As-built survey of a two-storey steel-framed building, Chrastava

A two-storey steel-framed building in the Dolní Chrastava cadastral area was captured by laser scanning and turned into a full as-built drawing set. The drawings cover 19 rooms on two above-ground floors, 1,478.27 m² of room area in total. A small masonry storage building on the same plot was documented separately, as a demolition drawing set.

The building sits on plot 143/2 in the Dolní Chrastava cadastral area. It has two above-ground floors, the ground floor at ±0.000, the upper floor at +3.615 and the parapet at +9.350 metres. The structure is a steel frame on a 6 by 6 metre grid, seven bays one way and three the other. The drawings mark the members as rolled sections, IPE 100 up to IPE 400 and HEB 400. Two types of roof truss span the building, both with steel cable diagonals. The brief was an as-built survey, not a design.

Laser scanning ran in two campaigns, the second of them dated directly in the scan file names, 21 and 24 July 2026. The individual scans were registered and cleaned into a single point cloud. A topographic and detail survey added the surrounding site, producing a contour plan with spot heights and mapped hard surface edges, fences, manholes, trees and overhead power lines. A Revit model was built from the point cloud, and the drawings and schedules were generated from that model.

The as-built set runs to six sheets: a title sheet, floor plans of both levels at 1:100, framing layouts of the floor structures above each level, and a sections sheet that also carries both roof truss types. The floor plans give the number and area of all 19 rooms, from a 4.62 m² washroom up to two large open floors of 415.53 m² and 581.95 m². The client received the drawings in PDF and DWG, a merged PDF of the whole set and the model exported to IFC 2x3. The storage building has its own set with a plan, a section, three elevations and quantity schedules covering masonry, floor, roof, window, door and gutter.

Project challenges

A steel structure is both the easiest and the trickiest thing to record in an as-built survey. A point cloud captures the shape and position of a beam very precisely, but it does not reliably tell you which section it is, because the distinguishing details fall below the point spacing. Some beams also sit inside walls, where the scanner sees nothing at all. Both limits are stated as notes on the drawings, so that whoever designs from them later does not have to guess. An as-built survey of this type is non-destructive, with no opening up of the structure, so hidden build-ups appear only as far as they were visible. The second point is that two different documentation types met on one plot. The main building was recorded as an as-built survey, the neighbouring store as a demolition drawing set, and each follows a different logic, scale and content.

Project outputs

• Floor plans of the ground and upper floor at 1:100
• Framing layouts of the floor structures above both levels, with steel section marks
• Sections A-A' and B-B' with both roof truss types and the floor and roof build-ups
• Title sheet and a merged PDF of the full six-sheet set
• The complete drawing set in both PDF and DWG
• The building model exported to IFC 2x3
• Topographic and detail survey in DWG and DXF, site plan at 1:500
• Demolition drawing set for the store, plan and section at 1:50, three elevations at 1:50 and quantity schedules