Commercial As-Built Floor Plans for Existing Buildings

Quick answer: A commercial as-built floor plan is a measured drawing of a building as it exists now, not as it was designed. It is produced by surveying the building, then drawing what the survey found, and the deliverable is normally a dimensioned plan per floor in DWG and PDF with an area schedule. The variables that decide cost and programme are access to occupied space, how much of the ceiling void and services you need recorded, and the tolerance you can live with.

Why the drawings you already have are wrong

Almost every commercial building holds a drawer of drawings that do not match it. This is normal rather than negligent, and there are three reasons.

The design drawings describe the intent at the time of the tender. What was built differed, as it always does, and the record of those differences lives in site instructions that nobody consolidated.

Then came the fit outs. A commercial building of any age has been subdivided, reconfigured and re-let, usually several times, and the tenant works were drawn by whoever the tenant used. Those drawings describe one floor at one moment, in somebody else's conventions, and were never merged back into a building set.

Finally the building itself moved. Structures settle, openings get cut, risers get taken, and a wall shown as a line on a 1980s drawing is now a line plus a boxing plus a riser nobody recorded.

So the practical question is not whether your drawings are wrong. It is how wrong, and whether the decision you are about to make can survive the difference. See what an as-built plan is and as-built drawings versus record drawings.

What a commercial set normally contains

• A floor plan per level, dimensioned, with structure, partitions, doors, windows, columns, cores, risers and vertical circulation shown.
• An area schedule. On commercial work this is frequently the point of the exercise. State the measurement standard being used, because gross internal area, net internal area and the various leasing codes give different numbers from the same building, and a figure without a named standard is a liability rather than information.
• Reflected ceiling plans, where lighting, grid and ceiling heights matter to the next decision.
• Sections and elevations, usually fewer than on a design project. One section per core and per level change often does the job.
• Core and riser details, because the risers determine what a future fit out can and cannot do, and they are the thing least reliably shown on old drawings.
• Services, if asked. Visible services recorded as located is one scope. Services above a sealed ceiling is a different and much larger one.

Decide the services question explicitly before the survey, because it changes the access requirement and therefore the programme more than anything else on the list. For the full checklist see the as-built deliverable checklist.

Access is the real constraint

On an empty building the survey is straightforward. On a trading building it is a logistics exercise, and the cost sits in the logistics rather than the measuring.

Tenanted floors need notice, usually a tenant representative present, and often a time window that is nobody's first choice. A retail unit may only be accessible before opening. A data room, a dealing floor or a clinical space may be off limits entirely, and the honest answer then is to record it as not surveyed rather than to interpolate.

Plant rooms and roofs need a permit and a competent escort. Ceiling voids need somebody to lift tiles, which in an occupied office means a route agreed in advance and a limit on how many tiles come down in one morning.

The single most useful thing a client can do is produce an access schedule before anybody is priced: which floors, which hours, who holds the key, who must be present. A survey priced against a real access schedule lands on programme. A survey priced against an optimistic one does not, and the overrun is not the surveyor's fault.

Tolerance, stated honestly

Precision costs money, and it is possible to buy far more of it than the decision needs. Three bands cover most commercial work.

For space planning, lease plans and area schedules, a tolerance of roughly 25 to 50 millimetres on overall dimensions is normal and entirely adequate. You are deciding how many desks fit, not where a steel connection goes.

For fit out design and joinery, tighter work is justified in the zones where something has to be made to fit. Specify the tight zones rather than tightening the whole building, which is the expensive mistake.

For structural intervention, facade replacement or anything prefabricated, you want a survey done to a stated accuracy with a control network behind it, and probably a point cloud. See drafting accuracy and tolerance standards and, where scanning is the right tool, scan to BIM.

Whatever band applies, insist the tolerance is written on the drawing. A plan with no stated tolerance will eventually be used for something it cannot carry, by somebody who was not in the room when it was commissioned.

Plans, or a model

For many commercial purposes flat plans are the correct answer and a model is money spent on nothing. Leasing, area schedules, compliance, space planning and insurance records all live comfortably in 2D.

A model earns its cost when the building is going to be worked on repeatedly, when several disciplines need to coordinate inside it, or when the information attached to the objects matters. A landlord planning a decade of rolling refurbishment has a real case. A landlord who needs a lease plan next week does not.

The middle path that works well in practice is to produce good flat plans now, and build the model later for the floors that get worked on, using the survey information already captured. See CAD drafting versus BIM modelling and BIM modelling for smaller practices.

What drives the price

Floor area matters less than people expect. What matters is the number of separately accessible spaces, how repetitive the floors are, whether ceilings and voids are in scope, the tolerance band, and how much of the building is occupied during the survey.

A warehouse of 100,000 square feet is a quick job. A 30,000 square foot office subdivided into forty tenancies with individually arranged access is not, and the second will cost more despite being a third of the size.

Rendimension scopes as-built work after reviewing what exists and what access looks like, which is why there is no square foot rate on the site. The published figures on the 3D rendering cost page cover visualization deliverables, where ranges are stable: 3D floor plans or site plans run $750 to $2,500 and upwards per floor or site. Measured survey and as-built drafting is quoted against the building, because the same area can mean a week or two months. For how the variables behave see as-built drawings cost and what drives the price.

How to commission it well

Four things, written down, prevent nearly every problem.

State the purpose. Leasing, fit out, refurbishment, compliance or disposal. The purpose sets the tolerance, the level of detail and the output format, and a supplier who is not told the purpose has to guess and will guess cheaply.

