NHBC Chapter 1.4 (final certificate / CML release) · 22 checks · proplot.co.uk
The final NHBC key stage — also called the pre-CML visit. Finishes, commissioning certificates, EPC, external works and close-out of every earlier Reportable Item.
22 checks · Reviewed by the ProPlot site team · How we write these guides
In short
The pre-handover inspection (still widely called pre-CML) is the last NHBC key stage before the final certificate and the lender's Cover Note. The inspector checks the dwelling is complete and weathertight, that heating, ventilation and electrical commissioning certificates are on the plot file, that the EPC and Part L paperwork is filed, and that every earlier Reportable Item is closed out with evidence.
The pre-CML visit decides whether the plot can be sold. Without the Cover Note the buyer's lender will not release funds, so this inspection sits directly on the critical path of your cash flow — a failure does not just cost a re-visit, it moves a legal completion date.
By this point the inspector is checking two things. First, that every Reportable Item from the earlier key stages has actually been closed out, with evidence. Second, that the house is genuinely finished: services commissioned and certificated, appliances working, external works complete enough for safe access, and nothing outstanding that a purchaser would reasonably reject.
The paperwork matters as much as the building. Gas, electrical, ventilation and heating commissioning certificates, the EPC, fire alarm test records and any structural or drainage sign-offs need to be on the plot file and available. The most common reason a CML visit is abortive is not a defect at all — it is missing documents or an unfinished path to the front door.
When it happens
When the plot is complete, commissioned and clean, before legal completion. Allow at least a week between booking and the intended completion date so there is time to clear anything raised.
Who inspects
Warranty provider inspector for the Cover Note / CML, and building control for the completion certificate. They are separate documents and both are needed.
If it fails
No CML means no mortgage drawdown. Sales slip, buyers get nervous, and re-inspections queue behind everyone else on the patch. Every item on this list is cheaper to clear before the visit than after.
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 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 |
| Appliance space, general storage, and unit installationDesign specifications should account for standard appliance depths, typically 600mm, even if appliances are not suppliedConfirm correct allowances for appliance spaces, general storage provisions are adequate, and all units and shelving are level, secure, and installed per manufacturer instructions. | 600 mm | Exact |
| Carbon monoxide alarm positionRoom containing a fixed combustion applianceConfirm the alarm position against the appliance location at handover, and check it has not been moved to suit decoration. | Ceiling mounted at least 300 mm from any wall and 1–3 m horizontally from the appliance, or wall mounted above the height of any door or window and at least 150 mm from the ceiling | Minimum |
| Cistern access requirementsAdequate access must be provided to cold water storage cisterns located in roof spaces and voids, through an opening of at least 520mm in each directionEnsure access hatches meet size requirements and that a safe, stable platform is present for maintenance of the cistern. | 520 mm | Minimum |
| Clear opening of an escape windowFirst floor and loft rooms served by an escape windowMeasure the clear opening with the sash fully open — restrictors, frames and opening gear all reduce it. Check the cill height against finished floor level, not screed level. | 0.33 m² clear openable area, at least 450 mm in both height and width, with the bottom of the opening 800–1100 mm above floor level | Minimum |
| Clear opening width of an internal doorInternal doorway on the entrance storey of a dwellingMeasure the clear opening with the door at 90°, from the face of the door to the opposite stop — not the structural opening. | 750 mm from a corridor at least 900 mm wide; 775 mm from a 825 mm corridor; 900 mm from a 750 mm corridor | Minimum |
| Conditions for Pipe Freezing CalculationsCalculations for pipe insulation to prevent freezing are based on specific assumed conditions, typically including an external air temperature of -6°C and an internal water temperature of +7°C | 6 °C | Exact |
| Critical locations for safety glazingInternal and external glazing in a dwellingCheck the kitemark or safety mark on each pane in the critical zones at handover, including glazed side panels and low-level windows. | Below 800 mm from floor level in walls and partitions; below 1500 mm in doors and in side panels within 300 mm of a door edge | Maximum |
| Door Clearances and Fire Door InstallationInternal doors, including fire doors, must be installed with sufficient clearance from the finished floor level to accommodate flooring, typically around 10mm for non-fire doorsCheck that door clearances are adequate for floor coverings and fire door gaps are within specified tolerances and installed correctly. | 10 mm | Exact |
| Electrical Accessory Clearance Elevation DetailElevation diagrams specify the minimum 300mm horizontal separation required between electrical accessories and the edges of sinks or wash basinsVerify, using a tape measure, that electrical accessories maintain the specified horizontal clearance from wet areas. | 300 mm | Minimum |
