Perhaps those in the UK don't use or know much about corrugated iron
(=steel) roofing. It's widely used here in NZ. It's very strong and
and cheap and holds the house together in an earthquake or hurricane.
You can walk all over it without falling through.
However, I have a professionally installed corrugated iron roof. The
installers don't seem to bother blocking off the holes under the lower
edge, so the wind can whistle through, and rats and mice can get in.
They do use building paper, but that's no problem for the rats.
What are they supposed to do instead to block the gaps?
I'm about to push chicken wire into the gaps and use expanding foam.
We do have the occasional bit of corrugated iron around here - I've just put
a tin roof on my shed (plastic covered and a different profile) and
corrugated iron is widely used in agricultural buildings.
As is asbestos sheeting, but that's another story.
I would normally expect some ventilation under the roof - assuming that
there is insulation and a ceiling beneath - otherwise you get condensation.
However I would also expect it to be bird and insect proof.
Chicken wire and foam sounds as though it would work.
Haven't seen new traditional "corrrugated iron" in years. It's not
used much at retail or DIY level, farms use large-section trapezoidal
box with a factory plastic coating, retail parks and cheap warehouses
use the small-section trapezoidal section that's put through a crimper
to curve it rather than rolling it.
White PE foam filler strips are pretty universal these days.
Use paper, not wire. Unless you're rat-proofing too, in which case,
use both. Foam's not cheap when you're using it in this quantity and
it's worth limiting the squirt-through.
My several roofs are mostly large or small corrugation asbestos and
old enough that they were sealed with mortar or nothing, both of which
have since fallen out. I've a lot of squirty holding things together
now. My big tin shed ('80s new build) had foam fillers from new.
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