ICF Installation

Site Preparation & Excavation 1-2 days

The starting point is everything. A poorly-prepared site produces a poor foundation regardless of how carefully the rest of the install proceeds.

What happens:

• Final site survey — setbacks confirmed, building corners staked, utility locates verified
• Excavation — remove organic material (topsoil, roots, debris) from the building footprint and a working margin around the perimeter (typically 1m beyond foundation lines for working space)
• Achieve correct depth — top of footing typically 1.4-1.5m below finished grade in central Simcoe County, deeper in snow belt areas. OBC minimum frost depth is 1.2m but local municipalities require deeper based on regional conditions
• Ontario frost depth by region: Central Ontario (Barrie, Peterborough, Kingston) 1.2-1.4m; Georgian Bay snow belt (Collingwood, Wasaga, Tiny, Penetanguishene) 1.4-1.5m; Ottawa Valley 1.4-1.5m; Northern Ontario 1.5-1.8m
• Bottom of excavation graded level and compacted — geotechnical inspection if required by engineer or municipality
• Drain rock placed where weeping tile will sit; sump pit prep if applicable

What can go wrong:

• Excavation not deep enough — frost heave risk over 30+ year service life
• Insufficient working margin — cramped crew movement during install
• Organic material left in place — settlement risk under footings
• Drainage not prepared — water management problems compound through the project

Footings 1-2 days

Footings transfer building loads to the soil and provide the level base for the ICF wall to start on. They must be wide enough to distribute loads and reinforced enough to span minor soil irregularities.

What happens:

• Footing forms set — typically 400mm wide × 200mm deep for an 8″ ICF wall (per OBC Part 9 tables or engineer specification)
• Footing reinforcement — 15M longitudinal bars (typically 2-3 bars depending on footing width), 10M ties at corners. Reinforcement per CSA A23.3 for engineered designs.
• Vertical dowels for ICF wall connection set at the correct spacing matching the wall’s vertical rebar schedule — typically 15M at 600mm o.c., extending approximately 600mm above the top of footing
• Concrete pour — 20-25 MPa typical residential per CSA A23.1 (often 25 MPa for footings to allow earlier loading). Air-entrained 5-8% for freeze-thaw resistance.
• Level critical — achieve within 6mm (1/4″) of level across the footing surface. Out-of-level footings make the entire wall stacking sequence harder.
• Cure period — 24-48 hours before wall stacking begins; longer in cold weather
• Radon stub installation — new 2024 OBC requirement for all new homes; sub-floor depressurization pipe installed at this stage in some sequences (or with slab pour, depending on builder)

What to verify:

• Footing dimensions match wall thickness specification (wider for larger ICF cores)
• Dowel spacing matches the wall’s vertical rebar schedule exactly — mismatches mean field bending or splicing
• Dowel length adequate for proper lap with wall vertical rebar (typically 600mm minimum lap)
• Footings square to design layout — minor squareness errors compound over the wall stack

First Course of ICF Blocks 1 day

The most critical course of the entire wall. Everything stacked above the first course inherits its alignment, level, and squareness. Spend extra time here.

What happens:

• Corner blocks first — place all corner blocks at the four corners (or more for complex floor plans), aligned to chalk lines on the footing
• String lines — pulled corner-to-corner to define wall lines for placing intermediate blocks
• Straight blocks — laid working from each corner toward the centre of each wall segment, with vertical dowels passing through the corresponding webs
• Level adjustment — shims placed beneath blocks to bring the first course to consistent level; some installers use mortar bed leveling for footings that are out by more than 13mm
• Connection — some installers use zip ties or rebar tie wire to pull blocks snugly together at the seams; major brands have interlock that handles this without ties if properly placed
• Verify square — measure diagonals corner-to-corner; should match within 6mm for a typical residential rectangular footprint
• Horizontal rebar — place 15M horizontal bars in the designated clips at the top of the internal webs (per CSA G30.18 designation)

Why this course is critical:

• Any out-of-square error compounds upward through all subsequent courses
• Out-of-level errors require corrective shims or rip cuts that slow the whole install
• Misaligned dowels mean rebar can’t pass cleanly through web slots without bending
• Spending an extra hour here saves a day later

Subsequent Courses, Bucks, and Bracing 2-3 days

After the first course is set, the wall builds up quickly — if you stay disciplined about running bond, opening detailing, and bracing.

What happens:

• Running bond pattern — reverse the orientation of corner blocks on the second course so seams don’t line up vertically; same pattern for all subsequent courses. This is what gives ICF walls their inherent structural strength against shear loads.
• Level check every 2-3 courses — small errors accumulate; verify with a long level or laser before they compound
• Window and door bucks — install wood or metal frames into openings as the wall rises. Bucks must be plumb, square, and sized to the window/door manufacturer’s rough opening. Concrete bonds to the buck during the pour, so the buck stays in place permanently.
• Service penetrations — electrical conduits, plumbing penetrations, HVAC sleeves, mechanical openings — all installed during stacking before concrete pour. Post-pour penetrations require concrete coring and are significantly more expensive.
• Bracing installation — steel or wood bracing every 1.2m (4′) along the wall perimeter, with adjustable turnbuckles for plumbing the wall. Bracing must be plumbed perfectly before the pour — the wall will follow whatever the bracing says.
• Lintel preparation — for spans exceeding OBC Part 9 prescriptive limits, engineered lintel design with additional rebar and proper concrete cover. See our ICF lintel design guide for details.
• Top course — the final course uses taper-top blocks that prevent concrete intrusion into the interlock and produce a level wall top for sill plate installation

Reinforcement Placement Concurrent with stacking

Steel reinforcement isn’t a separate phase — it’s placed as the wall stacks. But the spec details are critical for structural performance.