| Electrical Accessory Clearance from Water DiagramsDiagrams illustrating the required 300mm minimum horizontal clearance for electrical accessories from water sources, such as sinks and wash basins, are commonly used in guidance documentsRefer to relevant diagrams to confirm correct clearances during electrical rough-in and final fix. | 300 mm | Minimum |
| Flue pipe horizontal run limitA short horizontal section, typically up to 150mm in length, is permitted within a flue pipe system to connect a back-outlet liquid fuel appliance to the main flue, provided the primary run remains as vertical as possible.N/A | 150 mm | Maximum |
| Going of a tapered treadWinder or tapered tread in a private stairMeasure the going on the centre line for flights under 1 m wide, and check the narrow end of every winder rather than sampling one. | Measured at the centre of the flight; at least 50 mm at the narrow end | Minimum |
| Guarding height in a dwellingSingle-family dwellingMeasure from the pitch line on flights and from finished floor level elsewhere. Check a 100 mm sphere cannot pass through any opening in the guarding. | 900 mm to stair flights; 1100 mm to landings, balconies and external edges | Minimum |
| Handrail height on a stair or rampPrivate stair, landing or ramp in a dwellingCheck the height at the top and bottom of every flight — a bracket set out from the string can put the mid-flight height outside the range. | 900–1000 mm above the pitch line or floor | Range |
| 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 |
| Handrails for Tapered Treads and WindersFor stairs incorporating tapered treads or winders, any handrail provided on the outside of the turn must offer a safe handhold for the full rise of the stair, particularly if the total rise exceeds 600mmVerify that a safe handhold is available throughout the entire rise of tapered stair sections, whether by handrail or suitably designed newel. | 600 mm | Maximum |
| Hearth Provision and Floor FinishesA hearth may not be necessary if an appliance's flame or incandescent material is positioned at least 225mm above the floorConfirm that gas appliance hearths have clear edge markings or a change in level to indicate the safe zone for floor finishes, or that no hearth is needed if the appliance height allows. | 225 mm | Minimum |
| Hearth Thickness for AppliancesHearths for appliances, other than specific solid fuel or gas-specific cases, must be constructed from non-combustible materials with a minimum thickness of 12mm.Check that all appliance hearths meet the minimum 12mm thickness requirement and are made of non-combustible material. | 12 mm | Minimum |
| Intermittent extract rates by roomIntermittent mechanical extract in a wet roomMeasure with an anemometer at the terminal, not the fan, and record the reading per room for the commissioning sheet. | Kitchen 30 l/s next to the hob or 60 l/s elsewhere; utility room 30 l/s; bathroom 15 l/s; WC 6 l/s | Minimum |
| Landing length at the top and bottom of a flightLanding at the head or foot of a private stairCheck the door swing on plan and again on site — a door opening onto the landing must not reduce the clear length. | At least equal to the least width of the flight, kept clear of door swings | Minimum |
| 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 |
| Maximum gap in guardingGuarding to a stair, landing, balcony or floor edge in a dwellingTest with a 100 mm gauge at the widest point of every bay, including the triangular gap at the bottom of a flight and between the string and the first baluster. | No opening should allow a 100 mm sphere to pass | Maximum |
| Maximum hot water temperature at a bathHot water supply to a fixed bath in a dwellingRun the bath tap to full temperature and measure at the outlet during commissioning; record the reading against the plot. | 48 °C | Maximum |
| Private stair rise, going and pitchPrivate stair within a single dwellingMeasure the first and last rise as built — floor finishes added later are the usual cause of an unequal step. | Rise 155–220 mm, going at least 220 mm, maximum pitch 42°, and twice the rise plus the going between 550 mm and 700 mmTolerance: All rises in a flight must be equal | Range |
| Purge ventilation opening areaHabitable room ventilated by openable windowsWork the openable area out per room from the window schedule at design stage, then confirm the opening angle achieved on site. | One twentieth (1/20) of the floor area of the room for a hinged or pivot window opening 30° or more | Minimum |
| Soundproofing Measures for Soil PipesSound insulation for soil pipes involves either encasing them in boxing made from a material with a minimum mass of 15kg/m², or wrapping them with at least 25mm of unfaced mineral wool, typically 10kg/m³ densityCheck that soil pipes are either properly wrapped with mineral wool or housed in a suitably mass-dense, insulated boxing. | 25 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 |
| Stair Handrail Height and ClearanceA handrail is mandatory for flights of stairs where the rise exceeds 600mmCheck the handrail height, continuous grip, 25mm clearance, and ensure ends are safely terminated. | 600 mm | Minimum |
| Staircase guarding requirementsStaircases and landings require adequate guarding where there is a drop of more than 600mmVerify that guarding is present where required, continuous, securely fixed, at the correct height, and prevents a 100mm sphere from passing through any gap. | 600 mm | Exact |
| Tread overlap for open-riser stairsFor stairs with open risers, each tread must overlap the one below by a minimum of 16mm, or 15mm in Scotland, to meet safety requirements and prevent foot entrapment.Visually check and measure the overlap of treads in open-riser stairs to confirm it meets the minimum specified distance. | 16 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 |
