Ventilated void needed between rendered screed & stud wa

[Corrado]

I am having my extension built at the moment and the upstairs level is 100mm studwork (exterior):

This has an inner and outer skin of ply and insulation between, with an intended void of 38mm between the outer sheet of ply and the outer cladding (which is 3 coat render on EML and breather paper).

Does the wall need to have the 38mm ventilated gap? It is on the plans, but the builders are adamant that it is not necessary and they have not allowed for this gap!

Can anyone tell me why the gap would need to be there - is it to stop the wood from rotting?

 

[Static]

If you have an architect who drew up the plans, contact him tell him the builders proposal. 99% of the time; if its on the plans its required. The builder has agreed a price to do the job based on those plans, if he wants to miss stuff out ask for a reduction in cost, but get the architect approval first.

 

[Corrado]

yes - just called the architect and he was very annoyed about it - he said that they must have an insulated void. He didnt say why, though, but if he says they need it then, they will have to, I guess!

 

[Static]

Probably sound or U values for heating for building regs. In the end you are paying them to do the job, they might as well do it right. Also if the building control inspector notices the change he may ask for revised plans, calcs etc which would end up costing you.

 

[Deluks]

If you're using timber studwork then I would've thought the airgap is to allow air to circulate, thus avoiding mold/damp/condensation problems as you suspect.

Seriously, builders can be such muppets at times. Some of them never think. They just 'know it all'.