You should also use perimeter strips at the edges where the slab meets external walls (some people recommend the same for internal walls, depending how serious you are about the job). These strips are about 6 inches high and 1 inch thick.
Thanks for all the prompt replies. 500 gauge polythene - good to know.
rmdt, what are the perimeter strips made from ? Do Kingspan do them ?
Jorus, what do you mean by "going to scrape and clean the floor first" -how will you scrape a concrete raft floor ?
birroc.. are you going to slab the internal of the external walls with insulated plasterboard?
No Syd, external walls already plastered. No insulated plasterboard at all, never liked the idea. Went instead for 150mm cavity full fill of ecobeads.
Why do you ask ?
i would incorporate at least a 25mm strip around all the external (and internal!!) rising walls.
I used the xtratherm strips that Sydthebeat mentions. They are 25mm X 150mm X 1400mm and are really handy. It saves cutting strips from full board and have foil on both sides. I put in 75mm xtratherm and will be putting in 75mm screed once the plumber finishes the pipework.
Would you not just build in a set of wallties one block down for FFL.............Birroc,
On the point of starting your cavity wall insulation 225 below FFL.If you are going to do this make sure that you fix this to the inside leaf.Your wall ties will only start at FFL so if you don't fix the insulation below this it will be loose and may lie across the cavity.Any mortar droppings can build up and allow water to seep across your cavity.
Personally I would not put the insulation below FFL for this reason as you will inevitably have a certain amount of mortar dropping and this provides a space for it to accumulate without causing any harm - once it doesnt build up above FFL.
Birroc,
On the point of starting your cavity wall insulation 225 below FFL.If you are going to do this make sure that you fix this to the inside leaf.Your wall ties will only start at FFL so if you don't fix the insulation below this it will be loose and may lie across the cavity.Any mortar droppings can build up and allow water to seep across your cavity.
Personally I would not put the insulation below FFL for this reason as you will inevitably have a certain amount of mortar dropping and this provides a space for it to accumulate without causing any harm - once it doesnt build up above FFL.
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