At handover you should receive a Building Regulations completion certificate, any competent person scheme certificates (electrical, gas, windows), structural calculations and warranties, product guarantees, as-built drawings, and an agreed snagging list before final retention is released. Missing paperwork is one of the most common problems raised when a property with recent building work is later sold.
Why the handover pack matters more than it feels like at the time
At the end of a project, the natural instinct is to enjoy the finished space and move on — the paperwork feels like an afterthought compared to actually living in the new kitchen or extension. But this is exactly the paperwork a conveyancing solicitor will ask for when you sell, and gaps in it can delay a sale, trigger indemnity insurance costs, or in some cases require retrospective inspection of work that's now hidden behind plasterboard.
Assembling the handover pack is far easier while the builder is still on site and everyone remembers what was done than it is two or five years later trying to track down a subcontractor who has since moved on.
Building Regulations completion certificate
Most structural work, extensions, loft conversions and significant alterations require Building Regulations approval, and on completion the Building Control body (either your local authority or a private approved inspector) should issue a completion certificate confirming the work complies. This is a distinct document from planning permission, and its absence is a red flag a solicitor will pick up on immediately when you sell.
- Confirm which Building Control body was used (local authority or approved inspector) and their reference number
- Request the completion certificate in writing if it hasn't arrived within a few weeks of final inspection
- Keep the full inspection history, not just the final certificate, where available
Competent person scheme certificates
Certain trades are allowed to self-certify their own compliance with Building Regulations under government-authorised competent person schemes, rather than requiring a separate Building Control inspection for that element. If your project included electrical work, gas work, or replacement windows/doors, you should receive the relevant scheme certificate.
- Electrical installation certificate (Part P) from a registered scheme member — see GOV.UK's competent person scheme register
- Gas work certificate from a Gas Safe registered engineer
- FENSA or equivalent certificate for replacement windows and external doors
- Any other trade-specific certification relevant to the work carried out
Structural calculations and warranties
Where structural work has taken place — steel beams, removed walls, underpinning, new foundations — you should hold the structural engineer's calculations, and ideally a structural warranty if one was arranged. These documents matter both for Building Control compliance and because a future buyer's surveyor will ask for them if they spot evidence of structural alteration.
- Structural engineer's calculations for any steel, beams or load-bearing alterations
- Structural warranty documentation if a warranty scheme was used
- Details of any remedial structural work (e.g. underpinning) with supporting reports
Product guarantees and as-built information
Manufacturer guarantees on windows, boilers, roofing materials, damp-proofing systems and similar products are only useful if you actually hold them and know how to register a claim. As-built drawings — showing the finished layout, structural elements and service runs — are equally valuable, particularly if you ever need to know where a drain, cable or steel beam actually sits rather than where it was originally drawn.
- Manufacturer guarantees for boiler, windows, roofing, damp-proofing or other specified products
- Instructions for registering guarantees where required (some need registration within a set period)
- As-built drawings showing final layout and structural elements
- Service drawings showing the actual position of drainage, electrics and plumbing runs
Air testing, EPC and energy compliance
Depending on the scope of work, an air-tightness test may be required to demonstrate compliance with thermal efficiency requirements under the Building Regulations, and a new or updated Energy Performance Certificate (EPC) may be needed — particularly relevant for larger extensions or where the property is being sold or let. Ask your Building Control body whether these apply to your project.
Snagging: how to run it properly
Snagging is the process of identifying and listing defects or unfinished details before final sign-off — anything from a poorly finished paint edge to a door that doesn't close properly. It works best as a structured walkthrough with the builder present, item by item, written down and dated, rather than a vague verbal conversation.
- Walk the whole project room by room with the builder, noting every item however small
- Put the snagging list in writing with photographs and a date, and agree it with the builder
- Agree a timeframe for snagging items to be resolved
- Re-inspect once items are marked complete before considering the job fully closed
Releasing final retention
If your payment schedule included a retention — a small percentage held back specifically for snagging and defects — it should only be released once the agreed snagging items are resolved to your satisfaction, not simply once the builder asks for it. This is the leverage that ensures small defects actually get fixed rather than becoming your problem to sort later.
Why all of this matters when you sell
When a property with an extension, loft conversion or significant alteration goes to sale, a buyer's solicitor will typically ask for the Building Regulations completion certificate and any relevant competent person certificates as standard conveyancing enquiries. Missing documentation doesn't necessarily stop a sale, but it commonly leads to delay, negotiation over price, or the cost of indemnity insurance or a retrospective regularisation application — all avoidable by keeping the handover pack together from day one.
