Confused here. I've got a conservatory that's coming down once the following has been done. The original kitchen window was opened to create an internal door into the conservatory. I'm wanting this bricked up so I've removed everything. They've left some of the original reveal in so I can see the size it once was making life a bit easier BUT I've noticed something that don't make sense and wana check it'll be OK for s window to go in. It's late 80s cavity 100 brick 100 cavity 100 block The outer skin brick is about 18mm lower than the inside block skin where the original bottom of the reveal was. Is this alright for a window. The original inner block wall also has 2 courses of the outer brick on top of it... I'm confused how this was achieved as I thought 3 bricks with mortar was the height of 1 block?