Commercial Fit-Out: Why CAT A Handover Needs a Measured Survey

If you are taking CAT A office space, commission the measured survey before CAT B design starts. Landlord drawings are usually good enough for legal/commercial context, but not good enough for partition, M&E, joinery, and furniture coordination.

The tenant who signs a lease on a commercial office floor receives, from the landlord or their agent, a set of "as-built" drawings purporting to show the CAT A shell: the ceiling grid, the raised floor extent, the perimeter trunking, the M&E distribution, the column positions, and the floor plate dimensions that the fit-out designer will use as the basis for the CAT B workplace scheme. These drawings were produced by the base-build contractor, reflect design intent rather than as-built reality, and carry an accuracy that degrades in direct proportion to how many value engineering decisions were made between detailed design and practical completion without corresponding drawing updates.

The fit-out designer who trusts these drawings without verification is designing a workplace within a spatial envelope that may not exist at the dimensions described. The partition that must terminate against a column will discover, at installation, that the column is 40mm from where the drawing showed it. The floor box grid that must align with the desk layout will discover that the raised floor zone is 30mm shallower in the south bay than the north. The meeting room whose AV installation requires a specific ceiling void depth will discover that the services above the ceiling tile are 80mm lower than the section drawing indicated, and the AV bracket no longer fits.

Why the "as-built" drawings are not as-built

The base-build contractor's CAD drawings represent what was designed to be built, updated (with varying degrees of completeness) to reflect what was actually constructed. The reality of a multi-storey commercial building delivered at pace under a design-and-build contract is that:

• Column positions are set out to tolerances (typically plus or minus 25mm from design grid), and the as-built drawing may or may not have been updated to reflect the as-set-out positions
• The structural slab level varies across the floor plate (construction tolerance, plus deflection under load), and the raised floor system accommodates this variation by adjusting pedestal heights, which means the finished floor level is not uniform even when it appears so
• Ceiling void depths vary with service routing, and the section drawing that shows "600mm clear void" represents a design minimum that is not achieved everywhere, particularly at service crossover points and near risers
• Core walls and lift shaft positions may have deviated from design grid during construction, and the usable floor plate area is consequently smaller or larger than the drawing shows in specific zones

None of these variations represent defects. They are normal construction tolerances. But they are tolerances that the fit-out designer needs to know about before they commit to a layout that assumes the building conforms exactly to a drawing that was last updated six months before practical completion.

What a measured survey captures at CAT A handover

A laser scan survey of the CAT A shell captures the floor plate as it actually exists at the point of tenant handover:

Column positions and dimensions. The actual position of every column on the floor plate, measured to within a few millimetres of its true location. If the columns deviate from the design grid (and on any floor plate longer than 30 metres, some will), the fit-out designer knows this before they draw the first partition.

Floor levels. The actual level of the raised floor surface across the entire plate, revealing any variation in floor flatness. For open-plan areas this rarely matters, but for rooms where a sliding partition meets the floor, or where bespoke joinery must sit level against a floor that is not, this data prevents installation-stage surprises.

Ceiling grid and void depths. The position of the ceiling tile grid, the level of the ceiling surface, and (where tiles can be lifted for observation) the available void depth at representative positions. The AV consultant, M&E designer, and lighting designer all need this information, and none of them want to discover it by sending a technician with a tape measure to forty individual ceiling tile locations.

Perimeter conditions. The exact position and configuration of perimeter trunking, window mullion spacing, sill heights, and the relationship between the curtain wall module and the structural grid. These dimensions determine where desking can terminate, where blinds can be mounted, and how the partition layout relates to the building envelope.

Core dimensions and door positions. The actual width of core doors (which may differ from the fire strategy drawing), the usable corridor width, and the spatial relationship between the core and the floor plate that determines how the fit-out circulation connects to the base-build circulation.

