Foundation Walls

Foundation Walls (Stem Walls) may be specified by the architect or structural engineer to either be:
• Concrete – poured into wood forms which are eventually stripped away
• Concrete block – solid grouted
• Omni Block – insulated in the exterior cells and solid grouted in the interior cells

Insulated Stem The exterior Omni Block cells are insulated with the Long Insert. This insulation protects the slab from heat gain or loss.

Vertical Rebar Vertical rebar placement is critical. The initial proper frequency, spacing and location within the wall facilitates how quickly the walls can be erected. The photo below depicts an Omni Block stem. All vertical rebar is contained within the Omni Block grout cells and will be in the proper location for the subsequent courses. There appears to be additional rebar that may have been required from the footings to the the stem, but now can be eliminated by cutting the rebar immediately above the stem. The vertical rebar must extend a minimum of 40 bar diameters (5/8″ rebar times 40 equals 25 inches) above the top of the stem wall.

Electrical and Plumbing EmbedsAnother advantage of an Omni Block stem is that electrical conduit and waste vents can be installed prior to the stem being grouted. This allows for these items to be ran under the slab.

Poured-In-Place and Concrete Block StemsThe mason can bend rebar to “hit” the proper Omni Stretcher Block grout cells; or use a Corner Block the first course due to their larger cells. But if the rebar is not close to the proper location, the mason must drill into the concrete stem wall a minimum of 8″ add an epoxy into the hole and then place an adequate length of rebar into the epoxied hole.

This can be a laborious, time-consuming , and costly process, so extra attention by the concrete sub-contractor when placing the vertical rebar is of great importance. Omni Block regularly supplies a ‘vertical rebar shop drawing’ in order to facilitate the accurate placement of the vertical rebar.