ServicesScan-to-CAD

As-Built Drawings and Surveys from 3D Laser Scanning

An as-built drawing shows a building as it stands today. The design set from twenty years ago shows where the walls were meant to go; the as-built shows where they are. We produce as-built drawings and surveys for existing buildings in every US state. The site is laser scanned, the scans are registered into one point cloud, and the drawings are traced against that cloud. You get floor plans, reflected ceiling plans, elevations and sections in DWG and PDF, with the point cloud as the measured record behind them.

What an as-built set contains

Most sets are ordered for a decision: a tenant improvement, a renovation permit, a lease exhibit, a facility with no drawings at all. The sheets follow from the decision, so the first thing we agree on is the list of sheets and what each one has to show. The usual as-built documentation package looks like this.

Deliverable	What it shows	Format
Floor plans	Walls, doors, windows, columns, stairs, fixed equipment, room names and areas	DWG, PDF
Reflected ceiling plans	Ceiling heights and grids, lights, diffusers, sprinkler heads, soffits	DWG, PDF
Interior and exterior elevations	Facades, storefronts, wall heights, openings, finish lines	DWG, PDF
Building sections	Floor-to-floor heights, slab and roof structure, ceiling cavities	DWG, PDF
Roof and site plans	Footprint, roof penetrations and equipment, paving and curbs	DWG, PDF
Registered point cloud	The scan the sheets are traced from	E57, RCP/RCS

A 2D set is the usual order, and the cloud comes with it in E57, the ASTM exchange format for 3D imaging data, and in RCP/RCS for Revit. When the project goes on to design in Revit, the same point cloud becomes a 3D as-built model instead of the drawings or on top of them, delivered as a Revit, IFC or ArchiCAD file; that work is described on the Scan-to-BIM page. As-builts of the mechanical, electrical and plumbing systems above the ceiling are a separate scope, scanned with the ceiling tiles lifted where they can be lifted, and belong to MEP BIM and drafting.

A set does not contain what the scanner cannot see, which means hidden framing, buried utilities and anything inside a wall. Those can be drawn from existing documents or from openings made for the survey, and the sheet then says which lines were measured and which were not.

The as-built survey: 3D laser scanning on site

The field work is a terrestrial laser scan, which is what makes this an existing conditions survey rather than a redraw of old documents. A scanner of the Trimble X7 class takes one station in two to seven minutes without images, depending on the point density, measures up to 500,000 points a second and holds a 3D point accuracy of 2.4 mm at 10 m and 3.5 mm at 20 m (one standard deviation) by its datasheet. A house takes a few dozen stations, and a commercial floor with a dropped ceiling and a crowded plenum takes more, because the scanner only measures what it can see: every room, closet or shaft that has to appear on a sheet needs a station with a view of it. The stations are registered to each other scan to scan, without targets on the walls, and the registration report, with the average error per station and the overlap between scans, is part of the delivery. Occupied spaces are fine. The scanner stands on a tripod and works around people and furniture, although furniture hides floor and wall lines, so a room cleared before the visit needs fewer stations and less drafting time. Our site preparation checklist lists what to settle before the visit.

A tape survey records the dimensions someone decided to take on the day. A scan records everything in line of sight, so a question that comes up a month later, the height of a window head or the offset of a column from the grid, is answered from the cloud without a second visit. The scanning itself, with the file formats and the registration, is described on the 3D laser scanning page; for choosing between a point cloud, a drawing set and a model, see the guide to existing conditions documentation for renovation.

The accuracy you can specify

A scope needs an accuracy number, and the U.S. Institute of Building Documentation publishes the standard that supplies one: the Level of Accuracy (LOA) Specification, now in version 3.1. It defines five levels from LOA10 to LOA50. In the USIBD guide to the specification, LOA10 means a deviation of up to 5 cm, LOA20 between 5 cm and 15 mm, LOA30 between 15 mm and 5 mm, LOA40 between 5 mm and 1 mm, and LOA50 under 1 mm, each stated at the 95 percent confidence level (two standard deviations). A higher level than the one specified is presumed acceptable.