Canadian rebar designations (CSA G30.18):

Standard Ontario residential ICF reinforcement:

• Vertical bars — 15M @ 600mm (24″) o.c., lapped into footing dowels and continuous to wall top
• Horizontal bars — 15M @ 400mm (16″) o.c. vertically (typically every second course of an 18″-high block)
• Additional reinforcement at openings — 2-3 bars above and below windows and doors, plus diagonal corner bars at openings
• Corner reinforcement — bent corner bars overlapping vertical bars from each wall direction, providing continuity around the corner
• Concrete cover — 40mm minimum from rebar surface to concrete face per CSA A23.1 (important for lintel design too)
• Splice lengths — minimum 600mm lap between rebar segments per CSA A23.3

For engineered designs (walkouts, taller walls, unusual conditions, multi-storey), a structural engineer specifies the exact reinforcement schedule per CSA A23.3. For prescriptive Part 9 designs (most residential), OBC tables specify the reinforcement based on soil retention height. See our complete 2024 OBC guide.

The Concrete Pour 1 day (4-6 hours of pour)

The moment of truth. Everything you’ve set up in steps 1-5 either works or doesn’t at this point. A well-prepared wall poured properly is uneventful. A poorly-prepared wall poured aggressively can blow out the foam, deflect, or honeycomb.

Pre-pour checklist:

• All bracing verified plumb and locked
• Rebar in correct positions, with proper laps and corner ties
• Window and door bucks properly braced internally to resist concrete pressure
• Service penetrations all in place
• Anchor bolts laid out at top of wall for sill plate connections
• Pump truck access confirmed, pump truck size appropriate for site (boom or line pump)
• Concrete truck schedule confirmed with supplier (3-4 trucks for typical residential basement)

Concrete specs (CSA A23.1 standard):

• Strength: 25-30 MPa typical for residential ICF walls (above OBC Part 9 minimum of 20 MPa)
• Slump: 150-200mm — flowable enough to fill the form without honeycombing, not so wet that hydrostatic pressure deforms the foam
• Aggregate size: 10-14mm — matches the form cavity geometry without bridging at rebar locations
• Air entrainment: 5-8% for freeze-thaw resistance

Pour sequence:

• Start at corners — pour from corners working outward, ensures clean fill at the most structurally critical points
• Lift sequence — pour in 1.2m (4′) lifts, not full height continuously. Allow brief pause between lifts to let lower lift begin set. This manages hydrostatic pressure.
• Vibration — light internal vibration (pencil vibrators) ensures concrete fills around rebar and around openings without honeycombing. Avoid excessive vibration — over-vibrating can liquefy the concrete and increase pressure on the foam.
• Monitor wall alignment continuously — have one crew member walking the perimeter checking plumb and adjusting turnbuckles as needed
• Top finish — wall top struck off level for sill plate or anchor bolts; anchor bolts set per spec while concrete is still plastic
• Total pour time — usually 4-6 hours for a typical 1,800-2,400 sq ft home foundation; longer for walkouts

Embedments and Floor Integration Concurrent with pour or shortly after

Things that need to be embedded in the concrete have to happen during or right after the pour — once concrete cures, you can’t add embedded fastenings without coring.

What gets embedded:

• Anchor bolts for sill plate — set into the top of the wall while concrete is plastic. Spacing per OBC Part 9 (typically 2.4m / 8′ o.c. maximum, closer if seismic or wind design requires)
• Hangers for floor joists — if floor joists bear into wall pockets formed in the ICF, ledger boards and joist hangers attach via concrete anchors after cure
• Beam pockets — for engineered floor systems where steel or wood beams need to bear directly on the wall
• Floor system attachment points — depending on the floor system (wood I-joists, engineered lumber, steel, concrete topping), specific embeds may be required
• Future deck or porch ledger anchors — if exterior deck/porch is in the design, ledger anchors set during pour are far better than retrofit concrete anchors

Floor system integration after wall cure:

• Wood floor system — engineered I-joists or dimensional lumber bear on the sill plate, which is anchored to the top of the ICF wall
• Engineered steel floor — web steel or open-web steel joists bear on top of wall or via pockets formed during the pour
• Concrete floor topping (if specified) — poured separately after wall cure, with appropriate flashing and isolation

Finishing, Waterproofing, and Backfill 3-4 days

The work that protects everything you just built. Skip these steps or do them poorly, and the wall’s 100-year service life gets compromised.

What happens (in sequence):

• Bracing removal — after concrete reaches initial set (typically 24-48 hours; longer in cold weather). Don’t rush this — premature bracing removal can cause walls to lean.
• Exterior waterproofing — self-adhesive rubberized asphalt membrane or liquid-applied membrane on exterior foam surface. Critical for below-grade walls. Some brands have specific compatible systems.
• Drainage board / dimple membrane — applied over the waterproofing to allow water to travel down to the weeping tile rather than pooling against the wall
• Drainage tile (weeping tile) — 4″ perforated pipe at footing level, wrapped in filter sock, surrounded by clean stone, draining to daylight or sump pit
• Backfill — clean granular stone (300mm minimum) against the wall, then compacted granular and final native soil to grade. Backfill in lifts compacted to 95% Standard Proctor Density.
• Grading — surface grade slopes at least 5% away from the foundation for the first 1.5m (5′) from the wall
• Underslab insulation and prep — R-10 minimum continuous foam, vapour barrier, slab reinforcement (mesh or fiber). Radon depressurization stub completed.
• Slab pour — 100mm typical residential slab, finished smooth or broom-textured per use