Building work rarely goes entirely to plan. What matters is catching issues early, understanding their implications, and getting them fixed correctly rather than bodging them and hoping.
Site Conditions Don't Always Match the Design Assumptions
Footing design is based on a soil classification derived from boreholes. Boreholes sample at a few points across the site. When excavation starts and the actual soil is exposed over the whole footprint, surprises are not uncommon:
- A layer of uncontrolled fill that the boreholes missed, or that was thinner or thicker than expected.
- Reactive clay that's more reactive than the classification predicted, or less reactive than feared.
- Rock closer to the surface than expected, making standard footing depths impractical.
- Groundwater appearing at depth when the site was expected to be dry.
What to do: Have an engineer inspect the excavation before concrete pours. Not to approve every detail, but to confirm that what's actually in the ground matches what the design assumed. If it doesn't, the design can be adjusted and re-issued rather than built wrong and fixed later.
Waterproofing Problems During Construction
Moisture is the enemy of new concrete and new homes. Before the roof is on and walls are closed in, the building has no weather protection:
- Rain gets into the slab edge and under concrete before it's cured. This can cause cracking and affects the long-term durability of steel reinforcement.
- Groundwater can pond against foundation walls during construction if site drainage isn't established.
- Mud and water get tracked onto the completed slab, kept wet by the enclosed building, and soften the concrete before it's fully cured.
- Plumbing and stormwater rough-ins can leak during testing and commissioning phases.
What to do: Good site drainage should be one of the first things completed, before concrete is poured. Guttering and temporary downpipes should direct water away immediately. Slab edges should be protected from water until curing is complete. Internal water systems should be tested and inspected before the building is enclosed.
Structural Inspection Points That Often Get Missed
Several moments in the build are critical inspection points. Missing them means defects get buried in the next stage:
Before Footing Concrete
Reinforcement placement, cover to the edge of the concrete, proper compaction of subgrade, and correct footing dimensions all have to be right before the concrete truck arrives. Once concrete is poured, these can't be checked or corrected.
Suspended Floor Drainage on a Sloping Site
Most Adelaide houses are slab-on-ground, but a sloping allotment (the Hills face zone, or a hillside suburb like Belair or Aldgate) often calls for a suspended floor on piers instead, with a ventilated sub-floor void underneath. The fall away from the dwelling, the sub-floor drainage and the vent openings all need checking before the floor frame closes the space off. A sub-floor that holds water is a termite and timber-durability problem for the life of the house, discovered only once the floor is sitting on top of it.
Framing Connections
Steel connections, hold-down fasteners, bracing bolts, and beam bearing details all need to be inspected before cladding covers them. Bolts in the wrong position or missing fasteners don't show once the walls are closed in.
Roof Framing and Bracing
Wind bracing in roof trusses, connection of trusses to walls, and adequacy of ridge and collar ties need to be right. Again: difficult or impossible to correct once cladding and ceiling are in place.
Common Framing Mistakes and What Causes Them
Construction-stage questions often trace back to a few recurring issues:
Beam Bearing Insufficient
A beam sitting on a top plate or a column with too little bearing length can settle into the support, especially if there's any movement in the foundation below. Specification calls for 150mm minimum. Often sees 75mm or less.
Fix: Before the beam is loaded (before floor joists or roof load), adjust the support to get adequate bearing. After loading, it's much harder.
Hold-Downs Missing or Positioned Incorrectly
Anchor bolts that tie walls to the footing, and tie-down fasteners that secure upper floors to lower ones, have specific placements. Wrong placement or missing fasteners mean the structure isn't actually connected as designed.
Fix: Identify the issue before subsequent framing is completed. Adding hold-downs mid-build is possible but expensive.
Bracing Inadequate or Incorrectly Detailed
Lateral bracing (wind bracing) in roofs and walls keeps the structure square and stable. If bracing is insufficient or the connections aren't detailed properly, the structure can rack under wind load.
Fix: Get it right the first time. Once the roof is on and ceilings are in, it's very difficult to add or improve bracing.
Working with Deviations and Variations
It's not unusual for the builder to encounter a situation where building exactly to the drawings isn't practical or economical. Maybe the footing level is slightly different. Maybe a column location moves by 100mm. Maybe available materials don't match the specification exactly.
The right approach: Tell the engineer. Describe the variation and the reason for it. The engineer can confirm whether it's acceptable as-is, requires a small adjustment, or genuinely can't be approved. Building to suit convenience and hoping for the best later is a gamble.
Post-Construction Issues: Identifying Cause
A few issues only show up after occupation:
- Cracking in plasterboard or concrete that appears weeks or months after construction.
- Water pooling or leaking into the sub-floor space that shows up in heavy rain.
- Movement or noise in floors or roof framing.
- Doors and windows that stick or bind, from movement in the frame.
Distinguishing between design issues, construction errors, and normal settlement is important for deciding whether remedial work is needed and what form it should take. Getting an engineer to look early beats waiting and hoping it stops.
The Site Inspection Checklist
If you're building, don't wait for problems. Arrange inspections at these key moments:
- Before excavation or clearing: confirm site conditions match design assumptions.
- After excavation, before footing concrete: check subgrade preparation and reinforcement.
- After footing concrete but before backfill: inspect bearing, defects, and embedded items.
- Before structural framing: confirm bearing surfaces and any required tie-downs.
- After major structural work before weatherproofing: inspect connections, bracing, and adequacy of support.
- Before occupancy: confirm all work matches the design and any approved variations.
This article is general information for builders, architects, and homeowners. It isn't advice for a specific project, and it doesn't replace engagement with your local building certifier or the supervising structural engineer for your job. Requirements and inspection points vary with local building codes and project specifications.