Track Material Deliveries on Your Build Gantt

Why material delays damage your schedule more than slow work

On most Thai SME construction sites, the biggest cause of schedule slippage is not a slow crew or poor technique — it is materials that were not confirmed or tracked far enough in advance. A concrete pour planned for Tuesday stops the moment the rebar does not arrive on Monday afternoon. One missing delivery pushes the pour, which pushes formwork stripping, which pushes the next floor slab, and suddenly three days of missing steel have cost two weeks on the calendar. The problem is rarely the supplier — it is that the delivery was never on the plan. It lived only as a verbal confirmation, and verbal confirmations have a habit of arriving late.

Should material deliveries actually go on the Gantt?

Most contractors treat the Gantt as a schedule for construction work only. But a task like "pour ground-floor columns" has a predecessor that is not another piece of physical work — it is "rebar delivered to site" and "formwork ready." When the delivery is invisible on the plan, the crew discovers it is late only when they arrive on site ready to start and the steel is not there. Adding a delivery task as a formal predecessor on the Gantt turns the problem from invisible to visible: you see the delivery date approaching, you can confirm it a week out, and if it slips you see exactly which downstream tasks are affected before a single crew member shows up to an empty site.

Which materials are worth tracking on the Gantt?

Not every bag of cement needs its own task. Focus on materials with meaningful lead times or that block an entire phase: structural rebar, precast panels, specialty tiles, aluminum or steel window frames, MEP equipment such as electrical panels and water heaters, and any imported or custom-made items. Same-day or next-day materials — standard brick, sand, general cement — do not need Gantt tasks because you can order them on short notice without risk. A practical rule covers most projects: if a late delivery would stop the crew for more than one working day, put it on the plan with a due date and a linked successor task.

A worked example: apartment fit-out in Bang Na

Consider Khun Apinya running a 1.8-million-baht apartment fit-out in Bang Na, a ten-week job. Her plan includes window installation in week eight, electrical fit-out in week nine, and final floor tiling in week ten. She adds three delivery tasks to her Gantt: aluminum window frames due by week seven, the electrical panel due by the start of week eight, and imported Italian floor tiles — which carry a six-week supply lead time — due by the end of week seven. When she reviews the plan in week three, she realises the tiles must be ordered now, not when plastering begins in week five. She places the order that afternoon. The tiles arrive in week seven as planned. Without the delivery tasks in the Gantt, she would have thought of ordering in week five and received the tiles in week eleven — a week after the tilers were scheduled to finish.

How to set up a delivery task on the Gantt

A delivery task is a standard task with three specific settings. First, name it clearly: "Rebar delivery — ground floor columns" is better than just "Rebar" because it tells anyone reading the plan exactly which work it feeds. Second, set the due date to the day you need the material on site, not the day you plan to order it — the order date goes in the task's description or notes. Third, link the downstream construction task as a successor so that if the delivery slips, the work task shows as delayed automatically. That chain — delivery task to work task — is what gives the Gantt the ability to surface a supply problem before it becomes a site problem.

What to do when the supplier says delivery will be late

When a delivery task slips, the Gantt immediately shows which work tasks are now at risk. The first question is whether the affected task sits on the critical path or whether it has float. If there is float, a two-day slip absorbs quietly without touching the handover date. If the task is critical, you have a clear set of options: chase an alternative supplier, split the order and pull forward what is available, or find non-critical work the crew can advance while waiting. The Gantt makes this decision fast because you see the cascade before you pick up the phone. Most supply problems that turn into crises are ones where the contractor saw the slip too late to do anything but absorb the full impact.

Log delivery arrivals as progress updates

When a material arrives on site, mark the delivery task complete in the project plan — not just in memory. Add a photo of the delivery: the loaded truck, the stack of rebar on the ground, the equipment uncrated. Add a short note with the quantity received and the date. SiteBoard's on-site progress updates work the same way for a delivery task as for any construction task: tap the task, mark it at one hundred percent, snap a photo, done. This record matters when a dispute arises later about whether a delay was caused by a late material or slow work. A timestamped update with a delivery photo inside the Gantt is the difference between a clear account and a version of events nobody can verify.

How far in advance should you order materials for a Thai build?

Standard local materials — cement, sand, standard brick — can usually be ordered three to five days out without risk. Rebar and structural steel in standard sizes need one to two weeks. Locally made aluminum and steel window frames need two to three weeks; imported ones need four to six weeks. Specialty tiles, imported MEP equipment, and custom or prefabricated elements can carry lead times of six to twelve weeks — longer if there are port clearance delays at Laem Chabang. Build the order trigger into the Gantt as a note on the delivery task: "Order by week four to ensure week seven delivery." That note turns the delivery task into a procurement reminder the plan enforces, not one that depends on memory.

Can the Gantt track material sample approvals as well as deliveries?

Yes, and for projects where an owner or engineer must approve material samples before fabrication or import, adding an approval task between the specification step and the delivery task is worth doing. A three-step chain — submit samples, receive owner approval, deliver material — captures the full procurement sequence inside the plan. If the owner takes two weeks to respond instead of one, the delivery date slips visibly on the Gantt and you can respond immediately. Without that approval task in the plan, the review step is invisible and the delay feels random when it finally shows up at the delivery stage.

Does adding delivery tasks make the Gantt harder to read?

In the short term the plan has more rows, but in practice it becomes more honest rather than more complicated — you are showing work that is genuinely happening alongside the physical construction it supports. Projects that track deliveries on the Gantt typically have fewer surprises in the first half of the build, when materials are arriving and construction is accelerating. The added tasks pay for themselves the first time a delivery task alerts you to a coming gap early enough to reorder before any crew member loses a waiting day. One idle crew day on a typical Thai SME site costs more than the ten minutes it takes to add three delivery tasks at the planning stage.

What if the material arrives damaged or wrong specification?

Log the delivery task as a partial update — say fifty percent complete — with a photo showing the defect or the wrong specification, and a short note describing the problem. This keeps the delivery task in-progress, which in turn keeps the downstream construction task blocked on the plan. When the replacement arrives, close the delivery task at one hundred percent with a new photo and note. The result is a complete, timestamped record: material arrived on this date in the wrong condition, documented with photo; replacement arrived on this date; construction started on this date. That sequence is what you show the owner when they ask why the pour ran three days late — not slow work, but a documented supply issue with the evidence to back it.