Asked & Answered: How Does Rebar Interact With BuildBlock Webs?
Reinforcing ICF Walls
The plastic ties (or webs) in BuildBlock ICFs hold the two foam panels together and are embedded in the foam. This provides furring strips as well as options to place rebar in the proper position in the wall. Steel rebar reinforcement is required and the plastic webs help to hold it in place. This rebar gives concrete the additional strength needed to resist different types of pressures. It’s the combination of reinforcement and concrete that makes a BuildBlock wall so strong.
Since rebar can’t be made to be continuous for every project, lengths of rebar are cut and overlapped to mimic a continuous bar. This is done in all concrete construction. There are two types of laps in concrete construction, contact, and non-contact laps.
A contact lap means that the two connecting pieces of rebar touch. Typically in poured concrete, this means that the rebar is tied together to hold it in the proper place before and during the pour. There is no additional strength gained by the rebar tie, it simply keeps it in place. The strength comes from the steel being continuous and this continual line of steel reinforcement is easily and efficiently accomplished with BuildBlock’s web fingers. In BuildBlock ICFs, the webs are designed with locking rebar holders. Even in our smallest blocks, two #5 rebar can be held, lapped correctly, and locked in place.
A non-contact lap (when rebar is close but doesn’t actually touch) also creates a continual line of reinforcement. When using this method, the space between bars should not exceed 1/5th the lap splice length (typically 40 times the bar diameter or 6″, whichever is less).
The rebar finger design prevents the rebar from popping back out after they are locked in place. This delivers the same result as tying rebar while saving time and money. The rebar surface area is reduced when it is stacked in web channels. This allows concrete to easily flow around rebar, reducing issues during and after the pour. BuildBlock does recommend tying the top course of rebar at lap splices and where horizontal and vertical bars connect.
The plastic webs keep the rebar in place during vibration as well. Each lift is required to be internally vibrated into the lift below to ensure proper concrete consolidation. Visit the Concrete Reinforcing Steel Institute for a more detailed look at rebar lap splices. Additionally, watch the Reinforcement section of the BuildBlock ICF Installer Training Series to learn about the different forces that concrete is reinforced to withstand and the engineering behind it.
Lastly, more information can always be found in the BuildBlock ICF Installation and Technical Manuals.