Common Building Mistakes: What Good Construction Looks Like

Building defects are not rare. They show up in the majority of inspections, including new builds from volume builders with good reputations. Understanding what good looks like in each category helps you ask the right questions, interpret your inspection report, and know when something needs attention.

This guide works through eight defect categories drawn from the SURE Building Inspections defect database. For each one, it describes what correct construction practice produces, and where the common gaps are.

Structural: frames and connections done right

A structurally sound frame is straight, plumb, correctly braced, and connected according to the engineer’s specification and AS 1684.2. What good looks like:

• Wall frames plumb to within 3 mm over 3 m
• Diagonal bracing at the correct spacing for the wind classification, with metal strap or solid timber installed as specified
• Anchor bolts correctly positioned in the slab, with the right hold-down connectors at the base of each stud
• Ridge, hip, and valley connections fully nailed with the specified nail pattern
• Lintels over windows and doors sized for the opening span, as shown in the structural drawings

The most common structural finding at frame stage is incorrect or missing bracing. Volume builders work at pace and frames go up quickly. A wall segment that should have a diagonal brace but doesn’t is not visible once plasterboard is installed. That’s why the frame inspection happens before lining: to check what the plans require against what was built.

Related: frame inspection service and lock-up inspection.

Moisture: keeping water out of the building envelope

Water management starts at design and ends at maintenance. A well-built building envelope handles rain, wind-driven moisture, and rising damp through layers that work together: flashings, sarking, weep holes, drainage falls, and damp proof courses.

What good looks like:

• Flashings at window and door heads, sealed and lapped correctly so water runs away from the opening
• Weep holes in brick veneer at the base of walls and above openings, clear and unobstructed
• Sarking (foil or non-woven membrane) behind cladding, lapped and continuous
• Site fall away from the building perimeter: finished ground levels drain away, not toward the slab edge
• Roof valley flashings correctly formed with adequate width and no mortar blockages

Moisture ingress through the building envelope often takes months or years to show up internally. By the time a water stain appears on a plaster ceiling, the water has been sitting in the wall cavity or roof space for some time. The lock-up inspection is the right window to check envelope details, before scaffolding comes down and before internal linings make access difficult.

Termite: conditions that prevent establishment

Termite management in new construction is not just about treatment. It is about design and construction practices that reduce the conditions termites need to establish.

What good looks like:

• Termite management system installed according to AS 3660.1 and the manufacturer’s specification (physical barrier, chemical barrier, or reticulation as specified)
• No untreated timber-to-soil contact anywhere around the perimeter
• Weep holes clear (blocked weep holes increase moisture in the wall cavity)
• External landscaping and garden beds not piled against the external wall
• Subfloor ventilation adequate (where applicable) to prevent moisture accumulation

For new builds, the inspection check is whether the installed termite management system is consistent with what the specification and the authority approval require. For existing buildings, the inspection looks at conducive conditions alongside any evidence of activity.

Related: timber pest inspection.

Waterproofing: the most costly thing to fix after the fact

Wet area waterproofing is covered by AS 3740. The standard requires a continuous membrane, turned up to the correct height on walls, with correct lapping at junctions. What good looks like:

• Membrane continuous across the floor, turned up at least 150 mm on walls (more at shower hobs)
• Junction between floor and wall treated with reinforcing tape before membrane application
• Membrane extended to cover the full wet area floor, not just the shower base
• Shower hob correctly formed, with waterproofing applied over and around it
• Grout and tile adhesive applied to a properly cured, correctly prepared membrane

The pre-plaster (pre-lining) inspection is the only practical window to verify waterproofing before it is covered by tiles. Once tiling is complete, the membrane is not visible. If waterproofing fails after tiling, rectification requires full tile removal, membrane repair or replacement, and retiling. That cost is many times higher than the cost of a pre-plaster inspection.

Related: new build stage inspections guide.

Roofing: where long-term performance is set at installation

A roof that performs for decades is installed correctly the first time. What good looks like:

• Tiles correctly lapped, aligned, and bedded at the ridge and hips
• Metal roof sheeting fastened at the correct centres with the specified fastener type
• All penetrations (pipes, flashing saddles, skylights) fully flashed with no exposed gaps
• Valley flashings correctly formed and not mortar-blocked
• Gutters at the correct fall (minimum 1:500) with adequate overflow capacity
• Downpipes discharging to stormwater, not to grade

Roofing defects that are present at installation are most efficiently corrected while scaffolding is still on site. Once scaffolding is removed after lock-up, roof access requires separate scaffolding or swing stage equipment. The lock-up inspection captures these while correction is straightforward.

Related: lock-up inspection.

Drainage: surface water management

Stormwater mismanagement is one of the most common findings in both new builds and existing homes. What good looks like:

• Site falls away from the building on all sides (AS 3500 requires a minimum 50 mm fall across the first 1 m from the building)
• Surface drainage channels or soakwells sized for the catchment area
• Downpipes connected to stormwater infrastructure, not discharging to the ground adjacent to footings
• Retaining walls with weep holes and drainage aggregate behind them, where applicable

Drainage that works on a dry day but saturates the subfloor and footing zone during a wet season is a structural issue, not just a nuisance. Reactive clay slabs behave differently when the soil moisture changes. Getting drainage right at construction is straightforward; correcting it after landscaping is established is not.

Electrical: correct at installation means safe for the long term

A correctly installed electrical system in a new home gives you protection from the start. What good looks like:

• RCDs (residual current devices) installed on all power circuits and at least one lighting circuit, per AS 3000
• Switchboard correctly labelled, with no live terminations accessible
• Smoke alarms correctly positioned, hardwired to the grid, and interconnected as required by state legislation
• Cables secured and not in contact with insulation in the roof space in ways that cause overheating
• Switchboard location accessible and not blocked by subsequent construction

The pre-plaster inspection includes a visual check of electrical rough-in: conduit runs, switchboard position, and smoke alarm locations. A licensed electrician is required for electrical compliance certification. An independent building inspector is not an electrician, but they can flag obvious issues during the pre-plaster window when the rough-in is exposed.

Compliance: meeting code without assuming it

National Construction Code requirements cover dimensions, materials, and installation details across dozens of building elements. What good looks like:

• Balustrade heights correct for the application (1 m for decks over 1 m above ground, 1 m for stair balustrades)
• Safety glazing in locations specified by the NCC (adjacent to doors, low sills, wet areas)
• Ceiling heights meeting minimum requirements for habitable rooms
• Pool fencing compliant with state legislation: height, latch type, gate self-closing and self-latching mechanism all correct

Compliance items that are incorrect at practical completion are typically the builder’s obligation to rectify under the contract. Items that are not identified and documented at handover become warranty claims. Both are enforceable, but pre-handover rectification is faster and less adversarial than post-settlement warranty proceedings.

Related: handover inspection checklist.

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What an independent inspection gives you

Understanding what good construction looks like helps you engage with your inspection report. A report that documents correct bracing at the frame stage, or confirms waterproofing before tiling, or identifies a missing flashing at lock-up is giving you an objective record of the build’s condition at each point.

That record has value during construction (builder accountability), at handover (defect rectification), and after (warranty claims, future sale). The inspection is not a pass/fail event. It is documentation.

Book a stage inspection or call 1300 787 327 to discuss timing for your build.