I am going to replace an old barn roof and I'm a bit unsure about using condensation protection.
Today there are:
boards on the inside of the rafters.
Then about 10cm of insulation on the boards
Rough beams about CC-100 on the rafters
Eternit sheets bolted to the beams.
I initially thought of building a standard roof with tongue and groove, felt, and battens, but someone suggested just laying condensation plastic or similar under the metal sheets and skipping both the tongue and groove and felt. Apparently, it's standard practice on new roofs for agricultural buildings, and it obviously saves a lot of work and even some money. However, I have never used this technique and haven't found a clear description of it online, like I did when I replaced a regular roof last year. I have at least received "reinforced foil" which is supposed to be made for this purpose, and what I'm mainly wondering is:
Should I lay the foil on top of the rafters and then beam up for the metal sheets, or should I lay the foil on top of the beams directly under the metal sheets?
How do you handle the eave? Do I fold the foil around at the bottom, or do I let it hang the same length as the metal sheets?
Should I nail freely, or be careful to only fasten where there is an overlap?
Will the foil become "wet" from the metal sheet's condensation and lie like a damp rag against the wood underneath? Or is it so dense that there is a risk of condensation forming from the animals' moisture underneath instead? Both alternatives feel wrong...
Today there are:
boards on the inside of the rafters.
Then about 10cm of insulation on the boards
Rough beams about CC-100 on the rafters
Eternit sheets bolted to the beams.
I initially thought of building a standard roof with tongue and groove, felt, and battens, but someone suggested just laying condensation plastic or similar under the metal sheets and skipping both the tongue and groove and felt. Apparently, it's standard practice on new roofs for agricultural buildings, and it obviously saves a lot of work and even some money. However, I have never used this technique and haven't found a clear description of it online, like I did when I replaced a regular roof last year. I have at least received "reinforced foil" which is supposed to be made for this purpose, and what I'm mainly wondering is:
Should I lay the foil on top of the rafters and then beam up for the metal sheets, or should I lay the foil on top of the beams directly under the metal sheets?
How do you handle the eave? Do I fold the foil around at the bottom, or do I let it hang the same length as the metal sheets?
Should I nail freely, or be careful to only fasten where there is an overlap?
Will the foil become "wet" from the metal sheet's condensation and lie like a damp rag against the wood underneath? Or is it so dense that there is a risk of condensation forming from the animals' moisture underneath instead? Both alternatives feel wrong...
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