State the measurement standard for areas, by name.

Produce the access schedule before pricing.

Agree the file deliverables: software and version, layer standard, whether PDF is issued alongside DWG, and who owns the files afterwards. See drafting deliverable formats explained, and for the wider service as-built drawings and architectural drafting services. Where the only record is an old paper set, converting old plans to CAD is a different and cheaper exercise, and the two are often confused.

The honest summary

Commercial as-built floor plans are not a difficult product. They become expensive and slow for one reason, which is access to space that other people are using, and that reason is manageable if it is faced before the job is priced rather than discovered during it.

Say what the drawings are for, name the area standard, write the tolerance on the sheet, and schedule the access honestly. Do that and you end up with a set somebody can rely on in five years, which is the only test that matters.

Keeping the set alive afterwards

A set of as-built plans is accurate on the day it is issued and slightly wrong a year later, because buildings keep changing. The practices that get value out of this work for a decade do one small thing: they make somebody responsible for updating the set when a fit out completes, and they require the incoming tenant drawings in the same software, layer standard and origin as the building set.

That second requirement costs the landlord nothing and is the whole difference between a building set that stays usable and one that drifts back into a drawer of incompatible files. Write it into the fit out guide rather than asking for it afterwards, because afterwards the consultant has already been paid and has no reason to redraw anything. See CAD drafting for permit drawings and choosing a drafting partner remote or local.

Common questions

What is a commercial as-built floor plan?

A measured drawing of a commercial building as it currently exists, produced by surveying the building rather than by reusing design drawings. It normally covers structure, partitions, doors, cores, risers and circulation per floor, with an area schedule, issued as DWG and PDF.

Why do my existing drawings not match the building?

Three reasons stack up: the design set described intent rather than what was built, successive tenant fit outs were drawn by different people and never merged back, and the building itself has had openings cut and risers taken since. The question is how wrong they are, not whether.

What should the area schedule say?

It must name the measurement standard used. Gross internal area, net internal area and the various leasing codes produce different numbers from the same building, so a figure without a named standard is a liability rather than information, especially where rent depends on it.

How is an occupied building surveyed?

With an access schedule agreed before pricing: which floors, which hours, who holds the key and who must be present. Tenanted space needs notice and usually an escort, plant rooms need permits, and ceiling voids need an agreed tile lifting route. Space that cannot be entered is recorded as not surveyed.

What tolerance do I need?

For leasing, area schedules and space planning, roughly 25 to 50 millimetres on overall dimensions is normal and adequate. For joinery and fit out, specify tighter work only in the zones where something must be made to fit. For structural or prefabricated work, commission a stated accuracy with a control network.

Should I buy flat plans or a BIM model?

Flat plans for leasing, compliance, insurance records and space planning. A model when the building will be worked on repeatedly, when several disciplines coordinate inside it, or when object data matters. A practical middle path is good plans now and a model later for the floors actually being refurbished.

What drives the cost of commercial as-built work?

The number of separately accessible spaces, floor repetition, whether ceilings and service voids are in scope, the tolerance band, and how much of the building is occupied. A large open warehouse is quick; a smaller office split into forty tenancies with individual access arrangements is not.

How do I write a brief that will not go wrong?

State the purpose of the drawings, name the area measurement standard, produce an honest access schedule before anybody is priced, and agree the file deliverables including software version, layer standard and ownership. Those four items prevent most disputes on this kind of work.

Frequently asked questions

What is a commercial as-built floor plan?

A measured drawing of a commercial building as it currently exists, produced by surveying the building rather than by reusing design drawings. It normally covers structure, partitions, doors, cores, risers and circulation per floor, with an area schedule, issued as DWG and PDF.

Why do my existing drawings not match the building?

Three reasons stack up: the design set described intent rather than what was built, successive tenant fit outs were drawn by different people and never merged back, and the building itself has had openings cut and risers taken since. The question is how wrong they are, not whether.

What should the area schedule say?

It must name the measurement standard used. Gross internal area, net internal area and the various leasing codes produce different numbers from the same building, so a figure without a named standard is a liability rather than information, especially where rent depends on it.

How is an occupied building surveyed?

With an access schedule agreed before pricing: which floors, which hours, who holds the key and who must be present. Tenanted space needs notice and usually an escort, plant rooms need permits, and ceiling voids need an agreed tile lifting route. Space that cannot be entered is recorded as not surveyed.

What tolerance do I need?

For leasing, area schedules and space planning, roughly 25 to 50 millimetres on overall dimensions is normal and adequate. For joinery and fit out, specify tighter work only in the zones where something must be made to fit. For structural or prefabricated work, commission a stated accuracy with a control network.

Should I buy flat plans or a BIM model?

Flat plans for leasing, compliance, insurance records and space planning. A model when the building will be worked on repeatedly, when several disciplines coordinate inside it, or when object data matters. A practical middle path is good plans now and a model later for the floors actually being refurbished.

What drives the cost of commercial as-built work?

The number of separately accessible spaces, floor repetition, whether ceilings and service voids are in scope, the tolerance band, and how much of the building is occupied. A large open warehouse is quick; a smaller office split into forty tenancies with individual access arrangements is not.

How do I write a brief that will not go wrong?

State the purpose of the drawings, name the area measurement standard, produce an honest access schedule before anybody is priced, and agree the file deliverables including software version, layer standard and ownership. Those four items prevent most disputes on this kind of work.