Structural survey reporting outline for a conversion
The planning-relevant question is whether the building can take the new loads without being substantially rebuilt. Write the report so that answer is findable and evidenced.
A structural survey supporting a conversion application has one planning-relevant output: whether the existing building can take the loads the new use imposes without being substantially rebuilt. Everything else in the report serves that finding. Officers are not assessing your steelwork. They are deciding whether what you have described is a conversion or a rebuild dressed as one, and on a Class Q barn or a Green Belt reuse that distinction decides the application. Write the report so the answer to that question is findable in the first page and evidenced in the rest.
Scope, limitations and access constraints
Open with what you were asked to do, what you inspected, and what you could not.
State the instructing party, the date or dates of inspection, the weather and ground conditions at the time, and the proposed use the appraisal is testing against. Then list the limitations honestly:
- Elements not inspected, such as foundations, concealed timbers, cavity ties or below-slab drainage.
- Areas without access, with the reason: locked, unsafe, occupied, obstructed by stored material.
- Whether opening-up works were carried out, and if not, why.
- Absence of calculations where the appraisal is qualitative at this stage.
- Any reliance on drawings, previous reports or third-party information, each identified.
A limitations section that reads as a disclaimer template will be treated as one. A limitations section that names the three specific things nobody could see, and says what would resolve them, reads as professional and supports a conditional approval.
The Institution of Structural Engineers publishes guidance on the appraisal of existing structures, and citing the approach you followed tells the reader what standard of appraisal this is.
Existing structural form described
Describe the building as it stands, element by element, so that a reader who has never visited can picture the load path.
Cover the foundation type and depth where known or inferred, the wall construction with thicknesses and materials, the floor construction and span direction, the roof structure with member sizes and spacings, and any frame, whether timber, steel, cast iron or concrete. Say how lateral stability is achieved, because in old agricultural and industrial buildings it is often achieved by nothing more than the roof covering and a few braced bays.
Include dimensions. A description that says "traditional brick construction" tells the reader nothing, while "solid brick, 340 mm, in lime mortar, with no evident wall ties and a maximum unrestrained height of 5.2 m on the north elevation" tells them everything.
Photographs belong here, numbered, with a key plan showing where each was taken from.
Condition of primary elements
Separate condition from adequacy. A wall can be in poor condition and structurally adequate once repaired, or in fair condition and inadequate for the loads proposed.
Report condition against each element: cracking with its pattern, width and whether it is live, deflection measured rather than estimated, timber decay and insect attack with the species of decay identified where possible, corrosion of embedded metalwork, moisture levels, and evidence of previous movement or repair. Say whether movement appears historic and stable or current, and how you reached that view.
Where a defect would be material to the planning decision, flag it as such in the text. A roof that has already partly collapsed is not a detail; it goes to whether the building is capable of conversion at all, and that is precisely the point on which appeals against Class Q refusals turn.
Load paths for the proposed use
This is the section the planning officer reads. Take the proposed layout and follow the loads down.
- State the new loadings: residential imposed loads, new floor build-ups, partitions, plant, any new openings.
- Identify where those loads land: existing walls, new beams, existing footings.
- Assess each load path for adequacy, with the assumptions stated and the sensitivity to unknowns noted.
- Identify where the existing structure cannot take the load and what intervention is therefore needed.
- Quantify the intervention as a proportion of the existing fabric affected.
That last step is the one people leave out, and it is what allows an officer to judge the scale of works. Where a conversion needs a new internal frame, new foundations under every wall and a replacement roof structure, the honest conclusion is that the building is being rebuilt around a facade, and the planning consequence of that conclusion belongs in the Planning Statement rather than being buried.
For permitted development conversions under Part 3 of the GPDO, the legal test is that the building must be capable of functioning as a dwelling with works no more extensive than those the class permits. Appeal decisions on this point are indicative of how inspectors approach it rather than binding, and the pattern is consistent: a structure needing wholesale replacement of its primary elements is not converted, it is replaced.
Opening up works and their findings
Where opening-up has been carried out, report it as a distinct exercise.
Give the location of each opening with a reference on the plan, its size, what was exposed, the date, and who supervised it. Then the findings: foundation depth and type at each trial pit, bearing material, groundwater encountered, wall core construction, joist end condition where a floor was opened, lintel presence over openings.
Trial pits beside a rubble foundation on a nineteenth-century barn routinely find 300 mm of unmortared stone on subsoil. That is a finding with design consequences and it is better in the report than discovered on site. Where opening-up has not been done, say what you would open up and at what stage, and expect a condition requiring it.
Strengthening proposals and feasibility
Describe the interventions in enough detail that their scale is clear, without pretending to have designed them.
For each deficiency identified, give the proposed remedy, its extent, and any consequence for the appearance of the building: underpinning or mass concrete beneath specified wall lengths, new padstones and lintels at new openings, tying of the wall head to a new ring beam, a new independent floor structure, a new roof structure within the existing profile, or localised rebuilding where the fabric has failed.
Then state feasibility plainly. Deliverable with standard techniques, deliverable with specified temporary works, or not deliverable without substantial rebuilding. The middle option usually needs a temporary works note, because propping a stone barn while a ring beam goes in is a real design exercise and one that affects whether the historic fabric survives the process.
Where the building is listed or in a conservation area, the strengthening scheme and the heritage case have to agree with each other, and the Design and Access Statement is where that reconciliation is shown. A barn conversion carries this tension more than any other building type, as the note on the design and access statement for a barn conversion sets out.
Residual risks for the planning decision
Close with what remains unknown and what it would change, in a short numbered list rather than prose.
State each residual risk, the trigger that would reveal it, the likely design consequence, and whether it can be managed by condition. Foundation adequacy pending trial pits. Timber condition pending removal of finishes. Wall tie condition pending a borescope survey. Lateral stability pending analysis once the roof covering is stripped.
The value of this section is that it gives the officer a route to approval. A report saying "subject to confirmation of foundation depth by trial pit, the proposed load paths are feasible" invites a pre-commencement condition. A report saying nothing about what is unknown invites a refusal on the grounds that the case has not been made.
A Structural Survey drafted this way is also the document a purchaser's engineer will read, so write it for both audiences and date every statement.
Enter your postcode on PlanScope to see which documents a conversion application on your building is likely to need.
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.
Frequently asked questions
What does a planning officer look for in a structural survey?
Whether the proposal is a conversion or a rebuild. They want the new loadings, where those loads land, which parts of the existing structure cannot take them, and how much of the existing fabric the strengthening works affect. That proportion is what tells them whether the building is being converted or replaced.
Does the report need calculations?
Not usually at application stage. A qualitative appraisal with stated assumptions is normally enough, provided it identifies each load path and says whether it is adequate. What matters is that the limitations are explicit, so that a condition can require detailed design and any opening-up works before construction starts.
How much detail should the limitations section contain?
Enough to be useful. Name the specific elements not inspected, the areas without access and the reason, whether opening-up was carried out, and what reliance was placed on third-party information. A generic disclaimer is treated as boilerplate, while three named unknowns with the resolution route supports a conditional approval.
Why does structural condition matter for a Class Q barn conversion?
Because the permitted development route requires the building to be capable of functioning as a dwelling with works no more extensive than the class permits. A structure needing wholesale replacement of its primary elements fails that test. Appeal decisions on the point are indicative rather than binding, and they are consistent.
What belongs in the residual risks section?
Each unknown, the trigger that would reveal it, the likely design consequence, and whether it can be managed by condition. Typical entries are foundation adequacy pending trial pits, timber condition pending removal of finishes, and lateral stability pending analysis once the roof covering is stripped.
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.