The CAD deliverable (what the fit-out designer receives)

The survey is delivered as a CAD floor plan (DWG) at 1:50 or 1:100, showing the ceiling grid, column grid, raised floor extent, core layout, and perimeter configuration as measured. This becomes the fit-out designer's base plan: the drawing they open on day one of the design process and use as the spatial framework for every subsequent decision.

The point cloud from which the plan was extracted persists as a three-dimensional reference. When the M&E consultant needs to verify a void depth at a specific location, or the joinery manufacturer needs a reveal dimension at a specific column, the information exists in the cloud and can be extracted without a return to site.

What to Expect: As-Built Drawings vs. Reality

The programme argument

A commercial fit-out programme is typically measured in weeks, not months. The design period is compressed. The procurement period overlaps with design. The construction period is short and intolerant of delays. In this context, discovering at week 6 of a 12-week programme that the base-build drawings are wrong (and that the partition layout must be revised, the furniture order amended, and the M&E coordination checked against actual void depths) is not a minor inconvenience. It is a programme compression that manifests as overtime, premium procurement, and the specific variety of stress that fit-out project managers produce when explaining to their client why the furniture will not arrive on the revised completion date.

The survey takes one to two days of scanning and one to two days of processing. On a fit-out programme where the design period is four to six weeks, commissioning the survey in Week 0 (immediately upon lease completion or access for survey) and receiving it in Week 1 gives the designer five weeks of productive work from an accurate base. Commissioning it in Week 3 (because someone assumed the landlord's drawings were adequate) gives the designer three weeks, plus the time lost verifying and revising whatever was designed in Weeks 1 and 2 against the drawings that turned out to be wrong.

The multi-floor efficiency

For tenants taking multiple floors in the same building (which is common for corporate occupiers), a single survey commission captures all floors in a coordinated dataset. The consistency between floors (which the base-build drawings may not guarantee, if different subcontractors completed different levels) allows the fit-out designer to identify where the building repeats and where it does not, and to adjust the fit-out design accordingly without discovering at construction stage that the ceiling grid on floor 3 is offset 150mm from the identical grid on floor 5.

The cost relative to the fit-out budget

A measured building survey of a single commercial floor plate (say, 1,000 to 2,000 square metres) typically costs between £2,000 and £4,000 (an indicative baseline based on standard industry parameters). The fit-out cost for the same floor is typically £800,000 to £2,000,000. The survey represents 0.1% to 0.5% of the fit-out budget, and its purpose is to prevent the spatial errors that generate the variation orders, the abortive work, and the programme delays whose cost dwarfs the survey by orders of magnitude.

The fit-out contractor who receives a tender package based on verified survey data can price with confidence: partitions measured to actual column positions, joinery dimensioned to actual reveals, services designed to actual void depths. The contractor who receives a tender package based on unverified base-build drawings prices contingency into every measured item, because they know from experience that the building will not be where the drawing says it is, and the first three weeks of construction will be spent discovering exactly where the discrepancies lie and who pays for resolving them.

That question (who pays?) is easier to answer when the survey exists. It is the landlord's building. It is the tenant's fit-out. And the measured survey, commissioned at the boundary between the two, defines where one ends and the other begins with the precision that prevents the argument from arising.

Frequently Asked Questions (FAQ)

Why aren't landlord 'as-built' drawings sufficient for a CAT B fit-out? Base-build drawings represent what was designed to be built, updated loosely during construction. They do not accurately capture the compounding construction tolerances (like column drift and slab deflection) that dictate whether your fit-out design will actually fit.

What exactly does a CAT A handover survey capture? It captures the precise floor plate as it exists: true column dimensions, actual floor flatness, ceiling void depths, perimeter conditions, and core dimensions, allowing you to design against reality rather than assumptions.

Who should pay for the survey: the landlord or the tenant? The tenant typically commissions it to protect their fit-out programme. However, the survey explicitly defines the boundary between the landlord's building and the tenant's works, preventing costly disputes over spatial discrepancies later.