The specification separates measured accuracy, the standard deviation of the field measurements themselves, from represented accuracy, the standard deviation of the line work or model drawn from them. A cloud can be measured to LOA40 while the plan drawn from it is represented at LOA30, because a wall that leans 8 mm over its height is still drawn as one straight line. A typical renovation or tenant set from us is drawn to LOA30; a facade restoration or a millwork package can ask for LOA40 line work. The quote names the level for each sheet.

LOA describes how closely the measurements and the drawing match the building, whereas the BIMForum Level of Development (LOD) Specification describes how far a model element is developed. Its LOD 500, the level for existing conditions, says the accuracy "shall be noted or attached to the Model Element", and BIMForum recommends the USIBD LOA for that. A scope that asks for "LOD 300 as-builts" therefore still needs an LOA next to it.

As-built, record and measured drawings

Three different documents get called as-builts on job sites. The contractor's as-built is the design set marked up in the field with the changes made during construction. The record drawing is the architect's clean set compiled from those markups at the end of the job. A measured drawing is drawn from measurements of the standing building, with no design set behind it.

What we deliver is the third kind, and it is the one to order when the design set is missing, out of date or not trusted: the drawing is traced from a scan of the building, so it does not inherit the errors of the set it would otherwise be marked up on. When a current record set exists and is trusted, a scan is still a quick check before a permit submission: the cloud is overlaid on the drawings and the set is corrected where the building differs, which costs less than redrawing. The tenant improvement guide shows what a landlord's old set usually misses.

Price and time

Price follows the area, the number of sheets and how cluttered the space is. Typical ranges from recent projects: a house or an apartment, scanned and drawn or modeled, $2,000 to $4,500; interiors with facades and the site, $2,500 to $5,000; an office or a commercial floor, $3,000 to $9,000. Large buildings run from $12,000 and are quoted on their own. A registered point cloud alone, without drawings, starts at about $1,200. The exact price comes in a quote within one business day of your sending the address, the sheet list and any existing drawings. The cost of 3D laser scanning post explains what moves the price.

The scan is scheduled as soon as the project needs it, often within days of the order, and usually takes a day for a house or a floor. The drawings usually follow in two to three weeks for a house and in four to eight weeks for a commercial floor or a whole building, depending on the sheet count. We scan in all 50 states.

Frequently asked questions about as-built drawings

What are as-built drawings?

Drawings of a building as it exists, with the dimensions and positions measured on site rather than taken from the original design set. In our work they are traced from a registered laser scan and delivered as floor plans, reflected ceiling plans, elevations and sections in DWG and PDF, with the point cloud included.

How much do as-built drawings cost?

A house or an apartment usually costs $2,000 to $4,500, interiors with facades and the site $2,500 to $5,000, and an office or a commercial floor $3,000 to $9,000. Large buildings are quoted on their own, from $12,000. The quote arrives within one business day.

How long does an as-built survey take?

The scan is scheduled as soon as the project needs it, often within days of the order, and usually takes a day for a house or a floor. Drawings take two to three weeks for a house and four to eight weeks for a commercial floor or a whole building, depending on how many sheets are in the set.

What do you need from us before the scan?

The address, the list of sheets you need, any existing drawings, and access: who opens the doors, which rooms are locked, whether ceiling tiles may be lifted, and whether an escort is required. The site preparation checklist covers the rest.

Can we order the point cloud only?

Yes. A registered point cloud in E57 and RCP/RCS, with the registration report and no drawings, starts at about $1,200. Your own team can then draw or model from it.

What accuracy do you work to?

Accuracy is stated in USIBD Level of Accuracy terms in the quote. A typical renovation set is drawn to LOA30, which means the line work deviates from the building by no more than 15 mm, and usually less than that, at the 95 percent confidence level. Tighter line work can be specified for facade restoration or millwork.

Do you cover my state?

Yes. We scan in every US state. The coverage page explains how a visit is scheduled.