What Architects Need Before Design Starts
For planning applications in the UK, architects need two core surveys before design starts: a measured building survey (for existing structures) and a topographical survey (for the land and site).
What Each Survey Provides
| Survey Type | What It Captures | When It's Needed | | --- | --- | --- | | Measured Building Survey | Internal floor plans (room sizes, walls, doors, windows, stairs), external elevations (heights, rooflines, window positions), ceiling heights, spot levels, sections | Any project involving existing buildings: extensions, conversions, renovations, change of use | | Topographical Survey | Site boundaries, building footprints, ground levels/contours, trees (with canopy spread), walls/fences, drainage covers, utilities, kerbs, access points, spot heights | New builds, significant extensions, sloping/irregular sites, sites with trees, drainage/SuDS requirements |
Why These Are Essential Before Design
- Accuracy prevents refusal — Submitting drawings based on outdated OS maps or rough measurements is a common cause of planning delays and refusals
- Design feasibility — Architects need precise dimensions to create schemes that fit the actual site and building constraints
- Regulatory compliance — Accurate data ensures proposals meet local planning requirements and building regulations
- Reduces costly errors — Wrong measurements lead to design revisions, drainage issues, neighbour objections, or construction cost overruns
What to Expect as Deliverables
- CAD drawings and PDF plots (sometimes 3D models)
- OS-coordinated site plans with boundaries and footprints
- Internal/external elevations and floor plans to scale
Timing: Allow a few weeks for survey results — arrange it early in your project timeline.
Common Planning Application Requirements
Most planning applications require:
- Existing site plan — showing the property footprint, boundaries, adjacent structures, and access
- Existing floor plans — all levels showing current layout
- Existing elevations — all four façades showing current appearance
- Existing sections — cross-sections showing floor-to-ceiling heights and construction
- Topographical plan — where the site has significant level changes, trees, or drainage features
Note: While architects can develop initial concept ideas using estate agent drawings, a professional measured survey is crucial before submitting a planning application.
Frequently Asked Questions
Q: Can I use estate agent floor plans for a planning application?
No — planning applications require accurate, to-scale drawings based on actual measured survey data. Estate agent plans are not to scale and are not acceptable.
Q: Do I need both a measured building survey and a topographical survey?
For most planning applications involving existing buildings, yes — the measured building survey covers the structure and the topographical survey covers the land. For simple house extensions, a measured building survey alone may suffice.
Q: How long does a measured survey for planning take?
On-site: 1–2 days. Office processing: 3–5 working days. Total: typically 5–10 working days from instruction to delivery.