Seal and Insulate Rim Joists

A. Finished-Project Specification

Deliverable: every assigned rim-joist bay fitted with a correctly sized rigid-foam insert, sealed continuously at its perimeter, with service penetrations sealed, required inboard batt insulation installed where specified, exposed foam protected with the required thermal or ignition barrier, termite-inspection gaps preserved, and service access maintained.

B. Bay Schedule

Bay	Included Elements	Excluded Unless Cleared
Standard bay	Rigid-foam insert, perimeter seal, inboard batt where specified	Bays with active water entry or decay requiring repair
Penetration bay	Foam insert cut and sealed around plumbing, electrical, or duct penetrations per Chapter 4 methods	Penetrations with damaged wiring or leaking plumbing
Termite-inspection bay	Foam and sealant installed above the required gap only	Any closure of the required inspection strip
Combustion-clearance bay	Noncombustible blocking and high-temperature sealant per Chapter 5 and 13 requirements	Foam or combustible sealant within the clearance zone

C. Material Takeoff

• Rigid foam: approved product, thickness, and quantity sufficient for every assigned bay, calculated from individual bay measurements rather than an estimated average.
• Perimeter sealant or approved one-component foam: quantity sufficient for a continuous bead around every foam insert and at every penetration.
• Ignition-barrier or thermal-barrier material: quantity sufficient to cover every exposed foam surface where the approved assembly requires it.
• Fasteners or adhesive: type and quantity specified by the approved assembly for holding the foam insert in place before sealing.

D. Acceptance Standards

Check	Standard
Moisture condition	Every bay confirmed dry by moisture meter before foam is installed; no bay insulated over an unresolved water source
Foam fit	Every foam insert cut to leave a controlled, consistent perimeter gap sized for the specified sealant or foam
Perimeter seal	Continuous, fully tooled bead of compatible sealant or approved foam around every insert with no gaps, pinholes, or skips
Penetration seal	Every service penetration sealed per Chapter 4 methods without bonding valves, unions, or serviceable joints
Termite gap	Required termite-inspection gap fully visible and unobstructed in every bay where required by the jurisdiction
Fire protection	Every exposed foam surface covered by the required thermal or ignition barrier where the approved assembly specifies one
Access	Anchor bolts, valves, electrical boxes, and inspection zones remain visible and reachable in every bay

E. Preparation — Review and Inspection

1. Review the rim-joist assembly, exterior sheathing, foundation, sill, termite requirements, climate strategy, foam product, and fire-protection requirements. Confirm the approved foam type, thickness, ignition-barrier system, and required termite-inspection gap before entering the work area.
2. Inspect the rim and sill for water staining, rot, insects, corrosion, foundation leakage, and exterior flashing defects. Use the moisture meter at the sill and rim in every bay and record each reading on the worksheet.
3. Stop work for active water entry, structural decay, termite activity requiring inspection, hazardous materials, or damaged wiring. Record the affected bay as excluded, state the specific reason, and identify the qualified professional required before work can proceed in that bay.
4. Identify service penetrations, electrical boxes, joist hangers, anchor bolts, ducts, and combustion-clearance zones. Record each item and its location for every bay on the worksheet before cutting any foam.

F. Substrate Preparation and Measurement

1. Clean loose dust and debris from the rim and surrounding framing. Vacuum each bay before measuring so the foam insert seats against a clean surface.
2. Measure each bay independently. Record width and height at both the top and bottom of the bay, since rim-joist bays are frequently out of square.
3. Cut rigid foam slightly smaller than the bay to create a controlled sealant joint. Cut using the manufacturer-approved method for the specified foam product, and verify the resulting gap is consistent on all four sides.
4. Verify foam type, thickness, vapor characteristics, ignition-barrier requirement, and substrate compatibility. Confirm the cut insert matches the approved product specification before fitting it into the bay.

G. Fitting, Sealing, and Termite-Gap Preservation

1. Fit the foam against the approved surface without trapping active moisture. Confirm the moisture reading for the bay one final time immediately before fitting the insert.
2. Maintain required termite-inspection gaps where applicable. Position the foam insert so the required inspection strip remains fully visible and unobstructed.
3. Seal the foam perimeter continuously with compatible sealant or approved one-component foam. Tool the bead into full contact with both the foam edge and the surrounding framing on all sides.
4. Seal service penetrations using Chapter 4 methods. Apply the compatible sealant, gasket, or firestop system identified for each penetration type without bonding serviceable joints.

H. Inboard Insulation and Fire Protection

1. Install additional batt insulation inboard of the foam only when the approved assembly requires it. Fit the batt snugly against the foam without compressing it, and confirm the facing orientation matches the approved vapor-control design.
2. Do not place air-permeable batt alone against a leaky rim without the specified air barrier. Confirm the foam-and-sealant air barrier is complete and cured before installing any inboard batt.
3. Protect exposed foam with the required thermal or ignition barrier. Install the barrier material per the manufacturer instructions, covering every exposed foam surface specified by the approved assembly.

I. Access Preservation and Inspection

1. Preserve access to anchor bolts, valves, electrical boxes, and inspection zones. Confirm each identified item from Step 4 remains visible and reachable after foam and sealant installation.
2. Inspect edge seals, foam fit, fire protection, moisture condition, and continuity between bays. Check every bay individually rather than sampling a subset.
3. Correct gaps, loose inserts, incompatible foam, or missed penetrations. Remove and refit any insert that does not meet the Acceptance Standards table before proceeding.
4. Document product, thickness, bay locations, termite gap, and protection method. Complete the worksheet entry for every bay, including product lot information and photographs of each bay before concealment.