How does a post-completion Building Warranty work?

If your property is already built but was never covered by a structural warranty, a post-completion warranty can still be arranged. 

It’s a routine situation for self-builders, small developers, and sellers whose sale has stalled because a buyer’s lender flagged the missing cover. It’s just as common on the buyer’s side too, falling for a property that ticks every box, only to find it’s missing the cover a lender will need before releasing funds. 

Here’s how the process actually works, what a surveyor checks, and when a Professional Consultants’ Certificate might be the better route instead.

What Is a Post-Completion Building Warranty?

A post-completion building warranty, also called a retrospective building warranty, is a structural warranty arranged after construction has already finished, rather than before work begins. It covers major structural defects in the completed property, and cover runs for the remainder of the standard 10-year term measured from the property’s original completion date, not from the date the new policy is issued.

Without a Building Warranty, sellers will find it hard to persuade potential buyers that the property is safe to invest in. Most buyers will at least partially rely on a mortgage lender, too, and lenders are unlikely to finance their purchase if there is no proof of a warranty that can protect their investment.

A post-completion warranty resolves that gap. At ABC+ Warranty, we issue this as our Completed House Warranty, built to the same standard as a warranty arranged before construction started.

Why This Situation Comes Up

Several situations commonly lead to needing cover after the fact:

• The original developer never arranged one. Small developments and self-builds are sometimes completed without a warranty scheme in place from the outset.
• Cover lapsed or was never finalised. A warranty application started before completion can stall or expire if it isn’t followed through to issue.
• A sale has surfaced the gap. A buyer’s mortgage lender flags the missing warranty during conveyancing, often well after the building itself is finished.
• A remortgage requires it. Lenders typically expect a structural warranty to still be in place within its original 10-year term, even years after completion.

How the Post-Completion Inspection Works

Every structural warranty relies on a chartered surveyor monitoring the build in stages, typically at foundation, frame, weathertight, and completion. This staged process lets the surveyor catch problems as they happen, before they’re covered by finishes or plasterwork.

A retrospective case skips those stages entirely. The surveyor sees only a finished building, so the single post-completion inspection has to do the work of several. In practice, this means:

• A full condition survey of the structure, from foundations to roofline
• Requests to open up finished areas, such as flooring or wall linings, where the surveyor can’t otherwise confirm what’s underneath
• A more cautious approach to any element that can’t be fully verified

Surveyors carrying out this work are typically chartered through RICS or CIOB, and the technical standard they apply doesn’t change because the build has already finished.

Retrospective Structural Warranty or Retrospective PCC: Which Fits?

A structural warranty isn’t the only way to satisfy a lender. A retrospective Professional Consultants’ Certificate, or PCC, is a second route worth considering. It can be faster and less expensive to arrange, though the protection it offers is narrower.

Retrospective Structural Warranty

• What it confirms: ongoing cover for structural defects
• Claim route: direct claim against the warranty policy
• Typical duration: remainder of the original 10-year term
• Cost: generally higher, reflecting broader cover

Retrospective PCC

• What it confirms: the build complies with approved plans and Building Regulations
• Claim route: must prove the consultant was negligent
• Typical duration: 6 years from issue
• Cost: generally lower

If speed and cost matter more than the breadth of cover, a PCC may be the better fit. We cover this comparison in more depth, including how switching between the two works, in our guide to what a CML certificate (PCC) covers.

Cost, Timeline and What Affects the Outcome

Retrospective cover typically carries a higher premium than a warranty arranged before construction starts. This reflects the reduced ability to inspect the build as it happened. A few factors tend to drive the cost and outcome of any individual case:

• The age of the property and how much original build documentation survives
• How much opening up the surveyor needs to request
• Whether any elements are likely to need exclusion or remedial work before a certificate can be issued

Because there’s only one inspection rather than several staged visits, the process is often quicker to complete than a standard warranty, even though the underwriting behind it is more involved. 

Get in touch for a realistic cost and timeline based on your specific property, rather than a generic estimate.

What Happens If the Property Doesn’t Pass Inspection?

Failing a post-completion inspection outright is rare. More often, the surveyor identifies specific issues that need addressing before a certificate can be issued, and the warranty is delayed rather than refused while the work is completed and re-checked.

Where an issue can’t be resolved or fully verified, for example because the relevant area was covered over before an inspection could take place, a policy can sometimes still be issued with that specific item excluded. 

Cover then applies to everything else, and the exclusion is limited to whatever couldn’t be confirmed rather than the whole property.

With more at risk, issuing retrospective warranties requires a higher level of trust and exacting standards of expertise, which is why post-completion warranties are likely to have higher premiums – but the protection they provide is surely worth it.

Getting a Post-Completion Warranty Through ABC+ Warranty

If your build ran into trouble arranging cover in time, or you’re trying to rescue a sale that’s stalled over a missing warranty, ABC+ Warranty can help. Our Completed House Warranty covers exactly this situation, from the initial survey through to a policy that satisfies mainstream lenders.

When you come to us, we can discuss your circumstances in detail and help you to find the right cover for your completed construction project or ready-to-buy home. We provide Building Warranties for a variety of property types, at various stages.

If a PCC looks like the better fit for your situation, our team can talk you through that route instead. You can also check which lenders currently accept our certification on our Warranty Lender List.

in touch to discuss your property: call 0161 928 8804, message us on WhatsApp, or email info@architectscertificate.co.uk.

FAQs

Can I get a building warranty after construction is already finished?

Yes. A post-completion, or retrospective, warranty covers major structural defects for the remainder of the original 10-year term, even though construction has already finished.

Is a post-completion warranty more expensive than one arranged before the build starts?

Generally, yes. Insurers take on more risk without staged inspections during construction, and that’s typically reflected in a higher premium.

What happens if my property doesn’t pass the retrospective survey?

Outright refusal is rare. More often, specific issues need resolving first, or a policy is issued with those particular items excluded.

Do all mortgage lenders accept post-completion warranties?

Acceptance varies by lender, so it’s worth checking your lender’s position, or ours, via our Warranty Lender List, before applying.

Can I get a PCC instead of a full retrospective warranty?

A retrospective Professional Consultants’ Certificate is often faster and cheaper to arrange, though it offers narrower protection than a structural warranty. See our PCC guide for the full comparison.