Getting Started with ThermoBlock ICF’s

Rebar Placement

ThermoBlock wall systems can be installed on a spread footing and utilized as a stem wall in a foundation system, or installed directly to a slab on grade or grade beam system. Rebar placement in all applications is critical and should be supervised by the wall system installer to for a stronger, cleaner application.

Start rebar placements at each corner and work toward the center of the wall span. Establishment of exact building corners is important and should be performed by a surveying crew or other qualified layout specialist. Once all corners are established and building is checked for square, start placement of rebar 4” in from corner in both directions, establishing the corner rebar as well as center of wall. Set rebar at 8” on center in both directions away from the corner rebar to set corner placement and 16” on center throughout the wall span. Verify this layout is as per engineering report recommendations.


Once rebar is placed per engineer’s recommendations and concrete is placed, it is time to layout the ThermoBlock wall system. In slab on grade or grade beam applications, mark all door and window rough openings and sill heights on slab at their locations. Mark exact openings including space for rough buck frame, (typically 1½” on each side, top and bottom), window/ door rough openings per manufactures recommendations, and any additional shim space that may be required. In spread footing and stem wall applications these locations would be marked at finished floor level on stem wall.


After locating all wall openings, start installation of ThermoBlock wall system. Beginning at corners lay two courses of ThermoBlock around entire perimeter of building placing any cuts required to conform to dimensions on plans in openings of wall or in center of wall as applicable. This vertical seam should be glued together with low expansion canned foam during installation and marked for special attention before grouting, as shown on the next page. Adhesive is only required when the interlocking ends of the block are cut off and isn’t needed in other locations. To create a finished end block for corners and wall ends, one must cut off the tongue on the end of the block and fit it into the groove adjacent to it; typically a friction fit is sufficient to hold it in place. 

At corners, low expansion canned foam is used to seal the butt joint of the block where the tongue and groove have been removed. It is also necessary to remove the two sections of foam at the top of the block in the course below. This allows the block to interlock at each corner alternating every other course.

Straight Line

Once the first two courses are set and interlocked, it is time to straight line the wall. Using a typical mason’s line block set on the top corner of the second course, set each wall section in a straight line. Take care to insure the line is tight and not bound at any point. After the wall in straightened, install approximately 2” of job mixed concrete (premixed concrete of 300 psi or better) in each cell that has rebar stubbed out vertically in it, as shown below. This establishes and holds the wall in a straight line and can be used to level the first two courses by lifting low block to string line and allowing concrete to flow under the block as well. Work your way around the entire structure until all walls are straight and level to the second course. Allow concrete to gel.


When the first two courses of ThermoBlock are set straight and level and concrete has gelled, it is time to set rough buck frames for doors and windows, as shown. Install pre-built units for doors and brace with 2X4 to the ground outside the building. Be sure bucks are level and plumb, utilizing screws to attach braces to bucks and stakes. This will facilitate removal of braces without damage to bucks once concrete is poured. Window bucks are set once sill heights have been reached. The area below sills should have IBS installed and concrete poured in them, as shown, before sill is set or holes will have to be drilled in bucks to accommodate grouting. In many applications, the engineer will require a bond beam at the sill of each window opening. This bond beam should extend into the wall on both sides and tie to a vertical rebar in grouted posts on adjacent sides of the opening.