I’m currently on the home stretch of specifying a small EWI project onto solid walled brick and block. 90mm is the absolute max we can fit under the eaves so I’d rather this didn’t turn a debate about how much insulation I should have.

We are trying to replicate the cant brick cills of the rest of the house over the EWI in bespoke brick slips to keep some architectural continuity between the main house and EWI region.

My original plan (see image) was to add slips to the phenolic with brick slip Adhesive and point with brick slip pointing mortar. However the EWI system manufacturer recons this will void my warrantee as there could be stress on the insulation and their guidance states that cills must exert no stress on the EWI.

My revised plan was to construct a structural cills from left over foamglass perinsul blocks and apply the slips to the rough glass edge after rasping it into the right shape (see image). However Corning state that nothing will stick to foamglass as its not permeable.

Any suggestions on simple routes forward? I’ve seen details like this on EWI before but the only cast iron approach anyone can suggest is to have whole cant bricks bridging the EWI.

Posted By: jms452My revised plan was to construct a structural cills from left over foamglass perinsul blocks and apply the slips to the rough glass edge after rasping it into the right shape (see image). However Corning state that nothing will stick to foamglass as its not permeable.

You might have better luck with Marmox Thermoblocks instead of foamglass. I've no idea whether you can carve them but I'm pretty sure you can glue them.
http://www.marmox.co.uk/products/thermoblock

It might also be worth speaking to an adhesive manufacturer rather than the foamglass manufacturer; they might take it as a personal challenge to find a suitable glue!

Thanks tom and dgh.

Tom
The stone cills do indeed look nice but won't match the rest of the house - maybe I could use a renderbrick system and apply the gloss paint to it and the rest of the cills so they all match but I'm not quite ready to give up on my brick cills yet.

dgh
Marmox has a conductivity of about 0.07 but the minimum order and delivery will be pricy - I could swap foamglas for something easy like celcon standard at 0.15 or celcon solar at 0.11 which I can buy individually for a couple of £. That is probably my best option to date and I could probably get the cill to a u value ot 0.5.

go on...

You reckon the glassfibre mesh reinf acrylic render top surface will crack up eventually and let water into the EPS? I don't mind a Al flashing over the top of it - cos will bend them up to order and powder coat quite cheap, even make a tray of it turning up back and ends of the window's cill. Just adds cost and complication.

eh?

dON'T KNOW - JUST AT THE BEGINNING OF GETTING TO KNOW ewi. (DRAT CAPS!)

This may sound daft, but I've made lots of composite aircraft parts using EPS foam as the core and epoxy resin and glass cloth as the structural skin. The technique is easy to learn, doesn't smell much (unlike polyester resisn, which attacks EPS, epoxy is almost odourless) and gives great strength and impact resistance. It needs a UV resistant coating, but I'd have thought that it'd be a technique that might lend itself well to details like cills etc.

Can't you get L-shape corners of stik-a-brik?

No, and I haven't used slips at all yet - a pleasure to come!

Find some competent plasterers, bypass the old fashioned EWI supply-and-fit cos or even the supply-only franchise holders. Like underfloor heating, all this stuff is on the verge of becoming commodity items, free of mystique.

photos