Necessary to plasterboard the walls?

[psarinuk]

Hi all,

I am nearly completing on a 3 meter single storey rear extension in a terrace house, the work has been on building notice.

The external wall is brick with 75mm cavity of dritherm32 and 100mm thermal block work on the inside, all looking nice and straight.

My question is do I really need to put plasterboard on the walls and then do a skim finish OR can I have the blocks rendered and then skimmed on top?

I hope the latter option is allowed as it would save us more space and money. I was going to ring the surveyor but thought I will ask on here first for info

Thank you all in advance

 

[tony1851]

The U-values quoted by most insulation-product manufacturers usually assume a plasterboard and skim finish, so rendering direct on the blockwork will presumably give a slightly higher (and hence worse) U-value. The difference, though, will only be marginal.
If the inspector is not happy with this, offer to put some extra insulation in the ceiling, for example (ie a trade-off).

 

[noseall]

I would say that a two coat LWR (light-weight render) i.e. carlite browning etc, with skim finish will be ok.

 

[noseall]

I would say that a two coat LWR (light-weight render) i.e. carlite browning etc, with skim finish will be ok.

 

[psarinuk]

Thanks for your replies folks.

Can someone also advise with regards to loft insulation for my single storey rear extension??

The size of roof from inside is 6 meters by 3 meters. The joists are 150mm by 50mm at a gap of 400mm.

I've 2 left over boards (1200 by 2400mm) of 100mm Quinntherm floor insulation. Can I use them for loft insulation? Do I need more than 100mm overall for the roof?

Can someone advise on the insulation board height and material/ cost please?

Thanks once again.

 

[psarinuk]

Hi again,

I am doing pipe work for the new radiators that are going on these walls, once they are plastered. Apart from the standard gap of 40mm for the valves from the wall, how much extra gap should I leave for the coats of render and skim finish?

Please note while advising that the render is going on thermal blocks, with skim finish on top.

Thanks in advance..