Slate hook length

[rreanor]

I'm re-slating a small roof, and have brazilian slates which apparently are best secured with slate hooks.

I cant figure out what length the hooks need to be, or whether it really matters.

The slates are 500x250, the battens are advised to be 200mm apart (centre to centre) and i need a head lap of 80mm.

What length hook do i need?

 

[DAZB]

Found this for you ....
"The length of the hooks should be no less than 10mm longer than the minimum head lap required."

So 100mmm would be adequate for you.
This also gives a fair guide to installation and suggests a minimum of 5mm longer than headlap.

https://www.google.com/url?sa=t&source=web&rct=j&opi=89978449&url=https://www.barbourproductsearch.info/SSQ-UK-slate-hook-fixing-file016314.pdf&ved=2ahUKEwiB1tDC_biIAxVdTkEAHc2GHRoQFnoECB4QAQ&usg=AOvVaw3aEOAd6TYKCNYIiBjDFb8s