EWI spec confusion just before start of installation

[Linto]

Thank to an initial miscommunication on my part (which I thought had been sorted)  when the builder has come to install the EWI we seem to have some different ideas.

By my reading of the BBA certificate the boards should be fixed mechanically and with a suitable mortar. It's a bit vague but the image on the spec seems to show both.

The builder is currently just planning on using mechanical fixings.

I'd be ok with this but would the ewi perform better with both or should I just say ok but ask him to foam around the external edges to ensure air can't get behind it?

If both is best I'll take the hit in increased costs as the issue seems to stem from the initial problem. 

What do you all think?

 

[SimonD]

The proper way is to have adhesive mortar and mechanical fixings. The mortar obviously has a role as an adhesive but it also evens out the substrate. The mortar also prevents convective air movement behind the ewi which can have a significant impact on performance. Depending on the brand the adhesive can be applied in a continuous cover, or as thicker beads around the back perimeter of the boards with some dollops in the centre.

 

Question is whether if the builder didn't know this, is he up to the job? EWI detailing is important, round all the penetrations and at eaves and dpc level. Has this been designed, discussed and agreed? Do you have drawings or anything confirming the detailing?

 

[Redbeard]

Agree with @SimonD. I would definitely go for adhesive *and* mech fixings. Make sure the adhesive is either full coverage or full perimeter bead and 'dobs'. I had a job done for a client and had had the full spec and method statement saying adhesive and mech fixings, only to find the fitters half-way up the wall, 'dry' (mech fixings only).

[Linto]

Thing is the builder is going off the k rend spec as supplied by k rends qs for their system e. This is the thing that's getting to me, k rend haven't specified it. 

Looking at their BBA certificate it's not that clear either. 

Will just get him to use adhesive.

Question is, which one? A render based one or an expanding foam type?