The invention includes a method for constructing buildings using non-wood construction products and buildings constructed from such non-wood construction products. The invention further includes a method and apparatus for manufacturing high-performance fiber-reinforced cellular concrete (HPFRCC) products and the use of such products as replacements for conventional wood lumber construction products. The products of the invention have the necessary strength, durability, nailability, and sawability for direct substitution for dimensional wood lumber in wood-frame construction applications. The invention also includes externally reinforced retaining wall systems that include stackable blocks formed of fiber-reinforced cellular concrete.