Scheduling Statutory Inspections on Your Gantt

Why statutory inspections must be on your Gantt, not just in a notebook

A statutory inspection is not a box-ticking interruption — it is a gate. Until the inspector signs off, the next phase of work cannot legally begin. Yet most Thai SME contractors keep their inspection dates in a notebook or a LINE message, not on the schedule. The result is predictable: the inspection is booked three days later than it should be, the inspector has no availability for another week, and the trade waiting on the result loses ten days on a task the schedule showed as clear. Treating inspections as schedule events, planned on the Gantt with proper predecessors, closes that gap before the project feels it.

Which inspections does a Thai construction project typically need?

The list depends on project type and size, but the common statutory gates are: the foundation and structural frame inspection by the local authority before filling or casting above; the MEP rough-in certification covering electrical conduit, plumbing, and air-conditioning before walls are plastered; crane inspection by a licensed engineer every three months for lifting equipment with a safe working load above three tonnes; a fire protection rough-in check on projects above a specified height; and the final occupancy and structural sign-off required before handover. Thailand's updated occupational safety notification effective July 2026 adds new requirements for hazard warning signs on sites — a small compliance task worth adding to the pre-inspection checklist.

How do you add inspections to a Gantt chart?

In SiteBoard's Gantt planning view, set each inspection as a milestone — a zero-duration event marking a single point in time. Give it a clear label, such as Structural frame inspection — local authority, so it cannot be confused with an internal review meeting. Then link the inspection as a predecessor to the first task of the phase it gates: the milestone must be marked complete before the dependent task can start. Add a preparation buffer of one to two working days immediately before the inspection milestone — time for the site supervisor to sweep for small deficiencies and confirm the inspector is still coming. This buffer has saved many a contractor from a failed inspection on a site that was 95% ready but missing a safety sign.

How far in advance should you book a statutory inspection?

For structural frame inspections with the local authority — the Tessaban or Bangkok Metropolitan Administration — three to five working days is a reliable minimum, but this can stretch to ten days at the start of a new quarter when bookings cluster. Crane inspections by a licensed engineer typically need at least one week's advance notice — there are fewer certified inspectors than there are cranes, and their calendars fill when multiple projects compete for the same experts. The right move is to add an inspection booking task on the Gantt seven to ten days before the inspection milestone, assigned to the project manager. Booking late is one of the most avoidable causes of inspection-related schedule slippage.

A worked example: three inspection gates on a 120-day townhouse project in Pathum Thani

Khun Somchai is managing a 120-day, two-storey townhouse project in Pathum Thani worth 3.2 million baht. He builds three inspection milestones into SiteBoard's Gantt planning view: a structural frame inspection at day 28 before the second-floor slab is poured, an MEP rough-in certification at day 68 before plastering begins, and the final occupancy inspection at day 115. Each milestone is set as a predecessor to the next phase. On day 25, he logs a preparation task and books the structural engineer. The inspection passes on day 29 — one day late, but the pre-planned two-day buffer absorbs it. The slab pour starts on time. Without the buffer and the dependency link, that single-day slippage would have cascaded into the MEP schedule and pushed the finishing phase by a week.

What happens when an inspection is delayed or fails?

If the inspector cannot attend on the booked date, move the milestone forward in SiteBoard's Gantt planning view and watch downstream tasks shift automatically. You see the knock-on effect immediately rather than discovering it ten days later when a trade crew arrives to find the gate still closed. If an inspection fails — a common result when electrical rough-in is not fully complete before the certifier arrives — add a rework task between the original milestone date and a new re-inspection milestone. Set the re-inspection as the gate for plastering. The schedule then shows the real recovery path, not an optimistic timeline that everyone on site knows is wrong.

How does the owner know when an inspection passes?

When inspections are on the Gantt and the owner holds the sharing link from SiteBoard's owner sharing feature, they see each milestone as part of the live schedule — no separate call needed. A milestone showing as complete with the date it closed tells the owner that the build cleared a legal gate and the next phase is underway. When a milestone slips, the owner sees that too, which means the contractor is managing a problem transparently rather than hiding it. On projects where owners pay in instalments tied to inspection milestones, this visibility removes most friction from payment conversations: the milestone completion date is the documented proof, visible in real time.

What if the authority delays the inspection, not the contractor?

It happens — an inspector is unwell, a public holiday falls on the booked date, or the authority has a backlog. Update the milestone date in the Gantt, note the reason in the task, and let dependent tasks shift accordingly. Do not leave the original date showing while privately knowing it will be missed: that creates two versions of reality and sets up a credibility problem with the owner later. When the delay is clearly outside the contractor's control, the updated Gantt with a task note is the documented evidence that supports a request for a time extension if the contract provides for it. Most owners accept an honest update far better than a surprise.

Can we schedule crane inspections in advance if the date is not confirmed yet?

Yes — add a placeholder milestone at the expected date and label it as an estimate. The three-month inspection cycle means the next date is predictable from the day the crane is installed. Book the engineer as soon as the crane is erected, then lock the milestone date once the engineer confirms availability. Certified lifting equipment inspectors in Thailand are scarce relative to demand, and enforcement tightened after the crane incidents of early 2026, adding further pressure to their calendars. Planning the booking on the Gantt the same week the crane goes up is the safest approach — waiting until the month before often means the only available slot is after the legal deadline.

Does a failed inspection have to be shared with the owner immediately?

There is no legal duty to notify the owner the moment an inspection fails, but transparency is almost always the better business decision. Owners who hear about a failed inspection from a third party — a neighbour, a subcontractor's contact, or an authority notice — trust the contractor less than if they heard it directly. The owner sharing link already shows the milestone as open and incomplete to anyone with the link. A short note added through the on-site progress update feature — for example, MEP rough-in rework required on second-floor bathroom circuit, re-inspection booked for 14 August — is professional and keeps the relationship intact. Most clients understand that inspections sometimes require a second visit; what they struggle to forgive is finding out last.