Practical checklist
- Building Regulations completion certificate received and filed
- Building Control body and reference number recorded
- Electrical installation certificate (Part P) obtained if relevant
- Gas Safe certificate obtained if gas work was carried out
- FENSA or equivalent certificate obtained for replacement windows/doors
- Structural engineer's calculations held for any steel or load-bearing alteration
- Structural warranty documentation held if a warranty scheme was used
- Manufacturer guarantees collected for boiler, windows, roofing and similar products
- Guarantee registration completed within any required timeframe
- As-built drawings obtained showing final layout and structural elements
- Service drawings obtained showing actual drainage/electrics/plumbing runs
- Air test results obtained if applicable to the scope of work
- Updated EPC obtained if applicable
- Full room-by-room snagging walkthrough carried out and documented
- Snagging list agreed in writing with the builder, with a resolution timeframe
- All snagging items re-inspected before being marked complete
- Retention held back until snagging is genuinely resolved
- All documents stored together in one place for future sale
Good and bad examples
What good looks like
A homeowner keeps a single folder (physical and scanned) containing the completion certificate, electrical certificate, structural calculations, guarantees and as-built drawings, assembled while the builder was still on site. When they sell three years later, their solicitor's enquiries are answered within a day.
What to push back on
A homeowner pays the final invoice, thanks the builder and doesn't chase the paperwork. Two years later, at the point of sale, they discover no Building Regulations completion certificate was ever issued for the extension, and the buyer's solicitor requires either retrospective regularisation or indemnity insurance before the sale can proceed.
Worked example
Illustrative handover pack — items and who typically issues them.
| Document | Typically issued by | Why it matters |
|---|---|---|
| Building Regulations completion certificate | Building Control body/approved inspector | Confirms statutory compliance; needed for sale |
| Electrical certificate (Part P) | Registered electrician/scheme | Confirms electrical work is compliant |
| Gas Safe certificate | Gas Safe registered engineer | Confirms gas work is compliant and safe |
| FENSA/window certificate | Window installer/scheme | Confirms replacement glazing compliance |
| Structural calculations | Structural engineer | Evidences load-bearing changes |
| Product guarantees | Manufacturer/supplier | Covers defects and failures post-completion |
| As-built drawings | Architect/builder | Records actual finished layout and services |
Commonly missed items
- Building Regulations completion certificate never chased once the invoice is paid
- Electrical or gas certificates assumed to exist but never actually requested
- Structural calculations left with the engineer and never passed to the homeowner
- Product guarantees not registered within the manufacturer's required period
- Snagging done verbally rather than in writing, so nothing is enforceable
- Retention released before snagging items are actually completed
Warning signs
- Builder is reluctant to confirm which Building Control body was used
- No mention of certification at all as the project nears completion
- Pressure to release final retention before snagging has been walked through
- Vague answers about who carried out electrical or gas work and whether they are registered
Questions to ask
- Which Building Control body is inspecting this work, and when should I expect the completion certificate?
- Who is issuing the electrical and gas certificates, and are they registered with a competent person scheme?
- Will I receive structural calculations and any warranty documentation directly?
- Are as-built drawings being produced, and can I have a copy?
- Is an air test or updated EPC required for this scope of work?
- When will we walk the snagging list together, and what's the agreed timeframe for fixes?
When to seek professional advice
- If a completion certificate has not arrived within a reasonable period after final inspection — contact the Building Control body directly
- If you discover, on selling, that Building Regulations approval was never obtained — a solicitor or your local authority Building Control can advise on regularisation
- If you are unsure whether a competent person certificate is required for work already carried out
- If a builder disputes the snagging list or refuses to complete agreed items before retention is released
Official sources
Frequently asked questions
- What happens if I sell without a Building Regulations completion certificate?
- It doesn't automatically stop a sale, but a buyer's solicitor will usually flag the gap and require either a retrospective regularisation application to the local authority or indemnity insurance to cover the risk — both add cost and delay that are avoidable by chasing the certificate at the time.
- Do I need an electrical certificate for minor electrical work?
- Notifiable electrical work (most new circuits, consumer unit changes, and work in kitchens or bathrooms) needs to be certified either by a registered competent person or via Building Control. Ask your electrician directly whether the work carried out was notifiable.
- When should retention be released?
- Only once the agreed snagging list has been resolved and re-inspected to your satisfaction — retention exists specifically to give you leverage to get small defects fixed after the main work is finished, so releasing it early removes that leverage.
- What is an as-built drawing and do I really need one?
- It's a drawing showing the finished layout and structural elements as actually built, which can differ from the original design drawings. It's genuinely useful later — for example, knowing exactly where a steel beam or drain run sits before you drill into a wall or plan future work.
- Who issues a Building Regulations completion certificate?
- Either your local authority's Building Control department or a private approved inspector, depending on which route was used for the project. It's issued once the final inspection confirms the work complies with the relevant regulations.
Builder Proof UK publishes general educational information for homeowners. It is not legal, structural, surveying, planning, electrical, gas, insurance or financial advice, and it does not replace advice from a suitably qualified professional for your specific project.