Re. the lintel, I was just going by what this video suggested.
Ok, a bit more clarification on the garage. Firstly, it is 100% brick, currently used for storing farm machinery. No dry wall, nothing. Same as our house, everything is built from brick and concrete. I don’t know if dry wall even exists here - never seen it in any house I’ve lived in. It is detached from the house, perhaps 30m away on the driveway next to a field. This is the only photo I can find of it, I’ll take some better shots when I go outside this morning:
https://fbcdn-photos-b-a.akamaihd.net/hphotos-ak-frc3/v/t1.0-0/q88/p180x540/10156078_10151978345326653_52803709109810439_n.jpg?oh=26cb1b5692eabb3e1e047cefb8f683fd&oe=56ABB5E7&gda=1449048369_c210d6d8fa7819d9de3359674bddf6b3
There are no roller doors, instead there are double opening barn style doors at the front made from wood. So makes going in and mucking out the whole thing with a little tractor a piece of cake.
The floor is concrete, but the floor in our main barn is also concrete. We deep litter so the horses wouldn’t be standing on the concrete anyway. Never had an issue with drainage because the bed of straw soaks up any urine and smell. Plenty of fresh straw on top and all is good.
Re ventilation, there is a gap between the roof and the walls that allows for ventilation, plus the horses would never been locked up in there - if they do need to be stabled for whatever reason then they’d come in to the barn. I’m wanting this just to be a place where they can get out of the elements if they want to. Plus it’s about 50 years old so certainly not air tight.
The main thing is putting in a door so they can come in and out. It’s the bashing a hole in the brick wall issue that I am most concerned about at the moment 