Best way to sure up / reinforce this purlin?

[djangofango]

Found a whole bunch of issues in our loft that I need to fix.

One side purlin looks like this:

Obviously done really badly.

Notes:
- purlin is angled into the wall.
- one side has 25mm support on the wall, the back has about 65mm

So obviously not the recommended 150mm into the wall and also not cemented in.
The house is a small terrace but is on a very busy road with lots of truck traffic shaking the ground.

Best way to structurally fix asap (I am losing sleep)?
Surveyor wasn't able to get proper access to loft space - you live you learn the hard way.

Options I am considering:
- support purlin with steel bracket chemically fixed into the wall.
- support purlin with strut fixed to the party wall and also attached to/sitting on a joist below.
- cement in the space to fill the void around the purlin end.

Thoughts?

Tips?

ie. best cement mix? size of timber?

note: I have done lots of finish carpentry but not roofs before.

 

[Koolpc]

Its prob been like that for over a 100 years!! It aint going anywhere!

 

[djangofango]

Thanks Sarah,
One other consideration I forgot to mention is that the mortar around the purlin and (crumbling underneath) is lime mortar. Should I fill in with the same?
I have other posts to come - there is an unsupported chimney breast up there that also needs sorting... worryingly that is also lime mortar.

 

[Harry Bloomfield]

I would track down 2 foot long length of steel angle, as wide as purlin. I would then add a temporary, bracket fixed on that wall, and jack the purlin up just enough, to enable the top brick to be removed - remove the top brick and cut it to allow for the extra depth, and mortar back in place. Add some 10mm bolts, bolting the angle to the purlin, lower back down after letting the mortar set for seven days, and add additional mortar.

 

[Scally-Ho]

Thanks Sarah,
One other consideration I forgot to mention is that the mortar around the purlin and (crumbling underneath) is lime mortar. Should I fill in with the same?
I have other posts to come - there is an unsupported chimney breast up there that also needs sorting... worryingly that is also lime mortar.

Photos please.