Corroded lead flashing from condensation

[John D v2.0]

Hi all hope you're well

I've just taken the lead off our flat to pitched roof drip and it's a right state underneath after 5 years.
This is because the flat roof deck is impermeable so any condensation will form on the cold lead as it goes underneath it.
It's a cold roof above the loft storage.

What is the best practice for preventing this when the new lead goes down?

I've read about chalk emulsion but it doesn't look like something readily available.
Thanks in advance.

 

[freddiemercurystwin]

The lead should be vented I think, believe it or not, there's a thread on here with something about it, I'll see if I can find it. Hardmetal or justlead were your men for that but I've not seen them on here for years.

Edit https://www.diynot.com/diy/threads/lead-flat-roof-ventilation-required.197092/

 

[datarebal]

penny gapped board or building paper. not onto ply or osb.

venting is good too.