How to extend handrail post for pergola

Hi all,

I’ve recently built a deck where the 135x135mm Cyprus posts go all the way from the stump holes up to support the subfloor and through to create the handrail.

However I now need to build a pergola over the deck, and rather than pulling down the handrail and fixing the pergola posts to the subfloor frame and having to re do the handrail, I was hoping to leave the handrail in place and try and splice the pergola post on top of the existing handrail posts.

I’m wondering if it will be structural enough. I’m thinking of either doing a half lap joint to connect the two posts, or otherwise checking a big steel rod into the centre of both posts, and then putting some sort of bracket or sleeve connecting the two posts.

As for how the frame will connect to the existing house, I’m planning on using roof extenda’s through the tiled roof of the house.

Does anyone have any advice on this?

Cheers!