Quick summary
- A point cloud is the measurement. The as-built drawing set is what your architect, engineer and contractor actually work from, so it has to be specified as carefully as the scan.
- A typical set is floor plans, reflected ceiling plans, exterior and interior elevations and building sections. Industrial jobs add equipment, tank and piping layouts.
- Agree four things before anyone drafts a line: which sheets, what gets drawn, how accurate the linework must be, and whose CAD standard it follows.
- Decide early whether walls are drawn as they are or squared up. It changes what the drawings can be used for.
- On a water treatment retrofit at a Dallas beverage plant, one as-built plan with internal elevations put the owner, the engineers and the contractors on the same set of drawings.
For how we scan and draft a building, see our as-built documentation service.
Why as-built drawings still matter when you have a point cloud
Laser scanning captures an existing building as millions of measured points. That data is complete, but almost nobody on a project team designs from a point cloud. Architects work in plans and elevations, engineers mark up sections, contractors price from sheets they can print, and permit reviewers expect drawings.
The point cloud is the evidence, the drawings are the answer
Think of the scan as the evidence and the drawing set as the answer to a specific question. “What is the clear height under the mezzanine?” “Will the new tank fit between these two columns?” “Where does this pipe rack actually run?” The drawings pull those answers out of the point cloud and put them on a sheet at a scale people can use.
Who uses the drawings
- Architects and designers use floor plans and elevations as the base for renovation and fit-out design.
- Engineers use sections and equipment layouts to check loads, routing and clearances.
- Contractors use them to price, plan demolition and set out new work.
- Owners and facility teams keep them as the record of what the building is today.
If you are not sure whether you need 2D drawings, a 3D model or both, our comparison of scan to CAD vs scan to BIM covers that decision. This post is about the drawing set itself.
What a laser-scanned as-built drawing set includes
The sheets below are the usual building blocks. Most projects need three or four of them, not all.
Floor plans
The core of almost every set. A floor plan is a horizontal cut through the building, usually about 1.2 m (4 ft) above the floor, showing walls, doors, windows, columns, stairs, fixed equipment and dimensions. Every level gets its own plan, including mezzanines and roofs where they matter.
Reflected ceiling plans
A reflected ceiling plan (RCP) shows what is overhead: ceiling heights and types, bulkheads, beams, lights, diffusers and sprinkler heads. For fit-outs and mechanical upgrades, the RCP often matters more than the floor plan.
Exterior elevations
Each face of the building drawn flat, with window and door openings, floor lines, parapets and roof heights. Elevations are what an architect needs for facade work, additions and most permit applications.
Interior elevations
Walls drawn from the inside, used where the wall itself is the work: kitchens, washrooms, lab benches, equipment walls and, on industrial jobs, the elevation of tanks and piping against a wall or structure.
Building sections
Vertical cuts through the building showing floor-to-floor heights, slab and roof thicknesses, and how levels relate. Sections are where hidden problems show up, like a floor that steps or a roof that sags.
Equipment, tank and piping layouts
Industrial plants need more than architecture. Plans and elevations of tanks, pumps, skids and pipe runs, with centrelines and elevations, are what engineers use to design tie-ins and retrofits. This is where a scan earns its cost, because this equipment is rarely on any existing drawing.
What gets drawn and what gets left off
A point cloud shows everything, including chairs, pallets, hoses and people. A good drawing set leaves most of that out. The only way to get the right set is to agree up front what is in scope.
Agree the level of detail
Say what should be drawn and at what size. Door swings and window mullions or just openings? Every conduit or only pipes over a certain diameter? Furniture or none? Written scope avoids a set that is either cluttered or missing the one thing you needed.
Tag the things you will schedule later
If windows, doors or equipment will be replaced, ask for them to be tagged on the drawings. Tags let your team build schedules and quantities from the as-built set instead of counting again on site.
Hidden conditions stay hidden
A laser scanner measures surfaces it can see. It does not see inside walls, under slabs or above closed ceilings. Where those areas matter, plan access (ceiling tiles out, panels open) before the scan, or accept that the drawings will show only what was visible. Honest drawing sets say so in a note.
How accurate the drawings are
There are two accuracies in any as-built job, and people often mix them up.
Scan accuracy vs drawing accuracy
The U.S. Institute of Building Documentation separates measured accuracy (how close the scan data is to the real building) from represented accuracy (how close the finished linework or model is). Its Level of Accuracy (LOA) Specification defines bands for both, at 95% confidence. For example, LOA30 is 5 to 15 mm (about 3/16 to 9/16 in) and LOA20 is 15 mm to 5 cm (about 9/16 to 2 in).
Drawings lose some accuracy compared to the scan, because drafting simplifies what it sees. Specify both numbers, not just the scanner’s spec sheet. For most renovation and fit-out drawings, LOA20 or LOA30 linework is plenty. Structural tie-ins and tight equipment installs may need tighter.
