v=_MEGziU967Y stocks and recommends APU, prob how it will be.

Posted By: fostertom8mm deep x 3mm thick of top quality sealant

Thanks both for ideas.

I was under the impression that the thing to do for good movement from sealant joins (without pull-away) a sort "diablo" or "hour glass" cross-section - I think that's what you're describing (not sure which way around the "deep" and "thick" are in that sentence). i.e. relatively large bond area to both surfaces, but skinny (and unbonded) in the middle to allow movement without pull-away. e.g. the type of thing you get by using a PE foam "backing rod" with sealant over the top of it.

That's my fall-back, but would prefer to try and get hold of some of these uber-beads, rather than trying to improvise after the render is done.

Assuming I can get hold of something like the two high movement beads mentioned above, I was thinking of removing the sticky-back-plastic tape from them, and using a facade-specific MS-Polymer or something like Stelmax 1961 to fuse the PVC bead directly to the PVC window and door frames.