Specification defects at contract issue
The six defects found most often in UK specifications when they become contract documents, how often each appears, and the specific check that catches each one before issue.
Which specification defects are most common at contract issue?
The most common defects in UK specifications at contract issue are internal contradictions (94% of documents), orphan references (88%), leftover master content (82%) and open TBCs (76%), followed by drawing-spec mismatches (71%) and withdrawn standards (40%). Each can be caught before issue with a specific, repeatable check, and the checks matter more than the authoring tool.
The figures come from Avoice's State of UK Specifications 2026, which graded 50 real UK specifications issued to tender or contract in 2026. Every document had at least one coordination defect, and the median document had 12. Quality judgements, such as whether a product choice was sensible, were excluded. Only defects that anyone could check and agree on were counted.
The median contract-issue document had 9 contradictions and 14 open TBCs. These are the normal state of a UK specification at the point it becomes a contract document, not edge cases.
The authoring tool made no difference: specifications written in dedicated software carried the same defects as those written in Word. Defects were linked to the absence of a final review step.
Internal contradictions
An internal contradiction is two clauses that specify the same element differently. It is the most common defect and the one most likely to become a dispute, because the contractor can price the cheaper reading and claim the dearer one as a variation.
Typical patterns, drawn from Avoice's QC review of a widely used published sample specification:
- A facade section naming Class B panels while requiring A2-s1,d0 infill in the same section.
- A window specified to non-fire-rated standards in one item and E30/I30 in another.
- A product named as a 40 mm board with a thickness attribute of 120 mm.
- A balustrade option of "No handrail" in a clause that then specifies stainless handrails.
- A screed described as dry in 48 hours but requiring a seven-day cure.
Reading section by section hides contradictions that sit pages apart. Pulling every mention of an element together makes them obvious.
How to catch it: for each key element, list every clause that mentions it across the whole document and confirm that product, performance values and standards agree. Pay particular attention to clauses where a named product sits alongside a performance requirement: if the product cannot meet the performance, the clause contradicts itself.
Orphan references and leftover master content
An orphan reference points to something that is not in the issued set. Leftover master content describes scope that is not in the project. Both are found in more than four out of five contract documents.
Orphan references (88%)
"Refer to the acoustic report", "as drawing 1234-P-201" or "see clause 330" where no such item exists. A contractor cannot price what they cannot see, and the gap is usually filled by the contractor's assumption.
How to catch it: extract every external reference (drawing numbers, schedules, consultant reports, standards) and every internal cross-reference, and tick each one against the actual issue register and the document's own clause list. Do this after the final round of revisions, because renumbered clauses and superseded drawings create orphans late.
Leftover master content (82%)
Text carried over from the practice master, a previous project or a template. Examples from the sample specification review include a restaurant furniture clause headed "Classroom Storage" carried over from an education template, plasterboard execution clauses attached to non-gypsum boards, and seam layouts for roll materials applied to tiles and planks.
Heading: Classroom Storage Content: restaurant furniture
Heading from an education template on a restaurant project. Reveals its origin and can still be priced.
Refer to the acoustic report → issue register: not issued → add to register, or delete
Each reference is ticked against the issue register after the final revision, not before.
Some leftover content is inert and graded minor. But a clause describing work not in the project can still be priced, and one describing the wrong installation method can be followed.
How to catch it: for every section, ask "is this work in the project?" and delete rather than leave clauses "just in case". Search for words that reveal origin: building types, client names, place names and project numbers that do not belong. Content with no counterpart on any drawing is a strong signal.
Why open TBCs are a defect at contract issue
An open TBC is an explicit unresolved item in an issued document. At Stage 4 they are expected and every document in the study had them, but 76% still had them at contract, with a median of 14.
The report's warning is that whatever is open at tender is usually still open at signature. When a TBC sits on a priced item, it is graded major: it will take an instruction to resolve, and that instruction usually costs money.
Whatever is open at tender is usually still open at signature.
How to catch it: keep a TBC register outside the document, with an owner and a date for each item, and search the document for every placeholder form your practice uses (TBC, TBA, ???, [insert], highlighted text) before every issue. Ideally none remain on priced items. Each remaining item should be:
- Closed
- Resolved by the design team before issue.
- Provisional sum
- Converted, so the cost risk is visible in the tender.
- Contractor design
- Explicitly passed to the contractor as a design responsibility.
Our guide to TBCs in specifications at tender covers the process in detail.
Drawing-spec mismatches and withdrawn standards
Drawing-spec mismatch is the only defect class that grows as a project approaches contract. Withdrawn standards are rarer but can be critical where requirements have changed.
Drawings keep changing after the specification has been checked, and few practices re-check the specification against the final drawing set.
How to catch a mismatch: make a spec-to-drawing pass a mandatory step at every issue, not just at Stage 4. Compare drawing notes, keys and schedules with specification references: product codes, door and window types, fire ratings, finishes. The report found that practices without this final pass accounted for most high-severity defects.
Withdrawn standards (40%)
Where the successor is materially identical, citing a withdrawn standard is minor; where requirements have changed, it can be critical. Check every cited standard's status against the publisher's catalogue at issue, and watch for recent changes. BSI states that BS 7671:2018+A2:2022+A3:2024 is withdrawn on 15 October 2026 in favour of BS 7671:2018+A4:2026. Also check the right standard is cited for the right property: reaction to fire and fire resistance, for instance, are classified under different standards.
What a good pre-issue checking routine looks like
A practical order of work, highest risk first. The report's view is that this is "a missing step, not a missing skill": nobody re-reads the whole document against itself and the drawings at the end.
- Fire, structural and thermal values on every safety-related element, checked across all clauses.
- Contradictions by element.
- Spec-to-drawing pass against the current drawing set.
- TBC sweep against the register.
- References: internal cross-references, external documents and standards.
- Leftover content: section-by-section scope check.
- Record the check, its date and the issue it relates to.
The people writing specifications know what good looks like. For the legal side of what happens when this step is missed, see 1 in 5 UK specifications went to tender with legally consequential errors.
Where Avoice fits
Every one of these checks is objective, which means it can be run on every issue rather than only when someone has time.
Avoice QA/QC runs these checks automatically on any specification, whether written in Avoice or elsewhere: contradictions, orphan references, leftover content, open TBCs, spec-to-drawing mismatches and withdrawn standards, each graded by severity. Specifications drafted in Avoice's spec writing are checked as they are written, so the final pass starts from a cleaner document.
Software can find and grade defects. The specifier still decides how each one is resolved and signs off the issue.
See a defect report on your specification
Contradictions, orphan references, leftover content, open TBCs, drawing mismatches and withdrawn standards, each graded by severity, on any specification.
This guide is for general education and is not professional advice. Figures are from Avoice's State of UK Specifications 2026 sample of 50 documents and may not reflect every practice.