What is Appendix B?

The part of Approved Document L (Volume 1) that lists exactly which photos you need for Part L

Appendix B is the section of Approved Document L (Volume 1) that sets out the photographic evidence required to show a new-build dwelling was actually built to the design. Builders capture photos as construction progresses; the OCDEA assessor reviews them before signing off the BREL report.

In other words: it's the bit of the regulations that turns "we built it right, honest" into "here's the photographic proof, section by section, with GPS and timestamps." It exists because what's hidden inside a wall can't be checked once the plasterboard's on.

What Appendix B covers

Appendix B splits the evidence into six numbered groups, and these are the sections you'll photograph:

  1. Foundations and ground floor - edge insulation, the door threshold and below the DPC, before the slab or suspended floor covers it
  2. External walls - the ground floor to wall junction and anything structural that passes through the insulation, while the cavities are still open
  3. Roof - insulation at joist or rafter level and at the eaves and gables, before the final ceiling or roof covering closes it up
  4. Openings - windows and doors sitting in line with the cavity closer or insulation line
  5. Airtightness - membranes, tapes, and sealed service penetrations, where the insulation photos don't already show them
  6. Building services - heating, hot water, ventilation and low-carbon plant: the make, model and serial number, plus insulated pipework and ductwork

For each section, the assessor will expect at least one photo per plot showing the construction clearly, with the metadata to prove when and where it was taken.

What makes a photo count as valid Appendix B evidence

  • Clear subject. Sharp focus, decent light, the construction feature centred. A blurry wide shot won't do.
  • GPS coordinates embedded. The metadata proves the photo was taken on the actual plot.
  • Date and timestamp. Proves the photo was taken at the relevant construction stage, not reconstructed from a phone gallery six months later.
  • Linked to the correct plot. Multiple plots on one site means keeping photos separated properly. This is where zip files of un-named JPEGs fall over.
  • Filed against the correct section. Photo of a DPC filed under "roof insulation" creates a headache for the assessor and delays sign-off.

Buildsnapper handles the metadata bit automatically - GPS, date, and timestamp on every photo. Section-by-section capture means nothing gets filed wrong. Make the report in one tap, then send it straight to your assessor. From £6.67 per month, 14-day free trial. See how it works.

Common Appendix B mistakes

  • Photos taken without location services on. No GPS on the photo means the assessor can't verify where it came from. If location was off at the time, you can't add GPS after the fact.
  • Photos imported from the phone gallery. These often lose metadata in transit, and the timestamps may not match the actual construction stage.
  • Missing stages. Missing a single section - say, the cavity-wall insulation before it was closed up - can mean opening the wall back up. Or a delay while the assessor decides what evidence they can accept instead.
  • Multiple plots mixed together. One zip with 300 photos across five plots. The assessor has to sort it. They charge for the time.
  • No link between the photo and the construction stage. A photo with no context is just a photo. The assessor needs to know what they're looking at.

How Appendix B connects to the rest of Part L

Appendix B sits in Approved Document L (Volume 1), alongside SAP, the calculation methodology. SAP predicts how the building will perform from the design; Appendix B is how you prove the building was actually constructed to match. Together they feed into the BREL report that the OCDEA produces to sign off Part L compliance for new dwellings.

Under the Future Homes Standard, the expectations on Appendix B photographic evidence get tighter. More focus on the Performance Gap means more scrutiny of whether the as-built matches the design. Which means more photos, better organised, or more delays at handover.

Frequently asked questions

What is Appendix B?

Appendix B is the section of Approved Document L (Volume 1) that specifies the photographic evidence required to demonstrate a new-build dwelling was constructed to the design. It covers six groups: foundations and ground floor, external walls, roof, openings, airtightness, and building services.

What photos are required for Part L Appendix B?

At a minimum, clear photos of each of the six groups before the work gets covered up: foundations and ground floor, external walls, roof, openings, airtightness, and building services such as heating, ventilation and low-carbon plant. Each photo needs GPS, a date, and a timestamp.

Do Appendix B photos need GPS and timestamps?

Yes. Without GPS coordinates and a verified date and time, the assessor can't confirm the photo was taken on the correct plot at the correct construction stage. Photos taken with location services switched off can't have GPS added after the fact.

How many photos per plot do I need?

At least one clear photo per Appendix B section per plot. In practice most builders capture several per section to give the assessor options. Your OCDEA will tell you if more are needed.

What happens if an Appendix B photo is missing?

The assessor flags it. You either supply an equivalent photo taken at the time, open the work back up to photograph the missing section, or accept a delay while the assessor decides what alternative evidence they can accept. None of the options are cheap.

Can I use photos taken on a regular phone?

Yes, if location services are on so the photos are GPS-tagged, and you organise them by plot and section. In practice, a purpose-built evidence app like Buildsnapper removes the risk of missing metadata or mis-filing.

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