Loft Condensation (inside OSB board inloft void after conversion) (Ed.)

[fosk]

I had a loft converted a few years ago and on the gable side, the builder insisted on osb board, with mesh and straight cement render, which was painted over with dulux masonry paint.
I've noticed when very cold the inside void of the loft, cold space if you like, the osb board is wet - concerning as i understand it doesnt like to be wet.
The bathroom below I have a upvc ceiling and good extractor fan, the rest of house I have a positive input ventilation system which has eliminated mould and moisture on windows.
In my house the humidity is under control, I also monitor the void in loft space and it is near the same as rest of the house, pic below was setting when osb was wet.
Is it just the fact that there is no thermal barrier on outside of osb causing this? What's the best solution to it?

 

[noseall]

I had a loft converted a few years ago and on the gable side, the builder insisted on osb board, with mesh and straight cement render, which was painted over with dulux masonry paint.
I've noticed when very cold the inside void of the loft, cold space if you like, the osb board is wet - concerning as i understand it doesnt like to be wet.
The bathroom below I have a upvc ceiling and good extractor fan, the rest of house I have a positive input ventilation system which has eliminated mould and moisture on windows.
In my house the humidity is under control, I also monitor the void in loft space and it is near the same as rest of the house, pic below was setting when osb was wet.
Is it just the fact that there is no thermal barrier on outside of osb causing this? What's the best solution to it?

Too much vapour escaping from the house up into the loft. Either vent the loft or improve your ceiling level VCL.

 

[freddiemercurystwin]

Should have used a proper cement render board, cowboy builder.

 

[fosk]

This gable side never sees a bit of sun so I think whatever VC I do, it will still have the problem. It can get moisture from air outside also and condense.

A short term solution could be to drill some vent holes through. Long term I plan to put up a side extension and can address it then properly.

Yes, it seems cowboys in this case. Its not the only problem I've had with the conversion. The bathroom fan wasn't connected to the vent pipe in a cold roof, with inadequate space over the top of the ventilation. Lucky I caught that one. Last week in the storm the Juliet doors had water leaking into 1st floor - new cill required and will need a refit.

Thanks for the responses. Much appreciated.