Owner-Supplied Materials: Schedule What You Don't Control

What is owner-supplied material and why does it create scheduling risk?

Owner-supplied material — any item the client purchases directly and delivers to site for your crew to install — is common in Thai SME construction. Owners buy their own floor tiles to save on margin, specify a light fitting they found at a trade fair, or insist on a kitchen brand the contractor does not stock. The arrangement can work well when delivery lands on time with the right specification. The problem is that most owners treat purchasing as a separate activity from the build schedule. They order when it feels right and assume the material will arrive around the time the trade needs it. When it does not, your electrician, tiler, or joinery team arrives at a prepared surface with nothing to install — and the cost of that idle day falls on the project.

How do you add owner-supply tasks to the Gantt planning view?

Treat owner-supplied delivery as a task just like any trade, with a start date, a due date, and a dependency linking it to the work that needs the material. In the Gantt planning view, create a task called "Owner: confirm tile delivery" or "Owner: fixture delivery to site" and set its due date at least one week before the installation trade begins. Mark that task as the dependency for the tiling or MEP task that follows. Now the link is visible: if the delivery task slips, the installation task moves automatically and everyone can see the ripple before it happens. Without that task on the plan, the delivery exists only in a phone call or a LINE message — and when the trade arrives with no material, there is no record of when delivery was expected or who was responsible.

A worked example: a Nonthaburi house build with owner-supplied tiles and fixtures

Khun Wiparat was managing a 2.2-million-baht single-storey house build in Nonthaburi. The owner wanted to supply bathroom tiles, kitchen splashback, and all light fittings — roughly 180,000 baht of material. Wiparat added three owner-supply tasks to the Gantt: tile delivery due in week 8 (one week before tiling began), splashback delivery due in week 10, and fixtures delivery due in week 13 before electrical fit-off. The owner could see all three tasks on the owner sharing link. By week 7, the tile delivery task was still at zero percent and the owner had not yet placed the order. Wiparat's project manager flagged the open task in the weekly check and called the owner. The order went in three days later; tiles arrived on day 54 — two days before tiling began — and the trade ran on schedule. Without the Gantt task making the gap visible, the problem would have surfaced the morning the tiler arrived with no material.

What happens when owner-supplied material arrives late?

Late owner-supplied material creates a cascade that is often worse than a trade running late, because the contractor has less control over the fix. If your subcontractor is delayed, you can negotiate, accelerate, or resequence. If the owner's tiles are sitting in a warehouse because the owner has not cleared the delivery invoice, you can call and explain, but you cannot move the material yourself. The cascade is predictable: tiling cannot start, plastering cannot be signed off, the joinery team arrives a week later in a room that is not ready. Each idle day costs money — labour standing by, subcontractors moving to other sites and losing their slot in your project. In a 12-week project, a one-week delay in owner-supplied tiles often becomes 10 to 14 days lost at handover once the rescheduling compounds.

How far in advance should you lock in the owner's delivery dates?

Lead times vary significantly by material type. Standard tiles from a local showroom typically need two to three weeks from order to site delivery. Custom or imported tiles, joinery, and fitted furniture need six to ten weeks. MEP fixtures from overseas suppliers can run eight to twelve weeks. The rule of thumb is to confirm the order is placed at least four weeks before the installation trade begins for anything not off the shelf. For long-lead items, confirm immediately after design is finalised — not after the slab is poured. Build a shared checklist of every owner-supplied item with expected order date and delivery date, attach it to the relevant task in the Gantt, and review it at the weekly site meeting. This turns a personal responsibility into a tracked project deliverable.

Documenting material condition on arrival to protect against rework claims

Owner-supplied material that arrives damaged or to the wrong specification creates a second risk: who absorbs the rework cost. When your team installs tiles the owner supplied and cracks appear six months later, both parties claim the other is at fault — the owner says installation was poor, the contractor says the tiles were substandard. The fix is to document delivery before a single piece is installed. The foreman checks the spec against what was ordered — tile grade, dimensions, colour code — counts the quantity, notes any visible damage, and captures everything in an on-site progress update with photos. That record is timestamped and attached to the delivery task in SiteBoard. If the spec is wrong, installation does not begin: the owner is notified immediately with photo evidence and a clear note that work is paused until the correct material arrives.

Using the owner sharing link to make delivery responsibility visible

The most common failure mode with owner-supplied material is informal chasing through LINE messages that feels like nagging. Sharing the live Gantt through the owner sharing link changes the dynamic. The owner sees the delivery tasks in the same view as the construction tasks — they see that their tile delivery is due in ten days and the tiling trade begins in three weeks. When the delivery task is still at zero percent in week seven, the owner notices without the contractor having to send a reminder. That self-visibility shifts the conversation from contractor chasing to owner managing their own deliverable. It also creates a written record: the date the task was visible, the date it moved, and who acted — without a single additional email or call.

What if owner-supplied material arrives after the trade has already moved to another project?

When a trade team moves to another site because owner materials were delayed, getting them back is not instant. Electricians and tilers work across multiple projects and cannot always drop commitments on short notice. A delay of more than one week typically means rescheduling the trade — sometimes two to three weeks later than the original slot. The cost of that wait is real: the project stalls and running costs continue. When material finally arrives, update the relevant task in the Gantt immediately, notify the trade of the new start date in writing, and use the new confirmed date as the basis for any schedule recovery conversation with the owner. A revised Gantt showing the impact of the late delivery is far more persuasive than a verbal explanation of why the project is behind.

FAQ: Can the contractor be held responsible for delays caused by owner-supplied material?

No — provided the delay is properly documented and the contractor gave reasonable advance notice of the required delivery date. A contractor who placed the delivery date in the Gantt, flagged it in writing when it was approaching without confirmation, and documented the actual late arrival has a clear record that the delay originated outside their scope. Thai construction contracts typically allow a contractor to claim an extension of time for owner-caused delays, but only when the delay is documented — not when it is a verbal understanding. Keep every communication about owner-supplied material in writing: a LINE message screenshot is acceptable, a phone call with no follow-up is not. The Gantt task record, the delivery photo, and the written flag combine to make the contractor's position clear if a dispute arises later.

FAQ: How do you handle owner-supplied material that arrives with the wrong specification?

Stop. Do not install. Send a written notification — LINE or email — to the owner the same day delivery arrives, with a photo showing the discrepancy between the ordered specification and the delivered item. Record in the on-site progress update that installation is paused pending the owner's decision. The owner then has three paths: exchange the material for the correct item, instruct the contractor in writing to proceed with an agreed substitution, or accept a delay to the installation trade while the exchange is arranged. Under no circumstances should the contractor install owner-supplied material that does not match the agreed design without written owner authorisation — the contractor will still be held responsible for the final result even when the material was owner-supplied. Once the correct material arrives and is confirmed, reopen the installation task in the Gantt planning view and resume from there.