Internal Wall Insualtion

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I am installing internal wall insulation into a 1900 solid stone wall cottage. My Building warrent states the following.

New 25mm thick cavity between the natural stone wall and new insulation to be formed using 25x47mm timber battens at 600mm centres. 100mm Kingspan Kooltherm K12 to be mechanically fixed to new timber battens. 1 Layer of Glidevale VC Foil Ultra (combined vapour and air barrier) fixed to wall, with all reveals/laps taped up in accordance with the manufacturer’s printed instructions.
20mm service void to be formed between new insulation and plasterboard finish for new services – no services to penetrate the new insulation. 12.5mm plasterboard

As old walls are very uneven I would like to do the following.

100x45 C16 fixed at floor and ceiling joist, 25mm air gap behind this to the uneven stone.

100mm Kingspan tight fit between new timbers at 600 centres.

VCL

24x45 Batten – To create service area

12.5mm Plasterboard.

Can anyone see an issue with this?

Cheers
 
Last edited:
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Whenever I've noted a wall specification on a drawing in this situation I've always fixed studs between floor and ceiling joists to cope with the existing wall irregularities so a nominal 25mm gap behind and that avoids any fixings into the existing wall too. Alternatively you could use 125 studs and ditch the battens and chop a channel out of the front of the studs as appropriate for any services. BC have been happy with FB plasterboard too instead of a separate VB.
 
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The main issue is that you're not doing what you said you'd do in your building warrant application.
Are you planning to submit an ammendment, or just do something different and hope they don't notice?
 
The main issue is that you're not doing what you said you'd do in your building warrant application.
Are you planning to submit an ammendment, or just do something different and hope they don't notice?
The main issue is that it complies not that it's different to the plans. :rolleyes:
 
Thanks all.
I have do to some amendments to the warrant anyway so would do this too. Just waiting to make sure my build up is OK.
I guess I would need to use treated timber in this as there is a possible chance of moisture?
 
Well that rather depends on the existing walls, given that your original spec has no waterproofing applied to the existing wall do we take it that the external wall has never leaked or been damp etc? In which case why should there be any moisture present? And if there is a danger of penetrating moisture/damp from the outside then treating the existing wall shoud be carried out.
 
Great, I have stripped the place back to the stone, and see some signs of moisture as it is solid sandstone looking online this is normal, etc.
 
I wouldn't say its normal for an external wall to be damp on the inside. How much damp? Is this historic damp or maybe condensation from being unoccupied for years, a full renovation that you've not lived in before or what?
 
It would just be the place has been empty for over 1 year, it has no damp course at all, built 1900 so guess it happens, no heating etc all that time. I have not lived in, living in a caravan while I renovate it.
 
When it rains, you can see a slight colour change at some points, mainly near the grown level. I have taken up all the floors, as there is just dirt under.
 
Sounds like some tanking internally is in order ....... have you budgeted for that?

What's going on on the outer face of the wall, rendered or pointed or what?
 
I have not, no one mentioned it, last time that was talked about I was informed that sandstone must not be sealed as it needs to "breath" hence the 25mm air gap.
 

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