RC Frames
QA inspection checklist

Reinforcement

1. 1.

   Rebar size, grade, and spacing match drawings
   What to look forBar marks (e.g. T16, B12) match the bar bending schedule. Spacing measured between adjacent bars (not centre-to-centre at edges). Top and bottom mats clearly distinguishable. Mark tags from supplier visible on bundles.
   Acceptable whenRebar grade B500B (typical UK structural) per BS 4449. Bar spacing tolerance ±10 mm or ±5% (whichever larger) per BS 8666 / NSCS. Schedule matches bar bending schedule revision noted on drawing.
   StandardBS 4449:2005+A3:2016 — Steel for reinforcement. BS 8666:2020 — Scheduling, dimensioning, bending and cutting. BS EN 1992-1-1 (Eurocode 2).
   Common defectsWrong bar size used (T12 instead of T16) — visible in bar markSpacing pulled tight at one location to fit a bar in — gap elsewhereTop mat dropped because chairs collapsed — bar in compression zoneMild steel (R) used where high-yield (T/H) specifiedOld bar bending schedule used — bars no longer fit on revised drawing
2. 2.

   Cover to reinforcement correct

   Record: Cover (mm)
   What to look forCover measured from outermost bar (typically links/stirrups, not main bars) to formwork face. Spacers in place at all faces — top, bottom, sides. Cover blocks of correct depth, not random offcuts. No bars touching formwork.
   Acceptable whenNominal cover per Eurocode 2 / NSCS — typical interior 25 mm, exterior 35-45 mm, in-ground 50-75 mm. Tolerance Δcdev = +10 mm (so design cover = nominal + 10 mm). XC1 exposure 15 mm minimum, XC4 30 mm minimum.
   StandardBS EN 1992-1-1:2004+A1:2014 cl.4.4. NSCS — National Structural Concrete Specification. BS 8500-1:2023 — Concrete, exposure classes.
   Common defectsCover insufficient at corners — bars wrapping link too tightlyCover excessive on top of slab — chairs too tall, bar will not engage in compressionSpacers crushed or dislodged during pour — bar drops to formworkWrong cover for exposure class — 25 mm used externally where 35 mm neededCover blocks made on site from concrete offcuts — wrong dimension
3. 3.

   Lap lengths correct per specification

   Record: Lap length (mm)
   What to look forLaps occur in low-stress zones (typically not at midspan or column heads). Bars in contact along the full lap length. Stagger 1.3 lap lengths between adjacent laps in the same plane. Tying wire at minimum two points along each lap.
   Acceptable whenLap length per Eurocode 2 cl.8.7: typically 35-50 × bar diameter for B500B in C32/40 with good bond conditions; e.g. T16 lap ≈ 580 mm, T20 ≈ 730 mm, T25 ≈ 1000 mm. Stagger ≥ 0.3 × lap length apart in same section.
   StandardBS EN 1992-1-1:2004 cl.8.7 — Laps and mechanical couplers. NSCS Section 5.
   Common defectsLap too short — measured by counting bar diametersLaps at midspan in beams — high tension, lap will not developAll laps in same plane — congestion, no concrete penetrationBars not in contact — separated by 50+ mm with no adjustment to lap lengthLap factor not applied for poor bond conditions (top of deep pour)
4. 4.

   Spacers and chairs installed at correct centres
   What to look forChairs at no more than 1 m centres in both directions on slab top mat. Side spacers every 600-900 mm on walls. Plastic or concrete spacers — not timber, brick, or rebar offcuts. Chairs sit on bottom mat without distortion.
   Acceptable whenSpacer centres typically 1 m max for slabs, 600-900 mm for walls and columns per NSCS Section 5. Spacer load capacity adequate for traffic load during pour. Spacers compatible with concrete and exposure class.
   StandardNSCS — National Structural Concrete Specification Section 5. BS 7973 — Spacers and chairs for steel reinforcement.
   Common defectsChairs collapsed under self-weight of operatives — top mat droppedBrick or timber used as spacer — non-durable, will form weaknessSpacers too wide centres — bar sags between supportsPlastic spacer used in fire-rated element — melts during fireNo bottom spacers — bottom bars touching formwork after pour
5. 5.

