Flooring Installation Inspection

Per ASTM F710 and NWFA Installation Guidelines, subfloors must be flat to within 3/16 inch in 10 feet for glue-down installations and 3/16 inch in 6 feet for mechanically fastened installations. Concrete subfloors must have a minimum compressive strength of 3,000 psi. Plywood subfloors must be a minimum 3/4-inch tongue-and-groove, properly fastened to joists at 6 inches on center along edges and 12 inches in the field per APA recommendations.

1. Place a 10-foot straightedge on the subfloor in multiple directions and measure gaps with a feeler gauge — maximum 3/16 inch deviation allowed per NWFA guidelines

2. Verify plywood subfloor thickness is at least 3/4 inch and panels are staggered with 1/8-inch expansion gaps between sheets

3. Check for squeaks, loose panels, and fastener pops by walking the entire subfloor area

4. Confirm concrete subfloor is free of curing compounds, sealers, adhesive residue, and other bond breakers per ASTM F710

5. Verify wood subfloor is structurally sound with no delamination, rot, or excessive deflection (L/360 minimum per IRC Section R301.7)

- Subfloor not flat enough causing lippage, hollow spots, or telegraphing of imperfections through resilient flooring

- Plywood panels butted tightly with no expansion gap leading to buckling

- Residual adhesive or curing compound on concrete not removed prior to installation

- Inadequate fastening of plywood subfloor causing squeaks and movement

- Concrete subfloor not properly profiled or patched before flooring installation

Per ASTM F2170, in-situ relative humidity (RH) probe testing of concrete slabs must read at or below 75% RH (or per manufacturer specifications) at 40% depth of a single-sided drying slab. Per ASTM F1869, calcium chloride testing must not exceed 3 lbs per 1,000 sq ft per 24 hours for most resilient and wood flooring products. The NWFA requires wood subfloor moisture content to be between 6% and 9%, and the moisture content difference between the subfloor and hardwood flooring must not exceed 2% for strip flooring or 4% for plank flooring wider than 3 inches.

1. Perform ASTM F2170 RH probe testing on concrete slabs — drill test holes to 40% of slab depth, insert probes, and allow 72-hour equilibration before reading

2. Conduct ASTM F1869 calcium chloride testing on concrete — seal test kits for 60-72 hours and weigh moisture gain; maximum 3 lbs/1,000 sq ft/24 hrs for most products

3. Use a pin-type moisture meter on wood subfloors to verify moisture content is within 6-9% range per NWFA guidelines

4. Check that the moisture content difference between the wood subfloor and the hardwood flooring does not exceed the NWFA 2%/4% differential limits

5. Verify a Class 1 vapor retarder (0.1 perm or less) is installed over concrete slabs for nail-down hardwood installations per NWFA guidelines

6. Document all moisture test results with locations, dates, and ambient conditions for warranty compliance

- Concrete slab not allowed adequate curing time (minimum 60 days) before testing

- Calcium chloride test conducted on slabs with radiant heating or recent surface treatments giving inaccurate results

- Failing to test enough locations — ASTM F2170 requires minimum 3 tests for the first 1,000 sq ft plus 1 per additional 1,000 sq ft

- Wood subfloor moisture differential exceeding NWFA limits causing post-installation cupping or crowning

- No vapor retarder installed between concrete slab and hardwood flooring

Per NWFA Installation Guidelines, solid hardwood strip flooring (up to 3-1/4 inches wide) must be blind-nailed with fasteners spaced every 6-8 inches along the length, 1-2 inches from end joints, and within 3 inches of each board end. A minimum 3/4-inch expansion gap must be maintained at all walls, vertical obstructions, and transitions per NWFA standards. Boards must be installed perpendicular to floor joists or at a 45-degree angle when installed over plywood subfloors. End joints in adjacent rows must be staggered a minimum of 6 inches.

