NHBC Chapter 9.1–9.4 · 23 checks · proplot.co.uk
The plot outside the front door — levels and falls, DPC clearance, drives and paths, thresholds, drainage covers, boundaries, landscaping and meter boxes.
23 checks · Reviewed by the ProPlot site team · How we write these guides
In short
The external works inspection covers everything outside the shell before handover. The inspector checks finished ground levels and DPC clearance, falls away from the building, drives, paths and paving, drainage covers and gullies, retaining structures, boundary treatments, and that air bricks and vents are clear and unobstructed.
External works are the last thing built and the first thing the buyer sees, which is a bad combination for quality. They are also where two earlier stages get quietly undone: ground levels raised during landscaping can bury a DPC that was correct when it was laid, and a drive laid to the wrong fall can send surface water back at a threshold that passed inspection months earlier.
The inspector checks levels and falls first — away from the building everywhere, with at least 150mm of masonry above finished ground level, and no landscaping bridging the DPC. Then the surfaces: sub-base and construction depth for drives, edge restraint, jointing, lippage and trip hazards on paths, and the transition at accessible thresholds where a drainage channel usually does the work. Drainage covers should sit flush and at the right duty for whatever runs over them.
Finally the plot-level items that generate handover complaints: boundary fences and walls plumb and to the right heights, gates operating, topsoil depth and turf laid to falls, meter boxes and external lighting complete, and everything clean and safe for a family to walk into. Clear this list before the pre-CML visit and that inspection becomes much shorter.
When it happens
Once the plot is released from construction traffic and surfaces are laid — before the pre-CML visit, because incomplete externals are one of the most common reasons a CML inspection is aborted.
Who inspects
Warranty provider inspector at the pre-CML visit, the adopting authority for any roads and sewers being offered for adoption, and the buyer at handover.
If it fails
Level and fall problems mean lifting and re-laying finished surfaces. Buried DPCs are a warranty issue that can require excavating a perimeter trench around a completed home.
Concealed work cannot be re-photographed later. Take these before the element is covered and file them against the plot.
A Reportable Item (RI) is a defect the inspector records against the plot. NHBC weigh each one by its Damage Potential, and the score feeds your site's Construction Quality Review. These are the ones raised most often here:
The measurable values most often argued about at the external works & pre-handover visit, each traced to an openly published source. Take a tape to the ones that apply before you book.
| What | Value | Type |
|---|---|---|
| Accessible threshold upstandPrincipal entrance to a dwelling designed to be accessibleMeasure from the finished external surface to the top of the threshold after paving is laid, not from the DPC. | 15 mm maximum total upstand, chamfered or pencil-rounded above 5 mm | Maximum |
| Additional flue terminal separation rulesBeyond standard table distances, all flue terminals must maintain a minimum 300mm clearance from any combustible material, such as window framesConfirm all terminals are at least 300mm from combustible window frames, and verify heat shield dimensions if present. | 300 mm | Minimum |
| Handrails for external stepsA handrail is required for external flights of steps when the total rise exceeds 600mm and the individual step going is less than 600mmCheck that a handrail is fitted to external steps where the total rise is over 600mm, ensuring it is secure and at an appropriate height. | 600 mm | Exact |
| Landscaping Levels and DPCExternal ground levels, including landscaping finishes such as turf, must be maintained at a minimum of 150mm below the damp proof course (DPC) levelCheck that all finished landscaping levels are at least 150mm below the DPC. | 150 mm | Minimum |
| Specific guarding requirements for level changesGuarding is mandated for retaining structures where the drop is greater than 600mm to an accessible lower levelMeasure the height of level changes and ensure guarding is correctly installed to a minimum height of 1100mm, with no climbable features. | 600 mm | Minimum |
| Water efficiency limit for a new dwellingNew dwelling water efficiency calculationCheck the fittings actually installed against the schedule used in the calculation — a changed shower head can break the figure. | 125 litres per person per day (110 where the tighter optional requirement is imposed by condition) | Maximum |
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Confirm at least 150mm of masonry remains above finished ground level all round (AD C)
AD CCheck ground falls away from the building on every elevation (NHBC 9.1)
NHBC 9.1Verify no landscaping, decking or planting bridges the DPC (AD C)
AD CConfirm air bricks and subfloor ventilators are clear and above finished level (AD C)
AD CCheck sub-base type and depth match the specification for the surface and its use (NHBC 9.1)
