Attic Rafter Ties Removal

[Páid]

I'm hoping to make some space available in my attic. I don't want to do a full attic conversion as I really only need storage space.

The house is a Semi-D with a hipped roof. There are three rafter ties, two of which restrict a person's movement in the attic as they are at waist level. The third is along the party wall so it's out of the way. I intend to get a qualified roofer to remove the two rafter ties and replace them with something else. I have two questions that I need clarity on;

1. What are the alternative to rafter ties? I want to educate myself in advance of the roofer inspecting the roof so I know what's involved.
2. What certification do I need once the job is done? To satisfy house insurance, building code, etc.

 

[Baby boomer]

I believe the theory is that rafter ties are meant to prevent the rafters (and the roof!) separating at the ridge due to updrafts from wind. Seems an unlikely occurrence but you never know!

Might be possible to replace timber ties with steel members about a foot or so below ridge level. That would give you better headroom. But I'd get a surveyor or engineer to check it out first.