   Rebar clean — no excessive rust, oil, or mud
   What to look forBars show no flaking rust — light surface rust acceptable and may improve bond. No release agent, oil, paint, or grease on bars. Mud splashes from groundworks washed off before pour.
   Acceptable whenLoose mill scale and flaky rust must be removed (wire brush). Light tight rust acceptable per Eurocode 2 cl.8.3 — does not require removal. No oil, grease, or contaminants. Per NSCS, bar dimensions including rust must remain within tolerance.
   StandardBS EN 1992-1-1:2004 cl.8.3. NSCS Section 5. CIRIA C660 — Early-age thermal cracking.
   Common defectsHeavy flake rust — significant section loss, bars may need replacementForm release agent overspray on cage — reduces bondMud splashes from access route — particularly at column starter barsPaint markings (orange/red) covering more than identification mark
6. 6.

   Coupler connections installed correctly
   What to look forBars fully threaded into coupler — visual sight line at end. Locking nut tight (where applicable). Bars co-axial — no kink at joint. Coupler grade matches bar grade. Manufacturer's torque tool used.
   Acceptable whenCouplers per BS 8597 or CARES approved. Full bar engagement — typically 8 to 12 thread turns visible at far end. Strength ≥ 100% bar UTS. Coupler torqued to manufacturer's figure (e.g. 60-80 Nm for T16).
   StandardBS 8597:2015 — Mechanical splices. CARES Technical Approval Scheme. Manufacturer's installation guidance.
   Common defectsBar not fully engaged — slip under loadWrong coupler size for bar — visible thread mismatchCouplers in tension zone of beam without full strength ratingCross-threaded — installed without thread protector capNo torque verification record

Formwork

1. 7.

   Formwork aligned and plumb

   Record: Deviation (mm)
   What to look forPlumb checked with spirit level or laser at all corners and at intermediate points on long walls. Sheet faces flush, no step at panel joints. Soldier walings straight when sighted along the wall.
   Acceptable whenNSCS Class B (typical fair-faced): plumb ±10 mm in 3 m, line ±10 mm in 5 m, level ±10 mm. Class A higher tolerance for visual concrete: ±5 mm. Eurocode 2 minimum: ±15 mm.
   StandardNSCS — National Structural Concrete Specification. BS EN 13670:2009 — Execution of concrete structures. BS 5975:2019 — Temporary works.
   Common defectsWall out-of-plumb because soldiers not adequately proppedStep at panel joint visible after strike — clamps not tightBow in long walls — insufficient walingsFormwork drifts during pour — props compressing or kicking out
2. 8.

   Formwork joints tight — no grout loss expected
   What to look forSealing tape or rebate at all panel joints. No daylight visible at internal corners. Bottom of wall formwork seated tight to kicker — no gap. Tie-bolt holes have foam plugs or formwork-grade tape.
   Acceptable whenJoints sealed to prevent grout loss per BS EN 13670 cl.5.3. Maximum gap at any joint < 2 mm before pour. Below ground, joints to be water-tight if pour against soil.
   StandardBS EN 13670:2009 — Execution of concrete structures. NSCS Section 4 — Formwork.
   Common defectsGrout loss visible after strike — black streaks down wallHoneycombing at base of wall — gap to kickerBleed water leakage through tie holes — stainingJoint tape missed at panel intersections — typical at corners
3. 9.

