kingspan confused!

[dang]

hello all, I am confused as it states different ways all over the net on how to use kingspan, I am building a consevatory and putting the insulation straight on top of the concrete slab, now it states on the kingspan site that an extra layer of dpm on top of the concrete but in another part it says the kingspan can go straight on top? I already have a dpm under the concrete and a local builder says another dpm on the top of it will make the slab sweat.

 

[JoeMar]

hi

the second dpm goes on top of the insulation to protect it from the water in the screed.

 

[dang]

what would the method be with chipboard instead of screed?

 

[jeds]

It's common practice to specify a membrane over the insulation to act as a vapour barrier - this prevents vapour reaching the underside of the insulation (the cold side) where is would condense. If in doubt you should put one above AND below but where you allready have an intact membrane within an existing structure then just a vapour barrier above is sufficient.

 

[dang]

so dpm-kingspan-vapour barrier what ever floor i want be screed or boards. I always thought that the vapour from the drying concrete would attack the kingspan or so i was told by the local builders merchant

 

[ColJack]

if you put it silver foil side up and tape all of the joints with silver foil tape, wouldn't that suffice?

 

[ajrobb]

if you put it silver foil side up and tape all of the joints with silver foil tape, wouldn't that suffice?

I think that would be fine under tongued and grooved chipboard. Concrete in a screed attacks the aluminium foil - hence the requirement for polythene sheet.

 

[dang]

if you put it silver foil side up and tape all of the joints with silver foil tape, wouldn't that suffice?

I think that would be fine under tongued and grooved chipboard. Concrete in a screed attacks the aluminium foil - hence the requirement for polythene sheet.

I heard that about it attacking the board in some way this is why I wanted to ask about it going on top on the concrete floor with nothing between them. Dont want it to become a problem a few years from now.

 

[freddiemercurystwin]

Its also to stop the screed seeping into the gaps. You can achieve the same by taping the joints. If a membrane is used you can use a 125micron polythene sheet.