| Water seal depth at appliance trapsAppliance trap on a branch discharge pipeTest at second fix by filling and discharging each appliance, then checking the seal has not been drawn out by the run. | 75 mm for baths, basins, sinks and showers on a branch; 50 mm for a WC trap | Minimum |
0 of 22 ticked — saved on this device
Check all snagging items from previous NHBC inspections are resolved and signed off (NHBC 1.4)
NHBC 1.4Check all party wall / sound insulation details are complete and match Robust Details or approved plan (AD E)
AD ECheck loft insulation coverage matches specification with no displaced or missing areas (AD L1A)
AD L1AVerify all internal decoration is complete, consistent and to acceptable finish standard (NHBC 9.4)
NHBC 9.4Inspect all flooring for damage, gaps, lippage and check thresholds / transitions are secure (NHBC 8.3)
NHBC 8.3Check kitchen units, worktops, splashbacks and appliances are installed and operational (NHBC 8.3)
NHBC 8.3Confirm all sanitary ware is fitted, sealed and operational (taps, WCs, showers, baths) (NHBC 8.1)
NHBC 8.1Verify all mastic / sealant joints are complete around baths, showers, worktops and externally (NHBC 8.3)
NHBC 8.3Confirm all ironmongery is fitted — door closers, latches, letterboxes, house numbers (NHBC 8.2)
NHBC 8.2Check all windows and doors operate freely with locks, handles and restrictors functional (AD Q)
AD QCheck meter boxes fitted, connections live and all service supplies commissioned (NHBC 8.1)
NHBC 8.1Confirm fire detection system tested, commissioned and certificate available on site (BS 5839-6)
BS 5839-6Verify boiler / heating system has been commissioned with certificate and user guide provided (AD L1A)
AD L1AConfirm all gas, electric and water installations have valid commissioning certificates (BS 7671)
BS 7671Verify Part P electrical certificate and any Gas Safe certificates are available on site (AD P)
AD PConfirm ventilation system commissioned and airflow rates recorded per dwelling (AD F)
AD FVerify all external works complete — paths, drives, fencing, turfing / seeding, meter boxes (NHBC 9.1)
NHBC 9.1Check external drainage gullies are clear, covers sit flush and surface water drains freely (AD H)
AD HConfirm any communal areas (apartments) are complete — lighting, fire doors, signage (AD B)
AD BVerify EPC certificate has been issued and rating matches SAP calculation (AD L1A)
AD L1AConfirm the as-built BREL report and photographic evidence are complete for the plot (BREL)
BRELConfirm property is clean, safe and ready for handover — all builder debris removed (NHBC 1.4)
NHBC 1.4Passing the visit and handing over a plot the customer is delighted with are two different standards. This is the second one. No inspector will fail the visit on these — they are the difference between a plot that passes and a plot that hands over clean.
Keep hard floor protection and stair covers on until the final clean
Every trade after the floor is laid is a scratch risk, and a replaced floor at this stage delays the legal completion.
When: From floor covering to the day before handover.
Protect ironmongery, sanitaryware and worktops
These are the items customers inspect closest and the ones with the longest replacement lead times.
When: On installation.
Label the consumer unit, stopcock, isolation valves and stop valves clearly
A labelled plot is a plot the customer can manage themselves, and it removes a whole category of first-year callbacks.
When: At commissioning.
Commission everything and leave the paperwork in one place for the customer
Heating, ventilation, alarms, appliances. The demonstration at handover goes far better when the file is already assembled.
When: Before the pre-handover visit.
Walk the plot at customer eye level, with the lights on and the curtains open
Inspectors look for compliance. Customers see paint runs, mastic lines and door gaps. Walk it the way they will.
When: Two weeks before handover, then again the day before.
Run every tap, flush every WC and open every window and door
Airlocks, stiff hinges and misaligned catches are all five-minute fixes now and a service visit later.
When: Final walk.
Photograph the finished plot on the day of handover
A dated record of condition ends most damage disputes in the first weeks of occupation.
When: Handover day.
3 inspection points that apply at the 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.
Paperwork not on the plot file
The systems are commissioned but the certificates are in someone's van or inbox. Collect them as each trade finishes, not on the morning of the visit.
High operationally — an abortive visit moves a legal completion date.
External works unfinished
A safe, complete route to the front door and functioning surface drainage are conditions, not nice-to-haves. Muddy plot access aborts CML visits routinely.
High — the inspector will not release with unsafe access.
Previous RIs closed without evidence
If the item was concealed work, you need the photograph. Close out each RI with a dated image at the time you fix it.
High — concealed work cannot be re-photographed after the event.
Ventilation airflow rates never measured
Commissioning of the ventilation system is a Part F requirement with recorded figures per room. Book the commissioning engineer in advance of the visit.
Medium — but it delays the certificate all the same.
ProPlot's audit tool includes these 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 →
External Works & Pre-Handover
23 checks →
General Quality
20 checks →
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