What is an as-built plan?

Quick answer: An as-built plan is a measured drawing of a building as it actually exists today, rather than as it was originally designed. It records real dimensions, real wall positions, real ceiling heights and the changes made during construction or during later remodels. It is produced by going to the building and measuring it, and it is the starting point for any renovation, permit application, lease plan or sale of an existing property.

The difference between designed and built

Every building is drawn before it is built, and every building changes while it is being built. A wall moves four inches to clear a duct. A door gets relocated because the stair landing came out differently. A mechanical chase gets widened. None of that is a failure. It is construction.

The design drawings, the ones stamped and permitted, show the intention. The as-built plan shows the result. When those two disagree, and they almost always disagree somewhere, the as-built is the one you can rely on, because it was measured off the building rather than drawn before it existed.

That is the whole concept. Everything else is about how the measurement gets done and what the drawing has to contain.

What an as-built plan contains

• Floor plans at real measured dimensions, wall by wall, with openings located where they actually are.
• Wall thicknesses, which matter more than people expect, because usable area depends on them.
• Ceiling heights, including where they drop for ducts or structure. A single number for a floor is usually a lie.
• Doors and windows with real sizes, swings and head heights.
• Structure, at least the columns and bearing walls you can see or confirm, because those decide what a renovation can move.
• Visible mechanical, electrical and plumbing, to the level the project needs. Panels, risers, fixtures, exposed ducts.
• Stairs, elevators and shafts, which are the hardest things to move and so the most important to locate exactly.
• A dimension chain that closes. Each run of dimensions should add up to the overall. This sounds obvious and it is the main quality check.

Depending on the project the set may also include elevations, sections, a roof plan, a reflected ceiling plan and a site plan. The scope is set by what decision the drawings have to support.

How an as-built is actually produced

1. Whatever documentation exists is collected

Old permit sets, a surveyor's plat, a lease exhibit, a previous tenant's drawings, even a real estate floor plan. None of it is trusted, all of it is useful, because it tells you what to go look at.

2. The building gets measured

This is the part that cannot be skipped and cannot be done remotely. Someone walks the building with a laser distance meter, or scans it, and records real numbers. Rooms get measured in both directions and diagonally, because buildings are not square and the diagonal is what proves it.

3. The measurements are drawn

The field data becomes a clean CAD or Revit drawing at a real scale, with layers, dimensions and annotation that a permit office or a contractor will accept. See AutoCAD drafting services and Revit drafting services.

4. It is checked against itself

Dimension chains are added up. Overall building dimensions are compared to the survey. Floors are stacked to confirm the stairs and shafts line up vertically. Any contradiction gets resolved by going back and measuring again, not by splitting the difference.

Laser measuring versus 3D scanning

There are two ways to capture an existing building, and the right choice depends on complexity rather than on which sounds more advanced.

Hand measuring with a laser distance meter is fast, cheap and completely adequate for a house, an apartment, a small office or a retail space with orthogonal walls. A competent person can measure a three bedroom home in a morning.

Laser scanning, which produces a point cloud of millions of measured points, earns its cost when the building is large, geometrically irregular, historic, or when you need the ceiling plenum and the structure above it. It is also the right answer when the building is going to be modelled in 3D rather than only drawn in plan.

Paying for a scan of a square apartment is waste. Hand measuring a curved historic facade is a mistake. Match the method to the building.

What people use as-built plans for

Renovations and additions

The most common reason. You cannot design an addition against a plan that does not match the house, because the connection point is exactly where the error lives. A renovation drawn on bad as-builts produces change orders during construction, which is the expensive way to discover the measurement was wrong.

Permits on existing buildings

Most jurisdictions want existing conditions drawings alongside the proposed work, so the reviewer can see what is changing. If the existing plan is wrong, the review gets held up on something that has nothing to do with your design.

Leasing and area measurement

Rentable area is money. A lease exhibit drawn from an inaccurate plan is a dispute waiting for a tenant with a tape measure. Landlords and tenants both benefit from a measured set.

Buying or selling a property

Due diligence on an existing building means knowing what is actually there. Discrepancies between the recorded plans and the building turn up during diligence, and finding them before closing is better than after.

Facility management

Operators need to know where the shutoffs, panels and shafts are. A current plan set is the foundation of everything from cleaning contracts to emergency planning.

Insurance and legal matters

After damage, a measured record of what existed before is the basis for a claim. In litigation it is evidence, and evidence that was measured beats evidence that was remembered.

As-built, record drawing, and measured survey

The terms get used loosely and the differences occasionally matter.

A record drawing is the contractor's marked-up set at the end of a job, showing changes made during construction. It is produced from site knowledge, not from a fresh measurement, and its accuracy depends entirely on how diligently it was kept.

An as-built plan in the sense most clients mean is a drawing produced by measuring the building now, regardless of when it was built or what happened during construction.

A measured survey is the same thing with more emphasis on precision and often more scope, including levels and site context. In the United Kingdom this is the usual term.

If you are buying one, describe the use rather than the label. "I need existing conditions drawings accurate enough to permit a kitchen remodel" gets you a better quote than asking for an as-built.

What makes an as-built plan good or bad

• The dimensions close. Every chain adds to the overall. If they do not, something was assumed.
• The floors stack. Stairs, shafts and columns appear in the same place on every level.
• Nothing was assumed square. Older buildings are not. A plan drawn orthogonal when the building is not will fail at the first wall you open.
• The scope is stated. A good set says what was measured and what was not. "Ceiling plenum not accessed" is honest and useful. Silence is not.
• It is editable. A PDF is a picture. CAD or Revit files are what the next designer actually needs.
• Annotation is real. Room names, areas, materials where relevant, and a drawing title block that a permit office will accept.

