— reviewed against the regs as they stand.
Quick answer: Every new dwelling built under Part L 2021 needs its own set of photographs, taken during construction, showing the insulation and airtightness were built properly. There are thirteen details across six categories: ground floor, walls, roof, openings, airtightness and building services. Each photo must be plot specific, carry the location, date and time, and be taken before the next trade covers the detail. The SAP assessor reviews them before signing the completion BREL report. A plot with gaps in its photographs can’t be signed off.
One page per plot. All thirteen details, when to catch each one, and the rules for every photograph. Print it and keep it in the site office. No sign-up.
Why the photographs exist
A SAP calculation is only as good as the building it describes. For years the as-built SAP assumed the insulation had gone in as drawn, because nobody could check once it was plastered over. The measured gap between designed and actual performance was large enough that the 2021 edition of Approved Document L added a paper trail. The builder photographs the details while they are visible, and the assessor checks them against the specification before signing that the dwelling was built as calculated.
The photographs sit alongside the rest of the completion package: the as-built SAP, the completion-stage BREL report (Building Regulations England Part L compliance report) signed by the assessor and the builder, the air test result and the EPC. The Part L guide covers how those fit together.
Who does what
- The builder takes them. There is no restriction on who holds the camera, but the site team is the only one there at the right moment.
- The SAP assessor reviews them against the specification the calculation used: insulation type and thickness, the junction details, the heating system and ventilation actually installed. Anything that doesn’t match gets raised before the as-built SAP is finalised.
- Building Control receives them with the completion BREL report.
The review is part of the job, not an extra. Our new-build SAP includes it as standard.
The thirteen details
The requirement is organised in six categories. Walls, roofs and openings are per type, so a house with a brick-and-block main wall and a timber-framed dormer needs the wall details for both.
| Ref | Detail | The photograph must show | Catch it before |
|---|---|---|---|
| 1a | Ground floor insulation | Boards laid tight with closed joints, and the thickness | the screed or deck goes down |
| 1b | Perimeter edge insulation | The upstand at the slab edge, continuous all round | the screed goes down |
| 1c | External door thresholds | Insulation under and around the threshold, below the DPC | the frame and screed go in |
| 2a | Wall / ground floor junction | Wall insulation starting low enough to overlap the floor insulation | the floor is finished |
| 2b | Wall insulation and penetrations | Batts or boards tight, no gaps or mortar snots, penetrations sealed | the outer leaf or boarding closes it |
| 3a | Roof insulation at joist level | Both layers, cross-laid, carried into the eaves without compressing | the loft is boarded or handed over |
| 3b | Roof insulation at rafter level | Between and over the rafters; continuity at gables and verges | the plasterboard goes up |
| 4a | Window position | Frame in line with the insulation or cavity closer; jambs, sill and head | the reveals are plastered |
| 4b | Door position | Frame in line with the insulation or cavity closer | the reveals are plastered |
| 5 | Airtightness details | Sealing of service penetrations, membrane laps, tapes at frames | dry-lining and boxing-in |
| 6a | Building services: plant | Legible data labels on the boiler or heat pump, cylinder and controls | handover |
| 6b | Building services: pipework | Primary pipework insulated, including runs in voids, and the cylinder | floors and ceilings are closed |
| 6c | Ventilation and renewables | Extract fans, the MVHR unit and insulated ducting, PV or solar thermal | the ceilings close |
Not every plot has every detail. A cold-roof bungalow has no rafter-level insulation, and a flat on the second floor has no ground floor. Mark those as not applicable rather than leaving them blank, so the assessor can see the gap is deliberate.
Most of the thirteen are the junctions, where one element meets another. That’s where insulation most often stops short, and those junctions are exactly what the psi-values in your SAP assume are continuous. A photograph of a wall that stops 50 mm short of the floor insulation shows a thermal bridge the calculation has been told doesn’t exist.
What makes a photograph acceptable
It belongs to this plot. Every dwelling needs its own set, even on a terrace of identical houses. Photographs cannot be shared or reused between plots.
It records where and when. Turn on location services for the camera and check that the date and time are right before the first photo. Those details tie the photo to a particular plot on a particular day, and they are the first thing checked when a set looks too tidy.
It is named so someone else can find it. Put the plot and the detail reference in the file name, for example Plot07_2b_rear.jpg. A folder of 400 files called IMG_4471.jpg has to be sorted by hand at the end, which is when the gaps are found.
It shows the whole detail and the close-up. A wide shot shows where on the building you are. A close-up shows the joint, the lap or the closer. One photo rarely does both, so take two.