NHBC 9.1Verify edge restraints are installed and haunched before surfacing (NHBC 9.1)
NHBC 9.1Confirm falls direct surface water to a gully or permeable area, not towards the house (AD H3)
AD H3Check paths are free of trip hazards, with lippage and joint widths within tolerance (NHBC 9.1)
NHBC 9.1Verify accessible thresholds have the correct drainage channel and level transition (AD M)
AD MConfirm steps and ramps have compliant rise, going, handrails and slip resistance (AD K)
AD KCheck all chamber covers sit flush, are the correct duty and are marked as foul or surface (BS EN 124)
BS EN 124Confirm gullies are clear, trapped and set to the finished surface level (AD H1)
AD H1Verify soakaways and permeable areas are complete and not clogged with construction fines (AD H3)
AD H3Check meter boxes, external taps and EV charge points are fitted, sealed and operational (NHBC 9.1)
NHBC 9.1Confirm external lighting is installed, aimed and working (BS 7671)
BS 7671Verify fence and wall positions match the plot layout and title plan (NHBC 9.2)
NHBC 9.2Check fence posts are set to the correct depth, plumb and securely concreted (NHBC 9.2)
NHBC 9.2Confirm retaining structures over 600mm have a design and adequate drainage (NHBC 9.2)
NHBC 9.2Check topsoil depth, grading and turf or seeding match the landscaping specification (NHBC 9.3)
NHBC 9.3Verify gates, bin stores and cycle stores are complete and operate correctly (NHBC 9.2)
NHBC 9.2Confirm the plot is clean, with all construction materials, spoil and debris removed (NHBC 9.4)
NHBC 9.4Check external decoration, render and cill finishes are complete and undamaged (NHBC 6.11)
NHBC 6.11Verify safe, complete pedestrian access from the road to the front door (CDM 2015)
CDM 2015Externals are what the customer sees first and what site traffic damages last. Sequencing and protection are the whole game. No inspector will fail the visit on these — they are the difference between a plot that passes and a plot that hands over clean.
Protect finished paving, kerbs and driveways from plant and deliveries
Tracked plant on new block paving cracks and rotates blocks, and the repair never matches.
When: From the moment an area is laid.
Keep gullies, channels and drainage covers covered until the final clean
Silt and mortar washings in a new gully means lifting the finished surface to clear it.
When: Through the whole externals phase.
Protect thresholds, door frames and cills during hard landscaping
Barrow handles and slab edges destroy new frames, and a replaced frame means new mastic, new decoration and a re-inspection.
When: Before landscaping starts.
Photograph levels, falls and drainage runs before the final surface
Standing water is the number one external callback and it is far cheaper to prove the fall before you close it up.
When: At sub-base stage.
Keep the plot frontage presented from the point the scaffold comes down
A tidy frontage is how the site is judged by inspectors, customers and the sales team, and it changes the tone of every visit.
When: Continuously from scaffold-down.
Set turf and planting to the right level against the DPC
Soil bridging the DPC is a damp bridge and it is a certain warranty item, but it is also very easily done by a landscaper working to a visual line.
When: At topsoil and turfing.
11 inspection points that apply at the external works & pre-handover stage, each written in our own words from openly published guidance, with how to check it on site and what counts as acceptable. Use the checklist above on the day and this register when you need to settle a detail.
Levels raised over the DPC
Landscaping tips soil against the wall and the 150mm clearance disappears. Set a permanent mark at DPC level on each plot and check against it after grading.
High — a bridged DPC is a damp claim waiting to happen.
Drive falling towards the house
Water is directed at the threshold instead of the gully. Set falls with a level before the surfacing crew arrives, not after.
Medium to high — Part M non-compliance blocks completion.
Chamber covers left proud
Frames set to the pre-surfacing level become trip hazards. Adjust frames when the finished level is confirmed.
Medium — but often means relaying finished paving.
Sub-base skimped under a drive
Rutting and settlement appear within the first year and the whole drive comes up. Check depth and compaction while it is open.
Medium — usually cleared quickly if spotted before the visit.
ProPlot's audit tool includes these external works & pre-handover checks as interactive helpers — tick items off, attach GPS-stamped photos, and share the report with your inspector in one tap. Free while in beta.
The key stage inspection sequence on a typical UK housing plot.
Excavation & foundations
21 checks →
Drainage
20 checks →
Basement / lower ground
28 checks →
Ground Floor & Slab
19 checks →
Superstructure
22 checks →
Timber Frame Erection
21 checks →
Roof
22 checks →
Windows and External Doors
24 checks →
Insulation & Airtightness
23 checks →
First Fix
28 checks →
Fire Stopping
22 checks →
Pre-Plaster
21 checks →
Second Fix
31 checks →
Pre-handover
22 checks →
General Quality
20 checks →
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