How to Use Your Gantt to Control Rising Material Costs

Why are rising material prices in 2026 hitting Thai SME contractors harder than larger firms?

For a large construction company, a 6 percent rise in steel prices is an uncomfortable cost variance. For a Thai SME contractor running a 2-to-4 million baht residential or renovation project, the same increase can wipe out the margin entirely. Materials make up roughly 45 percent of a typical Thai contractor's cost structure — higher than labour, higher than equipment, and far higher than any other single category. In 2026, steel and iron products rose more than 6 percent year-on-year, cement-related materials increased by more than 5 percent, and asphalt-based products climbed above 15 percent. When you quote a project at a fixed price, every week that passes between the quote date and the purchase date is a week of price risk you carry entirely on your own.

How does the Gantt planning view become your material procurement calendar?

Most contractors think of the Gantt as a work schedule — a chart that shows when tasks start and finish on site. It is also a procurement schedule if you read it backward. For any task that requires a significant material order, count back from the task start date by the lead time for that material. The date you land on is the latest safe purchase date. The Gantt planning view in SiteBoard shows every task with its start date on the timeline, so you can scan the full project at once and identify all your purchase windows in a single sitting. If structural steelwork is scheduled to start in week five, and structural steel takes four weeks to source and deliver, your order must go out in week one — not when the task is about to start and not after price notifications land in your inbox.

What are the standard material lead times to plan for on a Thai residential build?

Lead times vary by material and supplier, but these ranges give you a working baseline for a typical Thai house or renovation build. Ready-mix concrete is ordered three to five days in advance, coordinated with the pour date. Structural steel and rebar typically need three to four weeks from order to delivery on standard sizes; special sections or large volumes may take longer. Wall and floor tiles need two to four weeks if ordered from stock, and four to eight weeks for a less common size or finish. Aluminium windows and doors from a fabricator generally need four to six weeks. Roofing sheets and waterproofing rolls are usually available within one to two weeks. Confirm these windows with your regular suppliers at the start of each project, because lead times lengthen during high-activity periods.

A worked example: a 2.6-million-baht house build in Nonthaburi

Khun Somchai won a contract to build a two-storey house in Nonthaburi for 2.6 million baht, with structural work starting in week five of the programme. When he laid the project out in the Gantt planning view of SiteBoard at the start of the build, he counted back four weeks from week five and marked week one as the latest date to lock in his rebar and structural steel order. He called his regular steel supplier that same week and confirmed prices in writing. Between the order date and delivery, the steel price index moved up about 4 percent — a figure that would have added approximately 40,000 baht to his materials bill if he had waited and ordered at the market rate closer to the pour date. Khun Somchai was not lucky; he read the Gantt, calculated the lead time, and made a deliberate purchasing decision while the project was still early enough to act.

Should you stockpile materials early or buy just-in-time when prices are rising?

Both strategies have a cost, and the Gantt helps you decide which applies to each material category. Buying early protects against price increases but ties up working capital — money that could be active on the next project instead. Buying just-in-time keeps cash free but leaves you exposed to the price on the day you order. For high-value, long-lead materials with clear upward price movement — structural steel in a rising market, for example — buying two to three weeks ahead of the Gantt task date is a reasonable hedge. For fast-moving commodity items such as ready-mix concrete or paint, ordering close to the task date is standard practice. Use the Gantt to identify your high-exposure purchase decisions early in the project, then make each one deliberately rather than by default when the task start date arrives.

How does sharing the project view with the owner protect you in cost renegotiations?

Fixed-price contracts give the owner certainty, but they put all material price risk on the contractor. When costs rise significantly between quote and construction, a contractor who cannot show a clear schedule and purchase record is in a weak position in any renegotiation. Sharing the project through the owner sharing link in SiteBoard gives the owner a transparent view of when materials were needed, when they were ordered, and what the programme looked like at the time each commitment was made. If a cost variation has to be discussed, you bring the owner a factual, dated record rather than a verbal explanation and a new invoice. A read-only shared view that shows the programme alongside task notes creates a professional basis for a cost conversation, because the owner can see the scheduling context rather than just the changed number.

FAQ: What should you do when a supplier's price quote expires before your scheduled purchase date?

Update the relevant task in SiteBoard to reflect the revised purchase window, and contact the supplier before the quote expires to negotiate an extension or a partial advance commitment. In a rising market, many suppliers will hold a price for two to four weeks if you give them a firm purchase date and a rough volume estimate. If the quote cannot be extended and the new price is significantly higher, update your project cost estimate immediately and open a conversation with the owner before the purchase is made — not after. Documenting the original quote, the expiry date, and the new price in a task note at the time it happens gives you a clear record if the cost difference becomes a variation claim or a contract discussion later.

FAQ: How do you decide which materials to lock in now versus which to wait on?

Use two criteria: lead time and price volatility. Materials with a lead time of three weeks or more and visible upward price movement deserve an early decision — structural steel, aluminium fabrications, and special-order tiles fall into this category. Materials with short lead times and stable prices can be ordered close to the task start date without meaningful risk. Look at your Gantt and flag every task in the first quarter of the programme that depends on a long-lead material. For each flagged task, check whether prices are rising, flat, or uncertain. If rising, decide whether to commit early. If flat, order at standard lead time. If uncertain, get a written quote with the longest validity the supplier will offer, then re-confirm one week before the order must go out.

FAQ: Does this procurement approach work when managing several projects at once?

Yes — and it becomes more valuable, not less. When you are managing two or three projects simultaneously in SiteBoard, you can see the material demand across all of them at the same time and combine orders for the same material type across projects to negotiate a better price per unit with a shared supplier. A foreman updating task progress through on-site progress updates on one project immediately shows whether that project is running ahead of or behind the purchase dates you planned, so you can adjust an order on a second project if your capacity or the supplier's delivery schedule allows it. Volume consolidation is one of the real advantages an SME contractor gains from having all projects on one board — it turns individual purchase decisions into a supply conversation with more negotiating leverage.