What is Appendix B?

The part of SAP that lists exactly which photos you need for Part L

Appendix B is the section of the UK SAP methodology 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 sections that match the construction sequence. Different assessors and accreditation bodies group them slightly differently, but the sections you'll typically photograph are:

  1. Foundations, DPC and ground-floor insulation - before the slab or suspended floor goes in
  2. External walls and cavity-wall insulation - while the cavities are still open
  3. Floor and floor insulation - before the screed or final flooring
  4. Roof and loft insulation - before the final ceiling or roof covering closes it up
  5. Windows, doors and glazing - showing installation and sealing
  6. Airtightness measures - membranes, tapes, and sealed service penetrations
  7. Heating, hot water and ventilation systems - plant installation and commissioning
  8. Renewable and low-carbon technologies - solar PV, heat pumps, and the like

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.

Buildsnpper handles the metadata bit automatically - GPS, date, and timestamp on every photo. Section-by-section capture means nothing gets filed wrong. One-tap report, 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 is part of SAP, which is 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 the UK SAP methodology that specifies the photographic evidence required to demonstrate a new-build dwelling was constructed to the design. It covers foundations, walls, floors, roof, glazing, airtightness, heating, and renewables.

What photos are required for Part L Appendix B?

At a minimum, clear photos of each construction stage that gets covered up: foundations and DPC, cavity-wall insulation, floor insulation, roof and loft insulation, windows and glazing, airtightness measures, heating and ventilation plant, and any low-carbon technologies. 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 Buildsnpper removes the risk of missing metadata or mis-filing.

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