   Release agent applied
   What to look forRelease agent applied evenly — visible sheen on form face. No pooling at base. Applied before reinforcement fixing where possible (avoids contamination of bars). Agent type compatible with finish (visual/non-visual).
   Acceptable whenType per NSCS — chemical release agent for fair-faced (Class A), neat oil acceptable for hidden surfaces (Class C). Coverage rate per manufacturer (typically 25-50 m²/litre). No contamination of reinforcement.
   StandardNSCS Section 4. BS EN 13670:2009 cl.5.3.
   Common defectsPooled release agent at base — causes blowholes and weak surfaceDiesel or sump oil used as release — staining and bond failure for follow-on finishesRelease agent on rebar — reduces bondMissed areas — concrete sticks to formwork at strike
4. 10.

   Props and backpropping in place per temporary works design
   What to look forProp layout matches the temporary works drawing. Props adjusted to take load — wedges or screw jacks tight, not loose. Backprops below remain in place until next slab strikes. Sole plates on suspended slabs.
   Acceptable whenDesigned and signed off by Temporary Works Coordinator (TWC) per BS 5975. Prop spacing typically 1.0-1.5 m for slabs depending on thickness. Backpropping for minimum two slab levels on multi-storey RC frames.
   StandardBS 5975:2019 — Temporary works procedural control. CONCRETE Society TR53 — Falsework. BS EN 12812 — Falsework performance.
   Common defectsProps loose — not bearing load, slab will deflect or crackProps removed too early — under-strength concrete failureBackprops dropped one floor too soon — loads cascade to lower slabNo temporary works register or permit-to-loadSingle props instead of pairs at edges — overturning risk
5. 11.

   Kicker cast and correct dimension
   What to look forKicker height typically 75-100 mm. Top of kicker level and clean. Starter bars projecting at correct cover and centres. Surface roughened or scabbled to provide bond key with wall pour.
   Acceptable whenKicker dimensions per drawing — typically 75 mm or 100 mm high. Position tolerance ±10 mm to design line. Top surface scabbled or treated with bonding agent. Concrete grade matches the wall above.
   StandardNSCS Section 4. CIRIA C766 — Control of cracking caused by restrained deformation.
   Common defectsKicker out of line — visible step at floor-wall junctionKicker too low — cannot register wall formworkSmooth kicker top — bond failure at construction joint, water ingressStarter bars dislodged — wall reinforcement compromised

Concrete Pour

1. 12.

   Concrete grade matches specification
   What to look forDelivery ticket inspected before discharge — grade, slump/flow class, exposure class, max aggregate size, cement type. Ticket retained on site. Time loaded to time on site within transport time limit (typically 90 minutes).
   Acceptable whenConcrete designation per BS 8500-2 (e.g. RC32/40, XC1, S3, 20 mm). Delivery to site within 90 minutes from batching for OPC mixes. Temperature at delivery 5-30°C. Quality Scheme for Ready Mixed Concrete (QSRMC) supplier preferred.
   StandardBS 8500-1/2:2023 — Concrete specification. BS EN 206:2013+A2:2021 — Concrete properties. BS EN 13670:2009 cl.8.
   Common defectsC25/30 delivered where C32/40 specified — visible on ticketWrong exposure class — XC1 used where XC4 needed (reinforcement corrosion risk)Concrete > 90 minutes old — workability lost, retempering not allowedCEM I delivered where CEM IIIA (GGBS) specified for sulphate resistanceTicket discarded before inspector sees it
2. 13.

   Slump/flow test carried out

   Record: Slump (mm)
   What to look forSlump cone correctly sampled (composite from at least 4 points across truck). Concrete tamped in three equal layers, 25 strokes each. Cone lifted vertically over 5-10 seconds. Slump measured to nearest 10 mm at highest point.
   Acceptable whenSlump class per BS EN 206: S2 = 50-90 mm, S3 = 100-150 mm, S4 = 160-210 mm, S5 ≥ 220 mm. Tolerance ±30 mm or per specified class. Flow class F4 = 490-550 mm spread (for SCC use slump-flow test).
   StandardBS EN 12350-2:2019 — Slump test. BS EN 12350-5 — Flow table test. BS EN 12350-8 — Slump-flow for SCC. BS EN 206 cl.5.4.
   Common defectsSlump out of class — typically too high, water added on siteTest taken from chute end — not representative of mixCone lifted too fast — collapse looks like high slumpNo slump test on first load of pour — basis for acceptance missingRetempering with water — explicitly prohibited
3. 14.

