ICF Formwork for a Parallelogram Foundation

Out of square on purpose: Here's how carpenters create the custom formwork to realize an architect's vision.

Footing Form

Excavating the sloped site was complicated by rocky ledge just below the surface. The crew built stepped wooden footing forms to conform to the grade.

Footing Form

Here's a view of the stepped wooden footing forms with rebar in place, before the concrete is placed.

Poured Footings

Here's a view of the concrete footings after the footing pour.

Footings in Place

Here's another look at the freshly poured concrete footings, before wooden forms are stripped.

Capillary Protection

Carpenter Dale Cunningham applies polymer waterproofing to the top of the freshly placed footing.

Pier Footing Forms

The crew built wooden forms for the pier pads and placed rebar cages.

Pour Pier Pads

Half the house will be supported by concrete piers, with an insulated floor spanning between supports. Here is a look at the freshly poured spread bases for the piers.

Perimeter Footings in Place

Here's a view of the completed perimeter footing, with forms stripped, ready for placement of ICFs.

ICF Base Course

Carpenter Dale Cunningham works on the ICFs for the perimeter foundation.

Forming a Square Corner

Lead carpenter Mark Pollard places an ICF corner piece at one of the square corners of the perimeter foundation.

Extending the Wall

Working from the corner outward, Pollard places an ICF piece along the run of the foundation wall.

Piecing In

Pollard cuts a short section of ICF (left) and fits it into the remaining gap in a stretch

Bending Rebar

The ICF sections come with integral plastic bracing that also serves to position and hold the steel reinforcement for the wall (and also serves as an attachment point for bracing). Here, Pollard and Cunningham bend a piece of rebar after setting a course of ICF blocks.

Reinforcing Steel

Pollard and Cunningham carry a piece of rebar over to the wall after bending it to match the wall corners.

Placing Rebar

Pollard and Cunningham fit a bent piece of reinforcing steel into place in the ICF.

Odd Angles

The challenge with this house is to form the non-square angles for the building's parallelogram foundation footprint — one open angle that is greater than 90 degrees (left), and one acute angle that is less than 90 degrees (right).

Scribing an Odd Angle

Pollard lays out the non-square miter angle on a section of ICF.

Cutting the Miter

Pollard cuts the out-of-square miter on the polystyrene form block with a handsaw.

Constructing the Corner

Pollard places a corner ICF block.

Matching Miters

Pollard and Cunningham work on fine-tuning the open-angled corner.

Reinforcing the Corners

Standard right-angle ICF corners are made with manufactured one-piece corner blocks, and require no special reinforcement. But these custom out-of-square corners have to be stiffened and secured with braced OSB panels.

Forming a Step-Down

The crew formed up a corner step-down dam with OSB and 2x lumber.

Reinforced Corner

Here's another look at the reinforced open corner and step-down dam.


After setting and reinforcing the ICF wall forms, the crew attached bracing and a simple working platform around the foundation perimeter.

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