Well, I'm a bit against breaking apart the leca. It's quite sensitive as it is to compression loads. And it's quite difficult to fit the beam with counter tension and without making a giant hole.
Do you already have the beam? Otherwise, I think the angle iron solution is easier to work with.
You can saw out the slots with an angle grinder, drill a couple of holes, and then hammer in the angle iron from inside the room. You won't have to tackle this from the other side.
Alternative 3, you use a flat iron on the wall you can't access, screwed with lightweight concrete screws into the transverse wall.
On this, you weld the angle irons, so you avoid the risk of cracking the tiles on the other side.
It becomes like a post iron then.
Something like this, but much larger and with angle iron.
[link]
Alternative 4
Weld a frame in angle iron, like a picture frame. Then, groove in the leca on each side and mount this frame in the hole, screwing it in with lightweight concrete screws.
After that, it's just about chiseling the iron
What's important is the height of the angle iron, at least 80mm high on the horizontal side, as it will bear the load.
Awesome as always
No, the beam hasn't been purchased, mostly just brainstorming
It's leaning towards, as I understood it, alternative 4, that is, a frame with angles where you hammer in a square with an angle on the outside and bolt it in place
Should it be enough to go in about 20 cm into the leca and 10cm into the angles? Resting area about 15 cm on outer and inner wall?
Next time you need to make a hole in leca...... drill a guide hole so you can fit your angriest saw blade for the reciprocating saw. Then, full speed on the saw and you'll be done in a few minutes. Yes, it smokes like hell.
