Plasterboarding new extension

[maccTrier]

Hi I am project managing my new extension - frame is up and we are now ready to start insulating and plasterboarding. Plans specify 100mm thick Kingspan TW55 between the joists then 35mm K18 Kingspan insulated plasterboard. How-To books and telly projects only seem to use 12.5mm plasterboard and I have just costed up doing it in the specified materials and its ridiculously expensive!

Can anyone tell me what is usual? Or do you think my architect gone overboard with the specification ?

Grateful for your opinion.......

 

[freddiemercurystwin]

Roof floor or wall?

Google 'Celotex U Value calculator' and once you've registered (free & instant) you can check it out yourself.

 

[maccTrier]

plans say 12.5mm plasterboard ok for ceiling but k18 on the walls over the TW55 - ouch!

 

[Alastairreid]

If you do it different from the approved plans the bco will want proof that you have achieved the u values.

I'm assuming this is kit built

Anyhoo have you looked at 2nds?

http://www.secondsandco.co.uk/?gclid=CJbF4Z3hwboCFSXItAodIFAA0g

 

[AdamCH]

Separate plasterboard and insulation will work out cheaper than the bonded stuff.

 

[maccTrier]

Thanks for the link and the advice re BC. Yes its a timber frame but built on site. I paid builder to put up the frame and then intend to bring in the trades as i need them but insulate and plasterboard ourselves. Builder thought that 100mm insulation and then 35mm insulated plasterboard was overspecified but its really difficult to work out if using insulation and then 12.5mm plasterboard would meet minimum building standards in Scotland.

i will try the link to the calculator above and have another look at the Domestic Handbook.

 

[Alastairreid]

At a rough guess your detail will achieve approx 0.20W/m²K