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Need a quick price for your project? Get a quote
[email protected] | 020 8935 5160
Need a quick price for your project? Get a quote
Article By: Tom Ayre
Last Update: January 2026
On large apartment schemes, area figures are not just a technical detail. Net Sales Area (NSA) often feeds into commercial decisions, including rental and sale valuations. That’s why many developers and QS teams commission NSA verification during the build programme, so they have a clear, RICS-aligned view of what has actually been constructed.
At THS Concepts, we carry out NSA verification surveys using 3D laser scanning, then issue easy-to-use plans and a comparison schedule showing theoretical (design) areas against the as-built areas we measure on site.
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NSA is the internal floor area of a unit, typically measured to the internal face of external and party walls. It’s used to quantify the sellable or lettable space within an apartment, and calculations are commonly prepared in line with the RICS Code of Measuring Practice.
In practice, NSA verification is about consistency and clarity across a development. You want figures you can rely on, presented in a way that can be checked and applied across a full schedule of units.
Most NSA verification work is requested during the build phase, often as units become ready in batches. The driver is usually commercial: confirming areas for valuation and reporting, and ensuring the as-built accommodation aligns with what is expected from the design information.
Our role is straightforward:
You provide the theoretical or design areas (often in an Excel schedule)
We provide the as-built NSA figures and drawings
We return a clear comparison so variances can be reviewed by your commercial team
We keep the outputs practical for project teams:
PDF floor plans for each unit, illustrating key figures such as NSA
An updated spreadsheet comparing theoretical (design) areas against the as-built NSA we measure
This format works well on large schemes where the schedule matters as much as the individual plan.
On site, we typically liaise with the site manager, who coordinates access to the units being measured. We use 3D laser scanning to capture the as-built internal geometry efficiently, which helps on developments where access windows are tight and units are at different stages of completion.
We can measure bare units or finished, furnished apartments. The main requirement is that the internal layout is established, for example plasterboard is up and the space is suitably defined for measurement. We can usually work around other trades, provided activities in the unit are not too intensive at the time.
A typical turnaround is within five working days of being on site, depending on unit volumes and programme.
To quote accurately and keep delivery smooth, we normally ask for:
A unit list and site programme or access plan
Your theoretical/design area schedule (Excel is ideal)
Any drawing sets or layouts that help identify unit types and numbering
We’ve completed a high volume of NSA verification surveys across the UK, including large residential developments in London. Recent work includes Capital Interchange (232 apartments) and 239 Mill Road, where the priority was producing consistent plans and area figures across a large unit schedule within a live construction programme.
NSA verification is usually commissioned once the unit layout is fixed and measurable, and before commercial reporting needs the final numbers.
In practical terms, that tends to be:
During fit-out / late-stage construction, once partitions are in (for example plasterboard up) and room extents are clearly defined.
In batches as units become available, rather than waiting for the whole block.
At or near Practical Completion, where the as-built record is needed for sign-off and downstream use.
A typical NSA verification pack is designed to be usable by QS and developer teams without reworking:
PDF unit floor plan(s) showing the measured NSA figure(s) clearly.
An area schedule (Excel) updated with:
client-provided theoretical/design NSA
THS measured as-built NSA
variance (m² and ft², and often % if requested)
notes/assumptions where needed (for example unit not fully accessible).
A brief methodology and measurement basis note, so the figures are auditable and consistent across the schedule.
On large schemes, access is normally the limiting factor, not measuring. The cleanest approach is:
Coordinate with the site manager for a unit list, access windows, and any restrictions (keys, permits, sign-in, PPE).
Work in a planned route (by stack, core, or floor) to reduce travel time and repeated escorting.
Scan efficiently and stay out of the way, working around trades where possible, and returning later only if a unit is too busy or unsafe.
Record constraints immediately (locked rooms, snagging activity, areas not ready) so the schedule and drawings stay consistent.
For residential schemes, the important thing is to agree and document the measurement basis upfront, then apply it consistently across every unit.
Commonly used bases include:
RICS Code of Measuring Practice (6th edition) definitions where applicable, with the measurement basis clearly stated. RICS also notes the Code is under review and advises using the Code and/or IPMS as appropriate, with the basis documented.
IPMS: Residential Buildings where the instruction requires it. For example, IPMS 2 – Residential is measured to the Internal Dominant Face for external construction features (and otherwise to the finished surface).
If a client’s appointment uses a specific NSA definition or a project-specific rule set, we align to that and make the basis explicit in the deliverables.
We present it in a way that makes commercial review quick:
A single Excel schedule with unit references matching site numbering.
Side-by-side columns for Design/Theoretical NSA and As-built NSA, plus:
variance in m² and ft²
variance as a percentage (if requested)
a short notes field for any assumptions or access limits.
PDF plans for each unit so the schedule figure has a clear drawing reference.
This format keeps everything traceable, and it supports fast checking across large unit counts. RICS also stresses that the basis of measurement used should be documented, which is why we include it alongside the outputs.
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