Window bucks in AAC wall construction

[David Bearss]

I am working on a project where we will be incorporating AAC [autoclaved, aerated concrete] block wall construction. We want to give the masonry dimension for door and window openings. I have been wood frame construction ever since starting to work with ArchiCad and so am unclear how to place windows and doors into a masonry wall so that the rought opening allows for 1-1/2" blocking. I know this product is quite popular in Europe so I am hoping this is an easy solution.

[Thomas Holm]

Here in Sweden we call it simply "lightweight concrete". We use the same masonry tolerances as with brick masonry, so a door frame needs 10-15mm of free space all around to allow for blocking and insulation, that is the wall opening needs to be in total just above one inch bigger than the door frame in both directions.

Edited:
Maybe I should add that it is popular, but not in all circumstances. It contains a lot of water when newly manufactured, so you need to let it dry properly before sealing or putting for example paper-clad gypsum boards (drywall) in direct contact with it. Also, it should not be used below ground since it sucks water - for use in foundtaiton and basement walls, LECA blocks (heat-granulated clay pebbles) are better.