The failure mode worth guarding against is a drawing that looks professional and is dimensionally wrong. It passes visual inspection and fails on site.

Common problems in existing buildings

Anyone who measures buildings for a living expects these, and you should expect them too, because they explain why a quote has contingency in it.

Walls are not parallel. A room that is 12 feet at one end and 12 feet 3 inches at the other is normal, and the drawing has to say so rather than average it.

Previous work was undocumented. Somebody enclosed a porch in 1987 without a permit. The plan has to record what is there, and then someone has to decide what to do about it.

Areas are inaccessible. A locked tenant space, a crawl space, a plenum above a hard ceiling. The honest answer is to note it as not surveyed, not to guess.

Structure is hidden. You can see a column. You often cannot see whether a wall is bearing. The drawing records what was observed and flags what has to be confirmed by opening a wall or by an engineer.

How to buy one well

Tell whoever is quoting four things: the building type and approximate square footage, what you are going to do with the drawings, what documentation you already have, and whether the whole building needs access or only part of it. Those four decide the price.

Then confirm the deliverable format. If an architect is going to design on top of this set, they need the native file. If the drawings are going to a permit office, confirm the sheet sizes and title block requirements before the work starts rather than after.

For scope and formats, see as-built drawings, and for drafting work generally, architectural drafting services or draftsman services. If you want the existing building visualised rather than only drawn, see 3D floor plans and architectural visualization.

How an as built set is actually produced

Knowing what an as built plan is helps less than knowing how it comes into existence, because the method is what determines whether you can trust the drawing.

It begins with a site visit, and the visit is the expensive part. Somebody walks the building with a laser distance meter, a tape for the short runs, and a printed sketch or an existing plan to mark up. Every room is measured wall to wall, every opening is located and sized, ceiling heights are taken in each space because they vary more than people expect, and structural elements are recorded where they can be seen.

The second rule of the visit is that the building has to close. A measured plan where the sum of the rooms does not match the overall external dimension is wrong somewhere, and the error has to be found on site rather than fudged in the drawing. This is why overall diagonals and external runs get measured even though no single room needs them: they are the check.

Services are recorded next, to the extent they are visible. Radiators, electrical outlets, switches, sanitary fittings, visible soil stacks, mechanical units and anything that constrains where a wall could move. What is behind a finished surface is recorded as unknown rather than guessed, and a careful set says so on the drawing.

Photographs follow, systematically rather than casually: every room from two corners, every elevation, every condition that looked unusual. The photographs are what let a question be answered three weeks later without a second visit, and a second visit is the single most avoidable cost in the whole exercise.

Only then does drawing start. The field notes are turned into a coordinated set in CAD, dimensions are closed, discrepancies are resolved or flagged, and the drawing is labelled with the date measured and the method used. That label matters: an as built set is a statement about a building on a particular day, and a building changes.

Common questions

What is an as-built plan in simple terms?

It is a drawing of a building as it actually exists today, produced by measuring the building, rather than a drawing of how it was originally designed.

How is an as-built different from the original construction drawings?

The construction drawings show the design intent before the building existed. The as-built shows the measured result, including every change made during construction and in later remodels.

Who needs an as-built plan?

Anyone renovating, adding to, permitting, leasing, buying, selling or managing an existing building. It is the base drawing that all of that work sits on.

How is an as-built plan produced?

Existing documentation is collected but not trusted, the building is measured on site with a laser meter or a 3D scanner, the measurements are drawn in CAD or Revit, and the dimension chains are checked until they close.

Do I need 3D laser scanning for an as-built?

Not usually. Hand measuring with a laser distance meter is adequate for houses, apartments, small offices and orthogonal retail. Scanning earns its cost on large, irregular or historic buildings, or when the building will be modelled in 3D.

What is the difference between an as-built and a record drawing?

A record drawing is the contractor marking up the set at the end of a job from site knowledge. An as-built is produced by measuring the building now, which is why it is more reliable.

How accurate should an as-built plan be?

Accurate enough that every dimension chain adds up to the overall dimension and the floors stack vertically. Anything looser will produce change orders when a wall gets opened.

Should I ask for CAD files or a PDF?

Ask for the native CAD or Revit file. A PDF is a picture and the next designer cannot build on it, which means paying to redraw what you already bought.

Frequently asked questions

What is an as-built plan in simple terms?

It is a drawing of a building as it actually exists today, produced by measuring the building, rather than a drawing of how it was originally designed.

How is an as-built different from the original construction drawings?

The construction drawings show the design intent before the building existed. The as-built shows the measured result, including every change made during construction and in later remodels.

Who needs an as-built plan?

Anyone renovating, adding to, permitting, leasing, buying, selling or managing an existing building. It is the base drawing that all of that work sits on.

How is an as-built plan produced?

Existing documentation is collected but not trusted, the building is measured on site with a laser meter or a 3D scanner, the measurements are drawn in CAD or Revit, and the dimension chains are checked until they close.

Do I need 3D laser scanning for an as-built?

Not usually. Hand measuring with a laser distance meter is adequate for houses, apartments, small offices and orthogonal retail. Scanning earns its cost on large, irregular or historic buildings, or when the building will be modelled in 3D.

What is the difference between an as-built and a record drawing?

A record drawing is the contractor marking up the set at the end of a job from site knowledge. An as-built is produced by measuring the building now, which is why it is more reliable.

How accurate should an as-built plan be?

Accurate enough that every dimension chain adds up to the overall dimension and the floors stack vertically. Anything looser will produce change orders when a wall gets opened.

Should I ask for CAD files or a PDF?

Ask for the native CAD or Revit file. A PDF is a picture and the next designer cannot build on it, which means paying to redraw what you already bought.