Under-slab insulation: actual board, layer order and perimeter receiving checks
A distribution warehouse has boards and an under-slab sheet placed in the order used on the previous job. The current detail shows a different arrangement, and the perimeter insulation has not arrived for the pre-pour check.
A slab check needs the current section, including its edges, not only a photograph of boards across the middle. PNNL’s slab-edge guide explains that perimeter connections and different foundation arrangements affect the insulation detail. The actual project must also establish the board’s loading requirements and the order of its sheet or membrane. Do not impose one layer order or one insulation family on every floor.
Check the floor assembly before reinforcement limits access
- Match the actual slab and board requirements. Locate the approved slab section, insulation product, grade, thickness and relevant loading or support criteria. Confirm the receiving base and any required review with the concrete and other responsible teams. Keep a substituted board with its appropriate technical decision. A panel marked with a compressive-strength number is not by itself a design check for concentrated equipment loads or long-term service.
- Confirm the specified layer order and connections. Read where the insulation, sheet, membrane, protection and other layers occur in this assembly. Resolve conflicting drawing and product instructions through the appropriate review before repeating the work. Identify the required seams, penetrations and edge connections separately from board joints. Tape on an insulation joint does not automatically provide the specified vapour, air or water-control function.
- Trace the perimeter and changed slab geometry. Locate slab edges, grade beams, thickened areas, openings and interfaces with the foundation or adjacent floor. Confirm the received insulation extent and permitted termination at each condition. Keep structural and thermal details coordinated; do not insert boards into an unreviewed load path to make a thermal line appear continuous. Missing edge material remains a located question, not something a general field photograph can erase.
- Receive and preserve the checked installation. Arrange the required pre-pour review while joints and interfaces can be inspected. Retain actual product identification, located photos, measured checks and outcomes, including inaccessible limits. Protect the installation during reinforcement, service work and concrete preparation under its actual requirements. Recheck changed or damaged areas before the final handover rather than assuming yesterday’s status covers today’s disturbance.
Common mistakes
- Repeating the previous job’s sheet order.
- Confusing taped board joints with a separate control layer.
- Ignoring slab edges or changed loading conditions.
- Using an earlier check after the installation is disturbed.
Checklist
Before concrete, retain
- Current slab section and exact board identity.
- Relevant load, support and receiving-base requirements.
- Received layer order and separate sheet connections.
- Located perimeter and changed-geometry details.
- Actual review outcomes and rechecked disturbance.
Check your understanding
The field boards are down, but edge insulation is missing. Is the slab insulation complete?
Show the answer
Check the current perimeter requirements and retain the missing areas as unresolved until the appropriate response and receiving checks are complete. A central field photograph does not establish the edge detail or authorize a pour past a required hold.