It shows thickness where thickness matters. A tape measure against the insulation answers the assessor’s first question without a phone call.
It is in focus and lit. Inside a dark cavity or a loft, use the flash. Blurred or dark photos get sent back.
When on the programme to take them
The table above gives the latest moment for each detail. In programme order it runs like this:
- Groundworks and slab: 1a, 1b, 1c. Photograph once the insulation is down, before the screed or deck.
- Superstructure: 2a, 2b, lift by lift for a masonry cavity, or before the sheathing and cladding go on for timber frame.
- Roof: 3b before the plasterboard. 3a once the second layer is down in the loft.
- First fix: 4a, 4b and 5 as the frames go in and the penetrations are sealed, before dry-lining.
- Services: 6b before floors and ceilings close, then 6a and 6c at second fix and commissioning.
Brief each trade at the start of its package, not at the end. The groundworker who leaves the slab on a Friday is the only person who can photograph 1a, and nobody will ask them to on Monday.
The failures we see
- One plot photographed for the whole site. That’s the most common gap, and there’s no fixing it after completion.
- The detail is already covered. The insulation photo taken after the first sheet of plasterboard went on.
- No context. A close-up of a board edge that could be anywhere on any plot.
- Missing types. The main wall is photographed but the dormer, bay or rear extension wall is not.
- Services left to the end. Pipework in the floor void gets boarded over during second fix, before anyone thinks of it.
- Mismatch with the SAP. The photos show 90 mm of insulation where the SAP assumed 100 mm, or a different window frame. The photos do their job and the as-built SAP has to be re-run.
The last one isn’t a photography problem, and it’s the best reason to send photos to the assessor as you go. A mismatch found at first fix is a conversation. Found at completion, it’s a failed as-built.
If you get to the end with gaps
The assessor can’t sign the completion BREL report for a plot without its evidence. Without the as-built SAP and the EPC, Building Control can’t issue the completion certificate. From there the choices are opening up enough of the construction to photograph it, or asking Building Control whether it will accept something else, such as delivery notes, a clerk of works’ records or another inspection. That is Building Control’s decision, and not one to plan around.
Which edition applies
This guide describes Approved Document L 2021, which applies to new dwellings in England today. The Future Homes Standard edition takes effect for new schemes from 24 March 2027, with transitional arrangements for projects already under way. The Future Homes Standard guide has the dates. Check the edition your plots are being built under with your assessor, and we’ll update this page if the requirement changes.
The bottom line
The photographs are cheap to take and very expensive to be without. Print the checklist, brief every trade, name the files by plot and detail, and send them to your assessor as each stage closes. If you’d like one firm to run the SAP, check the photographs and sign off the BREL, send us the drawings. Our New Build Compliance Pack also covers the air tests, water calculation and EPCs.
Common questions
What photographic evidence does Part L require?
Under Approved Document L 2021, every new dwelling needs photographs showing the insulation and airtightness details were built continuously and properly, across six categories: foundations and ground floor, each external wall type, each roof type, each opening type, the airtightness details, and the building services. That comes to thirteen individual details for a typical house. The photographs are reviewed by the SAP assessor before the completion BREL report is signed, and go to Building Control with it.
Who has to take the Part L photographs?
Anyone can — there is no qualification attached. In practice it is the builder or site manager, because they are on site at the moment each detail is visible. The SAP assessor does not normally take them; the assessor reviews them against the specification the calculation was based on.
Can I use the same photographs for identical plots?
No. The evidence is plot specific: every dwelling needs its own set, even on a row of identical houses. That is why the location and date stamp matter — they tie each photograph to a particular plot on a particular day.
What happens if the photographs are missing?
The assessor cannot sign the completion BREL report for that plot, and without the as-built SAP and EPC Building Control cannot issue the completion certificate. The options at that point are poor: opening up the construction so it can be photographed, or asking Building Control whether it will accept alternative evidence, which is its decision to make and not something to count on.
Do I need a special app for Part L photographs?
No. A phone camera with location services switched on records the date, time and position, which is what is needed. Several site apps organise the photos by plot and detail and produce a report, and they suit larger sites. What matters either way is that every detail is covered, for every plot, before it is hidden.
Does photographic evidence apply to extensions and conversions?
No. Approved Document L applies the photographic evidence requirement to new dwellings. Extensions, conversions and work to existing homes are assessed differently and do not need the BREL report or the photographs, though Building Control can still ask to see work before it is covered.