Nice work, Tom! It's looking pretty good up there.
I bet trying to maneuver those monsters in that tight space was... ummm ... "fun"!
With the holes in the ceiling I decided to remove the timber altogether, then I plan to fit the sleeves, then shutter around them and pour concrete for mass to make the holes exactly right. As I’m writing this I have realised that this will couple the sleeve to the ceiling which we don’t want
Right! We definitely don't want any solid mechanical connections there!
...so I’ll actually need to separate them when shuttering then probably backer rod and caulk the life out of it? Stuart?
Sounds like a good plan. I'm wondering if there's a way to do that filling in stages, starting from the top and working down, so you can get plenty of depth to the caulk and backer rod? You'll need a total thickness for the caulk of about 3 cm (more is better!), but you can't do that all in one go: it needs to be built up in layers, or it won't cure properly: let each layer cure before adding the next.
I'll see if I can think of any other way of doing this...
Also, when you pour that new cement in, do make sure you use some concrete bonding agent! Otherwise the new won't stick to the old. There's several different ways of doing that, but likely you'll want to paint some bonding agent onto the old concrete surfaces, and/or mix in some other agent with the new concrete, so it can bind tightly to the old.
- Stuart -