How to read a DA drawing set for estimating
Which sheets carry the numbers, what to measure first, and the traps in preliminary sets that quietly move a price by six figures.
Published 19 September 2026 - 9 min read
Start with the sheet list
A development application set from an Australian architect follows a predictable order: locality plan, existing / demolition plan, existing elevations, proposed site plan, floor plans per level, elevations, sections, calculations, 3D views, window schedules, shadow diagrams, subdivision plan, site analysis and construction management plan. Structural concept advice and civil / stormwater drawings usually arrive as separate sets from the engineer. Before measuring anything, list every sheet and mark which ones carry quantities. In a typical 20-sheet set only eight or nine do.
The site calculations table is your friend
Most DA site plans carry a site calculations table for council: site area, floor area per level, total gross floor area, floor space ratio and landscaped area. Those figures are calculated by the architect from the model and are the most reliable numbers in the set. Use them for gross floor area (painting, electrical points, waste, insurance), slab area (the ground floor line), suspended slab area (mezzanine and upper floors) and landscaping. Note what they exclude: garages often carry an allowance deduction, terraces and balconies are usually outside GFA, and voids are excluded from the upper floor.
Measure the envelope from plans and elevations together
External wall area is perimeter times height less openings. Take the perimeter from the figured dimensions on the floor plan (never scale a DA plan if a figure exists), the wall height from the section (floor level to ceiling level, plus parapet), and the openings from the window schedule. The schedule also tells you which openings are single or double glazed, louvre, sliding or fixed - the BASIX glazing table is usually the most specific place that information appears, and the difference between single and double glazed aluminium is roughly A$400 per square metre.
Read the structural notes as cost items
Concept advice from a structural engineer is written to the architect, but every note is a cost line: "raft slab bearing on rock" means rock excavation and a thinner slab; "block or Dincel retaining wall pending depth of rock" means a wall, tanking, subsoil drainage and a waterproofing risk; "270 mm brick cavity with internal load-bearing skin" is a different envelope rate to a framed and clad wall; "approximately 360 UB steel members to support planter" is a tonnage and a crane day. Isolated columns, portal frames and suspended slabs each pull the estimate away from a project-home benchmark.
Civil drawings tell you about water and dirt
The stormwater plan carries pit sizes and counts, pipe diameters and runs, grated drains, silt arrestors, rainwater tanks, easements and the connection point. Read the notes: "no OSD required" removes a detention tank; "sewer within 900 mm clearance zone" means footings must clear or bridge the Sydney Water asset; "all excavations near trees to be hand dug" is a labour rate multiplier. Sloping foreshore sites add inclinators, external stairs and retaining that never appear on the architectural set at all.
What a preliminary set does not tell you
DA sets are not for construction. Expect gaps: no reinforcement, no footing sizes, no internal finishes schedule, no joinery drawings, no electrical layout, indicative downpipes. Price these with allowances, say so in your assumptions, and turn each gap into a request for information. The client sees a professional who knows what moves the price, not a guess dressed up as a quote.
Where Build Design Solutions Cost fits
The AI estimator does exactly this reading for you - classifies every sheet, pulls the site calculations, reads the schedules and the structural and civil notes, and lists what is missing - then measures against a rate catalogue so every quantity has a basis and a page reference. Try it on your next set.