Headers and Bond Beams

The philosophy behind ICF wall systems is that the blocks act as forms for the steel-reinforced concrete that is poured into them, and then the blocks remain to provide insulation. They are therefore referred to by engineers and building officials as stay-in-place forms . A really good wall system, like ours, will also provide interior and exterior surfaces ready for the materials that will be applied to them.

The problem that all wall systems must solve is how to build a wall that is structurally sound and well insulated, but will also support the load over openings in the wall, such as those required by doors and windows.

Almost all of the current ICF systems, except ours, solve this problem by making the wall so strong that you can cut an opening for a door or window in it, and the portion of wall that remains over the opening will support the weight above it. The downside to this compromise in design is that even though the load over doors and windows is supported, the wall everywhere else is overbuilt.

It is important to remember that every teaspoon of unnecessary concrete that goes into a wall is a reduction in insulation. When we designed our wall system, we were driven by two things: we wanted a wall that was extremely strong, and we wanted a wall that was highly insulated.

The Tech Block header block is our solution to the problem posed by these two opposite desires. Our header blocks form a concrete bond beam inside the wall only at those areas that need it - over doors and windows - and nowhere else. This means that our wall system isn't massively overbuilt where it doesn't need to be.

Our header blocks get installed like any other block, and they get filled with grout along with the rest of the wall. And, they can be used in combination for larger spans and loads. The drawings below illustrate this:

We use a single header block at the top of every wall whether there is an opening below it or not. This single header, shown in Detail H-1, forms a continuous bond beam around the top of the wall, which adds great strength to the wall and will usually support the load over small doors and windows.

So essentially, our header design maximizes the energy efficiency of our wall system by strengthening only the areas that need it. The determination of which header design to use is made by our structural engineer, who will factor in such influences as snow load, wind, roofing material, truss span, and seismic zone in order to call out the particular header configuration that's needed for a given location.

When we have a load/span that is too great for the single header block, we can double them as shown in Detail H-2. This bond beam will usually span openings as wide as 8/0 windows. If we need to, we can beef up the rebar and add stirrups, as shown in Detail H-3, to span openings as wide as single-car garage doors.

Openings larger than what we can span with a beefed-up double header, such as two-car garage doors, are supported by the I-beam method shown in Installation manual 8.