External Works · 7 checks

Groundworks & Earthworks
QA inspection checklist

Groundworks and earthworks quality audit.

Every check below carries what good looks like, when it passes, the standard it comes from and the defects that usually fail it. That guidance is what turns a tick-box into an inspection.

Excavation

  1. 1.
    Excavation to correct depth and formation
    Record: Depth (m)
    What to look forExcavation surveyed to correct depth and extent against design — checked with rotary laser or GPS rover at multiple points. Formation level free of soft spots, root pockets, and standing water. Sides battered or shored per excavation method statement and CDM 2015.
    Acceptable whenPer SHW Series 600 / BS 6031: formation level ±25 mm of design (typical highways tolerance), ±50 mm for general bulk earthworks. Stability per BS 6031 — 1:1 batter for cohesive, 1:1.5 for granular (rule of thumb, design overrides).
    StandardBS 6031:2009 — Code of practice for earthworks. Specification for Highway Works Series 600 (Earthworks). CDM Regulations 2015.
    Common defectsOver-excavated — design level missed, must be filled with engineered fillUnder-excavated — soft layer remains, settlement riskSides not battered or shored on > 1.2 m depth — collapse riskStanding water in excavation — formation softeningNo CAT-scan before dig — services struck
  2. 2.
    Formation level acceptable
    What to look forFormation walked / proof-rolled — no soft spots, springiness, or pumping. Surface free of vegetation, organic matter, and oversize material. Engineer / geotechnical sign-off on visible state. Photographic record before next layer placed.
    Acceptable whenPer SHW 600 / BS 6031: visual stability under loaded plant (no rutting > 25 mm under standard tipper); no pumping under proof roll; no spongy areas. Engineer's sign-off mandatory before any cover.
    StandardSHW Series 600. BS 6031:2009. SHW Series 700 (sub-base) clause 712.
    Common defectsSoft spot covered without remediation — settlement after constructionTrafficked formation by site plant — turned to mudVegetation tilled in — organic seam, future settlementNo engineer sign-off — disputes if failureFormation left exposed to rain too long — softening
  3. 3.
    CBR/plate bearing test results acceptable
    Record: CBR (%)
    What to look forIn-situ CBR (Dynamic Cone Penetrometer or DCP) or plate bearing test (BS 1377-9) at the frequency demanded by the spec — typically every 250-500 m² and at any suspect zone. Test against design value. Geotechnical engineer reviews and stamps result.
    Acceptable whenPer design: typical thresholds — formation under road sub-base CBR ≥ 5% for Type 1, ≥ 15% for thinner pavement designs. Plate bearing test K-value per design. Test frequency per SHW 600 / project Site Quality Plan.
    StandardBS 1377-9:1990 — In-situ tests. SHW Series 600. Design Manual for Roads and Bridges (DMRB) CD 225.
    Common defectsCBR < design — formation requires improvement (geogrid, lime stabilisation, or excavation)Test frequency too low — coverage gapsTests biased to easy locations — skewed resultPlate bearing made on softened surface after rainNo geotechnical sign-off

