On 4 June, 01:42, Matty F wrote:
Perhaps those in the UK don't use or know much about corrugated iron
(=steel) roofing.

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.

However, I have a professionally installed corrugated iron roof. The
installers don't seem to bother blocking off the holes under the lower
edge,

White PE foam filler strips are pretty universal these days.

I'm about to push chicken wire into the gaps and use expanding foam.

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.