1. Verify expansion gap of 3/4 inch is maintained at all walls and vertical obstructions — check behind baseboards and at transitions with a tape measure

2. Measure fastener spacing to confirm 6-8 inch intervals along board length with fasteners 1-2 inches from end joints per NWFA guidelines

3. Confirm end joints are staggered a minimum of 6 inches between adjacent rows and distribution appears random (H-pattern joints are not acceptable)

4. Check that boards are tight with no visible gaps exceeding the thickness of a business card (approximately 0.010 inch) at side joints

5. Inspect for proper racking — verify short boards are not clustered and boards are selected from multiple cartons during installation

- Insufficient expansion gap at walls causing buckling or tenting during seasonal humidity changes

- Fasteners overdriven or underdriven causing splits, squeaks, or loose boards

- End joints aligned in adjacent rows creating a staircase or H-pattern appearance

- Boards not acclimated to job-site conditions for the NWFA-recommended minimum of 3-5 days before installation

- Improper fastener angle (45 degrees through the tongue) causing splits at board edges

Per NALFA (North American Laminate Flooring Association) Installation Standards and manufacturer specifications, laminate flooring must be installed as a floating floor with a minimum 1/4-inch expansion gap at all walls and fixed objects. Underlayment must be installed per manufacturer requirements, with seams taped and a 6-mil polyethylene vapor barrier over concrete subfloors. Engineered hardwood may be glued, nailed, or floated per NWFA Engineered Wood Flooring Installation Guidelines. All products must be acclimated in the unopened cartons at the installation site for a minimum of 48 hours with the HVAC system operational and maintaining 60-80°F and 30-50% relative humidity.

1. Verify a minimum 1/4-inch expansion gap is maintained at all walls, doorframes, transitions, and fixed objects such as cabinets and island bases

2. Confirm underlayment is properly installed with seams butted (not overlapped, unless manufacturer specifies otherwise) and taped, and a 6-mil vapor barrier is present over concrete subfloors

3. Check locking mechanism engagement by attempting to lift joints — boards should not separate or show visible gaps at click-lock connections

4. Verify acclimation documentation confirms product was stored on-site at 60-80°F and 30-50% RH for a minimum of 48 hours before installation

5. Inspect for proper staggering of end joints — minimum 8-inch offset for laminate (or per manufacturer specifications) and 6 inches for engineered hardwood

- Expansion gaps blocked by baseboards fastened too tightly or T-molding nailed through the floating floor

- Underlayment seams overlapping causing raised ridges telegraphed through the laminate surface

- Locking joints not fully engaged resulting in gaps that worsen over time

- Product not acclimated causing excessive expansion or contraction after installation

- Transition moldings not installed at doorways between rooms exceeding manufacturer maximum continuous run length

Per ASTM F1303 (Standard Specification for Sheet Vinyl Floor Covering with Backing) and ASTM F1700 (Standard Specification for Solid Vinyl Floor Tile), resilient flooring must be installed over subfloors prepared in accordance with ASTM F710. Adhesives must comply with the manufacturer's specifications and applicable VOC limits. For glue-down installations, the adhesive must achieve proper tack before setting planks. Luxury vinyl plank (LVP) floating installations require a minimum 1/4-inch expansion gap at all perimeter walls and fixed objects. Subfloor temperature must be maintained between 65°F and 85°F for a minimum of 48 hours before, during, and after installation.

1. Verify subfloor flatness meets ASTM F710 requirements — 3/16 inch in 10 feet for glue-down resilient products and 1/8 inch in 6 feet for rigid-core LVP where specified by manufacturer

2. Confirm adhesive type and spread rate match manufacturer specifications — check with a trowel notch gauge and verify open time was observed before setting planks

3. For floating LVP, verify 1/4-inch expansion gap at all walls, columns, and transitions and confirm no adhesive or fasteners are securing the floor to the subfloor

4. Check that seams are tight with no visible gaps, lippage, or peaking at plank edges — use a straightedge to verify flush transitions between planks

5. Verify subfloor and room temperature was maintained at 65-85°F for 48 hours before and during installation per manufacturer requirements