   Cube samples taken and labelled
   What to look forCubes (typically 100 mm) taken from the same composite sample as the slump test. Labelled with date, pour location, mix reference, and number. Stored under wet hessian or in water tank for first 24 hours, then in curing tank at 20±2°C.
   Acceptable whenSampling per BS EN 12350-1. One sample per 50 m³ or per day per element type, whichever produces more. Minimum two cubes per sample for 28-day test. Identification per BS EN 12390-1.
   StandardBS EN 12350-1:2019 — Sampling. BS EN 12390-2 — Making and curing cubes. BS EN 206 cl.8 — Conformity control.
   Common defectsCubes not taken on first load — common oversightLabels washed off — cubes unidentifiable at the labCubes left on site for several days in poor curing — low resultsSingle cube taken per sample — no redundancy if one failsSampling rate below specified frequency
4. 15.

   Concrete placed and vibrated correctly
   What to look forPour from low height (< 1.5 m typical) or use trunking to avoid segregation. Vibrators inserted vertically, withdrawn slowly when concrete stops bubbling. Insertion at 500-700 mm centres. Layer thickness < 500 mm.
   Acceptable whenFree-fall height ≤ 1.5 m unless stopboard used. Layer depth ≤ 500 mm. Poker spacing 500-700 mm depending on poker diameter. Time at each insertion 10-20 seconds — until air bubbles cease and surface glistens.
   StandardBS EN 13670:2009 cl.8 — Placement and compaction. NSCS Section 7. Concrete Society TR47 — Concrete construction.
   Common defectsFree-fall from > 2 m — segregation, aggregate at basePoker dragged horizontally — pulls air in, weakens concreteOver-vibration — bleed water rise, surface laitanceCold joint — break in pour > 30 minutes without retarderHoneycombing in deep narrow pours — poker did not reach
5. 16.

   Pour temperature recorded

   Record: Temp (°C)
   What to look forConcrete temperature checked at point of placement using probe thermometer. Ambient air temperature also recorded. For mass pours, internal temperature monitored continuously by embedded thermocouples.
   Acceptable whenConcrete placement temperature 5-30°C per BS EN 13670. Below 5°C requires hot concrete or heated formwork; above 30°C requires retarder or chilled water. For mass pours: peak temperature ≤ 70°C, differential < 20°C between core and surface (CIRIA C766).
   StandardBS EN 13670:2009 cl.8.5. CIRIA C766 — Control of cracking caused by restrained deformation. CIRIA C660.
   Common defectsPour above 30°C in summer — accelerated set, plastic shrinkage crackingPour below 5°C — concrete frozen before initial set, no strength gainTemperature not recorded — no evidence of complianceMass pour exceeds 70°C peak — DEF (delayed ettringite formation) riskDifferential > 20°C — early thermal cracking
6. 17.

   Curing method applied as specified
   What to look forCuring started immediately after finishing — typical methods: wet hessian, ponding, plastic sheeting, or curing membrane. Slabs covered before bleed water disappears. Curing maintained for minimum specified period.
   Acceptable whenMinimum curing class per BS EN 13670 Annex F: Class 2 = 35% of 28-day strength, Class 3 = 50%, Class 4 = 70%. Typical UK practice 7 days curing for OPC, longer for GGBS/PFA mixes. Curing membrane to BS 7542.
   StandardBS EN 13670:2009 Annex F — Curing classes. BS 7542:1992 — Curing compounds. NSCS Section 8.
   Common defectsCuring started too late — surface dried out before cover appliedPlastic sheeting blown off in wind — patchy curing, surface crackingCuring compound applied over standing water — film does not sealCuring duration cut short — strength gain inadequateGGBS mix cured for only 3 days — slow strength gain interrupted

Striking & Finish

1. 18.