Fill & Compaction

  1. 4.
    Fill material matches specification
    What to look forFill material matches the SHW class declared in the spec (Class 1A general granular, Class 2 cohesive, Class 6F2/F3/F4/F5 selected granular/well-graded fill). Source declared on delivery note. Visual / sieve tests confirm grading and absence of contaminants.
    Acceptable whenPer SHW Series 600 Table 6/1 — material classification, suitability, plasticity index, moisture content range, and acceptable size limits per class. Imported fill: Material Quality Certificate from quarry. Site-won fill: classification report by competent geotechnical engineer.
    StandardSHW Series 600 — Earthworks. BS 6031:2009. BS 1377 — Methods of test for soils.
    Common defectsWrong class delivered — does not meet design strength after compactionOversize material in fill — voids around large stonesTopsoil / organic material mixed inSite-won fill not tested — properties unknownNo delivery records — traceability lost
  2. 5.
    Layer thickness correct
    Record: Layer (mm)
    What to look forFill placed in horizontal layers of compacted thickness per spec — typically 150-300 mm depending on material and compaction plant. Layer marked out with profile boards or laser. No "rolling thick lifts" — material brought up uniformly across area.
    Acceptable whenPer SHW Series 600 Table 6/4: maximum loose layer thickness depends on plant type and class — typically 150-225 mm compacted for vibratory roller, less for cohesive. Number of passes per Table 6/4 must be achieved.
    StandardSHW Series 600 Tables 6/1 and 6/4. BS 6031:2009.
    Common defectsLayer too thick — only top compacts, lower part looseNumber of passes not countedCompacted only along centreline — edges loosePlant too light for material — design density not achievedLayer placed unevenly — local thicknesses outside spec
  3. 6.
    Compaction test results acceptable
    Record: Dry density
    What to look forCompaction tested by sand replacement (BS 1377-9), nuclear density gauge, or air voids (cohesive). Result reported as % MDD or air voids. Frequency per SHW or method spec. Test at random locations and at suspect zones.
    Acceptable whenPer SHW 600 / project spec: granular fill ≥ 95% MDD (BS 1377 Test 12 — heavy hammer); cohesive < 5% air voids; some specs use Method spec (number of passes per layer per plant). Frequency typically 1 test per 500 m² per layer or 1 per 100 m of trench.
    StandardBS 1377-9:1990 — In-situ tests. BS 1377-4:1990 — Compaction tests. SHW Series 600 Table 6/4 (method spec) or 6/1 (end-product spec).
    Common defectsDensity below 95% MDD — fill behaves as loose soilCohesive air voids > 5% — settlement on saturationTest frequency too low — coverage gapsNuclear gauge not calibrated — invalid resultMethod spec used but pass count not recorded
  4. 7.
    Geotextile membrane installed where required
    What to look forGeotextile (separation, filtration, or reinforcement) per design — manufacturer and product code on roll label. Lapped per design — typically 300-500 mm minimum. Continuous across area, no tears or punctures. Edges well-anchored before fill placement.
    Acceptable whenPer BS EN 13249 / 13251 — geotextile to declared performance class. Lap ≥ 300 mm on weak ground; ≥ 500 mm on very weak. Reinforcement geogrid lapped per supplier (Tensar, Maccaferri) instruction with mechanical connectors as needed.
    StandardBS EN 13249:2016 — Geotextiles for use in roads. BS EN 13251:2016 — Geotextiles for earthworks. Highways England DMRB CD 225 / SHW 600.
    Common defectsLap too short — material works through gapGeotextile torn during fill placement — function lostWrong grade — non-woven instead of woven for reinforcementEdges not anchored — wind-blown / displaced before fillGeogrid laps not connected per spec — no reinforcement transfer

Questions people ask

What is a groundworks & earthworks QA inspection for?

To record that the work was checked against the specification before it was covered up or handed over: a pass or fail against each item, a measurement where one matters, and a photo where it failed. It is the evidence a client's quantity surveyor or clerk of works asks for, and the thing that settles the argument at final account.

What standards does this checklist check against?

Each item names its reference. On this checklist that includes BS 6031:2009, SHW Series 600. BS 6031:2009. SHW Series 700 (sub-base) clause 712., BS 1377-9:1990, SHW Series 600, SHW Series 600 Tables 6/1 and 6/4. BS 6031:2009., BS EN 13249:2016. The contract specification and the approved drawings always take precedence over a general standard; where they say something stricter, inspect to that.

Who signs a QA inspection off?

The person who carried out the check, named and dated, and where the contract calls for it the client's representative as a witness. The signature records that the check was done and what was found. It is not a warranty of the work.

How many items are on it, and do I have to use them all?

7 checks across 2 sections. Delete what does not apply to the job and add anything the specification asks for that is not here. A checklist that has plainly been thought about carries more weight than a long one nobody read.

Is this useful for a subcontractor as well as a main contractor?

More so. The subcontractor is the one who gets asked to come back and open something up. A signed inspection sheet with photos at the time is the cheapest insurance on a construction site.

Run this inspection on a phone

The same 7 checks, with the guidance a tap away, photos against each fail, measurements recorded, an NCR raised automatically and a branded PDF at the end. Signed on site. 14 days free.

Start free trial