Who can sign off a structural appraisal for a conversion
No statute names the qualification, but a conversion appraisal carries weight when a chartered engineer has inspected the building, states the limitations and answers the capable of conversion question directly.
A structural appraisal supporting a conversion application should be written and signed by a chartered structural or civil engineer who has inspected the building, carries professional indemnity cover and is prepared to state a conclusion on whether the building is capable of conversion. No statute names the qualification, which is why the question keeps coming up. In practice a structural appraisal for conversion is accepted where the author is a chartered member of the Institution of Structural Engineers or the Institution of Civil Engineers, the inspection is described, and the limitations are set out rather than buried.
For a prior approval conversion the appraisal is doing something narrower and harder than a general condition survey. It has to answer the conversion question.
Why a conversion application needs structural evidence
Class Q of Schedule 2 Part 3 of the General Permitted Development Order 2015 allows an agricultural building to become a dwellinghouse, and Class MA allows certain commercial floorspace to become residential. Both are drafted around the idea that an existing building is being converted, with building operations limited to what is reasonably necessary.
That drafting is where the structural appraisal earns its fee. If the works go beyond conversion and amount to a rebuild, the class does not apply, the prior approval cannot lawfully be granted, and a permission obtained on a false premise is vulnerable. The leading authority is Hibbitt v Secretary of State for Communities and Local Government [2016], which drew the line between converting a building and erecting a new one inside a retained frame.
Authorities read appraisals with that case in mind. An appraisal that says the building is in poor condition but could be made good with new foundations, new external walls and a new roof structure is, on its own terms, describing a rebuild.
Chartered status and insurance
The qualification to look for is MIStructE or FIStructE from the Institution of Structural Engineers, or MICE or FICE from the Institution of Civil Engineers with relevant structural experience. Chartered status means an assessed route to competence and a code of conduct with a complaints mechanism behind it.
Professional indemnity insurance matters more than clients expect. The appraisal is a document a decision rests on, and if it proves wrong the cost of unwinding the position falls somewhere. Ask for the level of cover, whether it is on a claims-made basis, and whether the author's practice will carry it for the life of the development. A sole practitioner approaching retirement is not the same risk as a practice with run-off cover.
Reliance letters are the other practical item. Where a lender or purchaser will rely on the appraisal, say so before the appointment rather than asking for an assignment afterwards.
What the appraisal has to conclude
A useful appraisal does four things. It identifies the structure as built, with materials, spans, frame type, foundation evidence and visible defects. It states the loading the conversion will impose, including any change of floor use. It says whether the primary structure can carry that loading with works limited to those permitted by the relevant class. And it says what those works are.
A conclusion of the form "the building is structurally sound subject to further investigation" is of little use, because it defers the only question being asked. Push for a view.
Expect the appraisal to address, explicitly:
- The condition and adequacy of the foundations, with the basis of that view stated.
- Frame or wall capacity for a residential floor loading and for a new or replacement roof covering.
- Lateral stability, which is the usual failure point in open-sided agricultural structures.
- Whether the external envelope can be replaced as permitted, or whether the walls themselves are doing structural work that cannot be removed.
- Whether any part requires demolition beyond what is reasonably necessary.
Capable of conversion against rebuilt
The distinction turns on what survives. A steel portal frame in sound condition, with slab and stanchion bases that can take residential loading, is a building capable of conversion even if every sheet of cladding is replaced. A collapsing brick barn with no roof, where the walls would have to be taken down and rebuilt to take a floor, is not, however sympathetic the end result.
The honest uncertainty here is the middle ground. Partial replacement of a wall, new pad foundations under an existing stanchion, or underpinning are each arguable, and authorities take different views. The appraisal should quantify the extent of intervention as a proportion of the primary structure, in square metres or linear metres, so the officer has a figure rather than an adjective to work with.
Where the answer sits in that middle ground, a full planning application for a replacement dwelling is often the faster route, even in the countryside where policy is harder. A refused prior approval followed by an appeal costs a season.