- Adhesive applied with incorrect trowel notch size resulting in insufficient bond or oozing at seams

- Glue-down vinyl installed before adhesive reached proper open tack time causing bubbles or poor adhesion

- Subfloor imperfections telegraphing through thin resilient sheet goods (insufficient patching per ASTM F710)

- Floating LVP installed with no expansion gap causing buckling at walls during temperature changes

- Product installed over radiant heat systems without verifying manufacturer approval and maximum surface temperature limits

Per CRI 104 (Standard for Installation of Commercial Carpet) and CRI 105 (Standard for Installation of Residential Carpet), carpet must be power-stretched using a power stretcher (not a knee kicker alone) to achieve a minimum 1-1.5% stretch in both directions. Seams must be sealed with seam sealer and joined using hot-melt seam tape with a seaming iron at proper temperature per adhesive manufacturer specifications. Tackless strip must be installed around the perimeter with a gutter space of approximately 2/3 the carpet thickness between the strip and the wall. Padding must meet the minimum density and thickness requirements specified by the carpet manufacturer and CRI Carpet Cushion Standards.

1. Verify carpet is power-stretched in both directions — press firmly in the center of the room and check for wrinkles, ripples, or excess movement indicating inadequate stretch

2. Inspect all seams by running fingers along the joint — seams should be tight with no visible gaps, fraying, or peaking, and seam orientation should run toward the primary light source

3. Confirm padding is the correct density and thickness per carpet manufacturer warranty requirements and seams are taped (not overlapping) with edges butted tightly

4. Check tackless strip installation — strips should be positioned with a gutter space of 2/3 carpet thickness from the wall and pins angled toward the wall

5. Verify transitions at doorways include proper edge strips or transition moldings and carpet is securely tucked at all edges

- Carpet stretched with knee kicker only instead of power stretcher causing wrinkles and premature wear per CRI 104/105

- Seams placed in high-traffic areas or oriented perpendicular to the primary light source making them highly visible

- Incorrect padding density or thickness voiding the carpet manufacturer's warranty

- Seam tape not fully activated causing seam separation and fraying over time

- Carpet not properly tucked into gutter space resulting in edges pulling away from walls

Per ADA Standards for Accessible Design (Section 303), changes in floor level up to 1/4 inch may be vertical, and changes between 1/4 inch and 1/2 inch must be beveled at a maximum slope of 1:2. Reducer strips, T-moldings, and transition thresholds must comply with these accessibility requirements at all doorways and flooring material changes. Per NWFA Installation Guidelines, baseboards and quarter-round must not be fastened to the flooring itself but to the wall to preserve the expansion gap. All transition moldings must be securely fastened per manufacturer specifications, and stair nosing must comply with IRC Section R311.7.5 and NWFA stair installation guidelines for overhang and profile requirements.

1. Measure height differences at all transitions between flooring types — verify changes do not exceed 1/2 inch and any change between 1/4 inch and 1/2 inch is beveled at 1:2 slope per ADA Section 303

2. Confirm reducer strips and T-moldings are securely fastened to the subfloor (not to the floating floor) and that expansion gaps are maintained beneath the molding track

3. Verify baseboards and quarter-round are fastened to the wall only, not pinning the flooring, to allow seasonal expansion and contraction per NWFA guidelines

4. Inspect stair nosing for proper overhang (3/4 inch to 1-1/4 inch per IRC R311.7.5) and confirm it is securely fastened with no flex or movement under foot traffic

5. Check that all transition pieces are flush-fitting with no visible gaps, sharp edges, or trip hazards at doorways and room boundaries

- Transition strips creating a height change greater than 1/2 inch violating ADA accessibility requirements

- T-moldings or reducer strips nailed through floating floors preventing expansion and causing buckling

- Missing transitions at doorways between rooms where different flooring types meet

- Stair nosing with excessive overhang or inadequate fastening creating a safety hazard

- Baseboards nailed through the flooring pinning it to the subfloor and eliminating the expansion gap