As-found or squared up
Real walls are not perfectly straight, plumb or square. You can ask for them to be drawn exactly as found, or cleaned up to straight lines and right angles within a tolerance.
- As-found is right when the variation matters: settling floors, out-of-plumb walls, columns off their gridlines.
- Squared up is easier to design from and fine when small deviations do not affect the work.
Either is valid. The problem is not saying which one you want and then being surprised by the result.
CAD standards and file formats
Whose template
If your office has a CAD standard, send it before drafting starts: layer names, title block, text styles, line weights and sheet sizes. Without one, most drafting teams follow the United States National CAD Standard, which includes the AIA CAD Layer Guidelines. Getting this right first saves a round of redrafting later.
DWG, PDF or Revit
AutoCAD DWG is the usual deliverable for 2D sets, with PDFs of the plotted sheets for anyone without CAD. If the project is moving into BIM, drawings can come from a Revit model instead, which keeps plans, elevations and sections coordinated.
Coordinates and north
Say whether drawings need to sit on a project grid or survey coordinates. If they do, the scan has to be tied to control on site, which is much easier to plan before the scan than to fix after.
Field note: a water treatment retrofit at a Dallas beverage plant
One of our industrial jobs in the Dallas area shows why the drawing set matters as much as the scan. The client is private, so no names. The plant produces soft drinks, and the owner was planning a retrofit of the water treatment area.
The job
Water treatment in a beverage plant is a dense space: tanks, filters, pumps and a lot of piping, most of it changed over the years without anyone updating the drawings. Before redesigning the area, the owner needed to know what was actually there and where.
What we drew
We scanned the area and produced an as-built floor plan that located the tanks and piping as they really sit, together with internal elevations showing the equipment and pipe runs at height. The goal was one set of drawings that described the water treatment area as it is today, not as it was first designed.
What it changed
With that set, the owner could sit down with the engineers and the contractors and work from the same information. Design, pricing and construction planning all started from the same measured drawings instead of each party checking the site on its own. On a retrofit inside a running plant, that shared starting point is most of the value.
Lessons for your own retrofit
- Decide who will use the drawings before scoping them. Engineers and contractors need different sheets than an owner’s facilities team.
- On industrial jobs, ask for elevations of equipment and piping, not just a floor plan. Plans alone hide what happens at height.
- Scan the whole area around the retrofit, not just the equipment being replaced. Tie-ins always reach further than expected.
Planning plant work in Texas? See 3D laser scanning in Dallas.
What drives the cost of an as-built drawing set
Scanning and drafting are usually priced as separate line items, and drafting is often a large share of the total. The main factors are:
- Number and type of sheets. Floor plans alone cost far less than a full set with RCPs, sections and interior elevations.
- Level of detail. Every extra element drawn is drafting time.
- Accuracy. Tighter represented accuracy means more careful drafting and checking.
- Building complexity. Industrial plants with piping and equipment take longer to draw than open warehouses.
- CAD standard. Working to a client template is normal, but a complex standard adds setup time.
If the drawings are for lease or sale, rentable area may also need to follow a BOMA standard.
Before you order as-built drawings: a checklist
- What decisions will the drawings support, and who will use them?
- Which sheets: plans, RCPs, elevations, sections, equipment layouts?
- What level of detail, and what gets left off?
- What represented accuracy (LOA band) do you need?
- As-found or squared up?
- Whose CAD standard, and which file formats?
- Project grid or survey coordinates?
- Any areas that need access opened up before the scan?
Send those answers with your request and you will get an accurate quote and a drawing set you can use on day one. Our as-built documentation service covers scanning and drafting in one scope.
Frequently asked questions
How accurate are as-built drawings from laser scanning?
The scan itself is typically accurate to a few millimetres. The drawings are slightly less accurate because drafting simplifies geometry. Most renovation and fit-out sets are specified at LOA20 or LOA30 under the USIBD Level of Accuracy Specification, which is 5 mm to 5 cm at 95% confidence.
What is the difference between as-built drawings and record drawings?
Record drawings are usually the contractor’s marked-up construction set, handed over at closeout. As-built drawings from a laser scan are measured from the building as it stands today, so they also capture changes made after construction.
Can I get both CAD drawings and a Revit model?
Yes. Drawings can be drafted directly in AutoCAD from the point cloud, or cut from a Revit model built from the scan. If you need both, building the model first keeps them consistent.
Do as-built drawings show what is inside walls or above ceilings?
No. A laser scanner only measures surfaces it can see. Open ceiling tiles and access panels before the scan if concealed services matter, and expect a note on the drawings for areas that could not be seen.
Which drawings do I need for a building permit?
It depends on the jurisdiction and the scope of work, so check with your architect or the building department. Most renovation permits need existing floor plans, and work that changes the exterior usually needs elevations too.
Measure first, then draw
The scan is the easy part to specify. The drawing set is where projects go wrong: the wrong sheets, the wrong level of detail, or linework squared up when the deviation was the point. Settle those questions before drafting starts, and the as-built set becomes the one document everyone on the project trusts.