Survey access and opening up
Most appraisals are visual inspections of accessible parts. That is a real limitation when the question is foundation adequacy, because foundations are not visible. Where the conclusion depends on them, the appraisal should be supported by one or more trial pits, and the pit locations and findings should be in the report.
Other common limitations worth negotiating before the appointment:
- Access to roof structures, which may need a tower or a drone survey rather than a view from the ground.
- Removal of a small area of cladding or plaster to inspect connections and bearings.
- Moisture and timber decay assessment where a timber frame is involved, which may need a separate specialist.
- Asbestos, which usually stops opening up until a survey is in place.
A report full of caveats about what could not be seen invites a condition requiring further structural information, and that condition can be difficult to discharge if the answer turns out to be unwelcome.
Who the authority will accept
Authorities rarely publish a list of acceptable qualifications for structural evidence. What they do is read the report and decide whether it carries weight. Three things move that assessment: named chartered status with a membership number, a description of the inspection actually carried out with dates, and a signed conclusion rather than a hedged one.
Where a review or second opinion is needed, the route through a directory of professional reviewers is the practical one, particularly for an investor without an existing engineer. The same competence questions arise across the other technical documents in a submission, and the reasoning is similar to the one set out for drainage engineer competence.
If an engineer is replaced partway through, the handover needs care, for the reasons described in the note on changing consultant mid-application. A second appraisal that contradicts the first is a problem the authority will notice.
Coordinating with the submission
Sequence matters. Commission the appraisal before the architect fixes the layout, because the structural answer may rule out the mezzanine, the dormers or the opening widths the design depends on. Then let the appraisal inform the description of works in the prior approval submission, so the two documents describe the same building operations.
The written submission should summarise the appraisal rather than leave the officer to extract it. A paragraph naming the author, their chartered status, the inspection date and the conclusion, cross-referenced to the appendix, is enough. The index of report types shows where the structural document sits alongside the rest of a conversion pack.
Draft the supporting documents for a conversion on PlanScope, then send them to a chartered engineer and a reviewer before they go to the council.
This is general guidance, not legal advice; check the position with your local planning authority or a qualified professional before relying on it. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval. For specialist technical reports, qualified professional input may be required.
Frequently asked questions
Does a structural appraisal for Class Q have to be by a chartered engineer?
No statute requires it, but chartered status is what gives the report weight. Look for MIStructE or FIStructE from the Institution of Structural Engineers, or MICE or FICE from the Institution of Civil Engineers with structural experience. Chartered membership brings an assessed competence route and a code of conduct with a complaints mechanism behind it.
What does capable of conversion mean in practice?
It means the primary structure can carry the loading of the new use with building operations limited to those the permitted development class allows. A sound steel portal frame with adequate bases qualifies even if all the cladding is replaced. A roofless barn whose walls must be taken down and rebuilt does not, because that is erection rather than conversion.
Can an appraisal be based on a visual inspection only?
It can, but foundation adequacy cannot be judged by looking. Where the conclusion depends on the foundations, ask for trial pits and have the locations and findings recorded in the report. A report heavy with caveats about what could not be inspected tends to attract a condition requiring further structural information.
Why does professional indemnity insurance matter for this report?
The prior approval decision rests on the appraisal, so if the conclusion proves wrong the cost of unwinding falls somewhere. Ask about the level of cover, whether it is written on a claims-made basis, and whether run-off cover will be maintained. Raise any lender or purchaser reliance before the appointment, not afterwards.
What if the structural answer is borderline?
A full planning application for a replacement building is often faster than a contested prior approval, even where countryside policy is harder to satisfy. Ask the engineer to quantify the extent of intervention in square or linear metres as a proportion of the primary structure, so the officer has a measured figure to weigh.
Sources and further reading
This article is general guidance about the planning system in England and, where stated, the rest of the UK. It is not legal or professional advice. Check your local planning authority’s validation requirements and take professional advice for your specific site.