   Formwork struck at correct time / strength gain
   What to look forStrike permit issued referencing cube test or maturity meter result. Vertical formwork stripped first; soffit forms only after self-supporting strength. Backprops left in place per temporary works design.
   Acceptable whenVertical forms (walls, columns) typically strike at 8-24 hours when concrete reaches ≥ 5 N/mm². Soffit forms (slabs/beams) strike at 70% design strength minimum, typically 7-14 days. Per BS EN 13670 cl.5.6 and temporary works design.
   StandardBS EN 13670:2009 cl.5.6. Concrete Society CS141 — Formwork striking times. BS 5975:2019.
   Common defectsSoffit forms struck before 70% strength — excessive deflection or failureStrike time based on calendar age only, not strengthBackprops removed early to recycle props — slab cracksSharp edges and arrises damaged at strike — forms struck too lateNo strike permit issued — TWC sign-off missed
2. 19.

   Surface finish acceptable — no honeycombing or blowholes
   What to look forSurface inspected immediately after strike. No exposed aggregate or voids visible. Blowholes (air pockets) within accepted size and density. Colour even, no cement-fines staining or laitance separation.
   Acceptable whenNSCS finish classes: Class A (visual concrete) — blowholes < 10 mm dia, max 3% of surface area; Class B (basic finish) — blowholes < 15 mm; Class C (concealed) — minor honeycombing acceptable if structurally sound. No honeycombing exposing reinforcement.
   StandardNSCS Section 9 — Concrete surface finishes. Concrete Society Visual Concrete Code of Good Practice.
   Common defectsHoneycombing at base of pour — concrete dropped from height, segregatedBlowholes excessive — vibration insufficient, mix too stickyTide marks horizontal — pour stopped/restarted (cold joint)Form release agent staining — wrong product or excessSpalling on arrises at strike — concrete bonded to forms
3. 20.

   Dimensions and levels within tolerance

   Record: Deviation (mm)
   What to look forWall thickness measured at multiple points. Slab levels surveyed to grid. Column verticality checked at each lift. Setting-out preserved on element for follow-on trades.
   Acceptable whenPer BS EN 13670 Annex G / NSCS: column verticality ±h/300 or 15 mm (worse case); wall thickness ±10 mm; slab level ±15 mm to design; element overall length ±20 mm or L/600.
   StandardBS EN 13670:2009 Annex G — Geometrical tolerances. NSCS Section 9. BS 5606:1990 — Accuracy in building.
   Common defectsWall bowed mid-height — formwork insufficient walingsColumn out of plumb because formwork shifted during pourSlab level high — over-poured, not screeded backColumn undersized at top — formwork narrowed under hydrostatic pressure
4. 21.

   Any repairs carried out to approved method
   What to look forRepair method statement signed off by structural engineer. Repair extent agreed and recorded on drawings. Repair material data sheet on file — bond strength, modulus compatible with parent concrete. Repair re-inspected after curing.
   Acceptable whenRepairs per BS EN 1504-3 (structural repair) or 1504-4 (bonding). Material strength ≥ parent concrete. Bond to parent ≥ 1.5 N/mm² (pull-off test). Honeycombing exposing rebar = structural repair, requires engineer sign-off.
   StandardBS EN 1504 series — Products for repair of concrete structures. Concrete Society TR38 — Patch repair.
   Common defectsRepairs done with general mortar — no bond to parent, falls outCosmetic patching over honeycombing without exposing aggregate firstNo engineer sign-off on structural repairsRepair material colour-matched but cementitious incompatible (no SBR primer)Repairs not photographed before patching — no record of original defect

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