This digest Part 2 covers the main technical issues and answers the frequently asked questions on the specification, application and performance of AAC blocks in masonry in the light of current regulations and guidance. The topics include: appearance (avoidance and treatment of staining), thin-joint (or thin-bed) AAC masonry, and the physical properties of AAC walls (fire resistance, thermal performance, sound insulation), cutting and fixing, plastering and rendering, repair and remediation are mentioned briefly. It also evaluates the green credentials on the basis of available data on energy and resource usage published by the manufacturing industry. The full list of references, standards, etc for both parts of this Digest is given ONLY in Part 2. Digest 342 is now withdrawn. 12 pages.