Concrete masonry units.

A coated concrete masonry unit parapet wall with stainless steel coping, modified bitumen base flashing, and surface-mounted metal counter-flashing.

Useful Links:

1. General: A very good general article on masonry wall systems is available on this page at the Whole Building Design Guide website, which is maintained by the National Institute of Building Sciences.

2. General: "Wall Systems" is another useful general article at the Whole Building Design Guide site.

3. General: "Concrete Block: Characteristics, Uses And Problems". Very short and basic. Available on the website of the US General Services Administration.

4. Maintenance: See the "Unit Masonry" section on this page of the GSA website for several technical bulletins regarding cleaning and maintenance of masonry walls.

5. Technical: Expansion Joints: "Accommodating Expansion of Brickwork" is a detailed illustrated article available on the website of the Brick Industry Association. Includes information about other types of masonry. Very useful.

6. Technical: The International Masonry Institute has a great selection of masonry construction details available, as well as several other masonry information resources. 

7. Waterproofing: "Durable Waterproofing for Concrete Masonry Walls: Redundancy Required" is a good introductory article. Available at the website of the Construction Specifier - the Official Magazine of CSI, which is produced by the Construction Specifications Institute.