1. Electrical was underestimated
Electrical rough-in ran roughly $5,000 over budget once the upstairs upgrade scope was confirmed mid-build. The original quote covered the ground floor only and assumed the upstairs board was adequate. It wasn't. Assessing the upstairs board and tail-end load before quoting the ground floor work would have caught the cost before it became a variation.
2. Window selection was left too late
Brisbane window lead times move, so leaving the glazing specs late let prices rise and pushed the weatherproofing target back. A written window quote secured before the slab is ready is a small piece of admin that prevents a multi-week delay.
3. The engineering variations were not pre-staged
A slab variation for deeper shale in one corner cost roughly $2,200 and added engineering time. The geotech had already flagged variability in the ground. Pricing a variation envelope into the original concrete quote would have avoided discovering the cost on pour day.
4. Sequencing: insulation before fit-off
On a build-under, insulation and plaster have to be signed off before the electrician and plumber return for fit-off. The trades were booked a day early and sat idle. A clearer read of the inspection hold-point sequence would have saved that day.
5. The decision worth reconsidering
Polished concrete was chosen for the lower-level floor, and it performs well. The slab finishing process needed a longer cure window than had been allowed, so it pushed the downstream trades back. See What we'd do differently for the longer list.
Where the figures came from
Every figure above comes from the 2018-2020 Coorparoo project. Use them as a directional sense-check alongside your own current quotes. See the full breakdown.
