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Chapel Conversion - wall design again!


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2 hours ago, RJHumphrey said:


What's the theory behind woodfibre rather than celotex etc, given that its isolated from the main building? Surely thats just more expensive?

What constitutes "extreme" regarding the weather? Rain?


Hello Roger,


I like this about a forum, where people challenge others decisions/ideas, this is not a sarcastic comment, as this makes me revisit my decision process and potentially stops me making a costly mistake. My understanding  is that a breathable wall makeup regulates internal temperstures, assists with the movement of internal moisture through the wall to the vented cavity, which should prevent mold growth.


I have pasted a few snippets from the internet below, I am no weather expert but I have experienced the changeable weather while working on the property, including heavy rain, snow and sunshine all in one day.  no doubt there are stats online for most locations the uk, but the rear of the property is exposed and you can see the driven rain hitting the walls. The chapel is located close to the Sennybridge weather station.


Parts of the UK experienced the coldest night of the season on Tuesday, with temperatures of -9.4C (15F) recorded in the village of Sennybridge, Powys,


The deepest snow recorded was 30 cm (12in) in Sennybridge, near Brecon, while High Wycombe saw 17 cm.


The second named storm of the 2018/19 season brought heavy rain with more than 56.4 mm recorded in Sennybridge, more than half a month's worth of rain.


Agreed. This forum is excellent. A lot of very knowledgeable people. Unlike myself.


Your comments about moisture transmission make sense. If you were attaching it to the walls.


But you are not doing that. Surely, what you are now doing, is to all intents, no different to  traditional cavity construction. Where the inner leaf is usually brick or block. And on newer construction, with celotax nailed to the inner leaf. So no meaningful moisture transmission possible.


Im not convinced you are gaining much with woodfibre other than extra cost? Mind you, ive not really looked at from that angle as its not a route i went down.


Hopefully someone will come along and point out why im wrong?



Edited by Roger440
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7 minutes ago, RJHumphrey said:

What route did you take?


Wood fibre lime plaster straight onto the brickwork


Though i will caveat that by saying, the decision was ultimately driven by the fact that flooding is a risk. So things like woodfibre boards had to be ruled out as "if" it were to get wet, there might be a need for remedial works.


Part of my self imposed remit was "operatin 4". Ie, withing 4 hours of the last drop of water going out the door, id be on the sofa with a cup of tea!


That requires an arrangement that will be unaffected by a couple of hours of water at a depth of no more than 1 inch.


It does, however, mean that heat loss through the exposed wall will always be significant.


Without factoring in flooding, i would have probably use one of the direct onto the wall solutions based on my research.


The challenge with all of this, is there are so many variables, and you probably wont know if you chose the wrong route until a few years later.  But as mentioned earlier, i nearly bought a barn conversion that had been done with a cavity which wasnt without its problems. Though i will never know how bad they were. But it made me wary.

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I need to support the first floor joists, so this is the reason for the stud walls, rightly or wrongly, I wanted to keep the timber off the stone walls, as the battens I removed from the walls when i first stsrted stripping the building weren't in great condtion, rotten and wet, i coulndnt deternine the cause for this, possibly from the leaking roof or moisture from the walls. There are examples of wood fibre wall make up with cavity, see examples below, these are timber clad, but principle is similar. I know this is a more expensive option, but I do think the woodfibre will manage any internal moisture, and reduce the risk of condensation better than a vcl and non breathable insulation route.



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