Double Layer Insulation with infill

[ricardo100671]

We have a 193 Bungalow, plannig to attach 2 layers of 50mm K5. Problem is Upper half of walls, is pebble dash, protruding by ~25mm and therefore would like inlfill lower half, as cheaply as possibe. Thinking to use 25mm XPS all the way to the ground, then over the lot with the K5. So, effectively, would have three layers on lower half (XPS+K5+K5) and two upper half (K5+K5). Would glue first layers with EWI 225 Premium, possibly full face coverage for the XPS and D&D for the K5. Then mechanically fix next layers with centered single fixing per board, followed by top layer with 5 fixings per board.

Folks at EWI store told me I could not do 3 layers i.e. XPS+K5+K5, something about the K5 faces being to smooth, or something, allowing movement between layers, and advised to build up lower half with their mortar infiil, which would require 153 bags costing 1600 ex VAT and labour !

If movement between layer is really an issues, could I not just also add thin layer of adhesive between layer?

Thanks in advance for any aevice 

 

[nod]

The EWI goes up in increments of 10 mil Ive done plenty like yours and used two different thicknesses 

in your case 20 mil thicker for the bottom