Producers of autoclaved aerated concrete (AAC) offer not only blocks and panels for constructing walls, but also AAC floor planks. This product is popular for building floor and roof decks atop AAC walls, creating an integrated structure with a consistent set of materials. The advantages of AAC extend throughout the shell.
To accommodate a deck above, the walls are constructed with vertical rebar of a length to extend several inches beyond the top of the wall. These bars are hooked on the end so they can lap a horizontal line of bars above. The horizontal bar is wired in position on the hooks.
AAC floor planks are typically 2 feet wide and cut to length in the factory. Onsite, the planks are lifted into position with a crane, extending from the front to the back walls. They must have a minimum of 2½ inches of bearing on each wall, although more may be required by floor loads or other factors. Floor planks are manufactured with integral steel reinforcing, have no camber, and usually require no bracing.
The planks have a notch along their upper edges so that when two of them are placed side by side they form a beam pocket between them that runs the span of the floor. This produces one pocket every 2 feet on center.
An additional line of rebar goes into each beam pocket. This bar extends out of the end of the pocket and is bent on the end. The bend hooks around the horizontal rebar above the wall, creating a structural connection between the wall and the deck, even if the beam pockets and the vertical bars extending from the wall do not line up.
Along the top of the wall on the outside, a rim form of AAC material is set in place. This form is typically sized so that its top edge matches the top surface of the planks. In unusual cases a concrete topping will be applied over the planks to increase floor strength and in those cases the top of the rim form has to be higher than the planks' top surface by the depth of the topping. The rim form can be held in place temporarily with 2x lumber or strips of plywood attached to the outside of the wall along its top edge. The brace extends above the top of the wall to back up the form. The rim form stays in position permanently to give the exterior a consistent layer of insulation and surface material.
An elevated flatwork crew places concrete in the beam pockets. Concrete also goes in the space between the rim forms and the planks, which creates a bond beam on top of the wall and structurally ties wall and floor together
The planks, even without a topping, are usually satisfactory for application of conventional floor coverings. In some cases a thin layer of gypcrete may be applied for precise leveling.
—Pieter VanderWerf and Ivan Panushev work for Building Works, Inc., a consulting firm that helps companies introduce new construction products. They may be contacted at www.buildingworks.com.