How to Schedule MEP Work on the Gantt Without Losing Weeks

Why do MEP subcontractors cause more schedule slippage than any other trade on a Thai residential build?

MEP stands for mechanical, electrical, and plumbing — on a Thai house build it means three separate subcontractors: the electrical contractor, the plumber, and the air conditioning installer. Each one runs through almost every phase of the project. Electrical conduit must be in before walls close; plumbing stacks must be positioned before the slab is cast; AC drain lines must be run before ceilings go up. Each dependency is hard, each sub operates independently, and each has their own workload. In 2026, specialist MEP capacity in Thailand is tighter than it has been in recent years: electrical and AC subs are carrying more concurrent projects, so their available slots fill earlier. When one MEP trade slips, every trade waiting behind it slips too, and the compounding effect on a 4-to-6-month residential programme can easily turn a two-week delay into a four-week overrun.

What are the four stages of MEP work that every Gantt must include?

MEP work on a Thai residential build runs in four distinct stages. Rough-in is the first: conduit runs, pipe stacks, and AC drain lines installed inside the structural shell before walls are closed. First-fix testing follows, where pressure tests and inspections confirm the rough-in before any plaster or concrete covers it. Second-fix comes after wall finishes are complete: switches, sockets, sanitary ware, and fan coil units are installed. Commissioning is the final stage: everything is powered up, tested, and handed over. Each stage sits at a different point in the programme, involves a different subcontractor, and has a different dependency chain. Mapping all four as distinct task groups in the Gantt planning view turns MEP from a vague block into a concrete programme that the structural and finishing trades can depend on.

How do you set up MEP task dependencies correctly in the Gantt planning view?

Add the MEP rough-in phases as separate bars in the Gantt planning view — one for electrical conduit, one for water supply and drainage, one for AC drain and copper lines. Link each rough-in bar so it starts only after the relevant structural work is complete: electrical rough-in after the RC frame is done, plumbing after the ground-floor slab is cast. Then link the wall-closing task so it cannot begin until all rough-in bars are signed off. This chain means a slipping MEP rough-in automatically pushes the wall close date, the plastering, and every finishing task behind it. You see the full programme impact on the day the MEP task starts running late, not three weeks later when the plasterer is standing on site with nothing to do. Update each task's percent complete daily so the foreman's field report reflects actual MEP progress zone by zone.

A worked example: a 3.2-million-baht townhouse build in Pathum Thani

Khun Wanchai was managing a 3.2-million-baht three-storey townhouse in Pathum Thani on a 24-week programme. He had booked his electrical sub for rough-in starting in week seven, expecting the RC frame on all three floors to be done by week six. The frame finished on schedule, but the electrical sub arrived in week nine — they had committed to a commercial project and could not move their crew earlier. That two-week delay pushed the wall close from week eight to week ten, which pushed plastering to week eleven, painting to week thirteen, and the AC and electrical second-fix to week fifteen. The original plan had those finishing in week thirteen. Two weeks became a four-week overrun because every trade was queuing behind the one that waited on the electrical rough-in. Khun Wanchai now books all three MEP subs in writing before the RC frame begins, with a confirmed date and a fallback contact.

How tight MEP capacity in 2026 changes when you need to book your subcontractors

In previous years, a Thai SME contractor could call an electrical sub two to three weeks before rough-in and expect availability. In 2026, the pattern has shifted. Electrical and AC subcontractors in Bangkok and surrounding provinces are carrying more concurrent jobs, and their open slots fill weeks earlier than before. The practical effect is that you now need to book MEP subs at the same time you book your structural work — when the Gantt planning view first goes up, not when the RC frame is nearly done. The Gantt gives you the exact rough-in start date you need to make that booking call. An MEP sub who receives a firm start date with a project link to confirm it is more likely to hold that slot than one who gets a vague phone call the week before. Sharing the Gantt through the owner sharing link costs nothing extra and makes the commitment concrete on both sides.

Why does tracking MEP progress through on-site updates matter more than tracking structural work?

Structural work is easy to verify: concrete is poured or it is not. MEP rough-in is harder to measure and easy to misreport. A plumbing stack declared done by a sub eager to collect payment and move to the next job may still be missing the top-floor connections. An electrical conduit run that is 80 percent complete goes completely invisible once plaster goes on. Using the on-site progress updates feature in SiteBoard, the site supervisor logs the actual percent complete for each MEP task daily and attaches a photo of the completed zone. This creates a time-stamped record of where the rough-in actually was on any given day — useful for sequencing the wall close and for resolving any payment dispute with the sub later. When the data comes from the site daily, the project manager sees an MEP task stalling two weeks before the wall-close deadline rather than on the morning the plasterer is booked to start.

How to use the owner sharing link when MEP delays affect the handover date

A contractor who tells the owner two more weeks are needed on handover day faces a difficult conversation. A contractor who has been sharing the project through the owner sharing link in SiteBoard faces a different one: the owner can already see that the electrical rough-in task has been at 70 percent for eight days, that the wall close has not started, and that the programme has shifted. The conversation becomes showing what happened and why, not delivering a surprise. When an MEP sub confirms a revised date, update the task note in the Gantt immediately. The owner sees the updated programme without needing a phone call. Transparency about the cause of an MEP delay is not a weakness — it separates a contractor who builds trust from one who delivers surprises at handover.

FAQ: What should you do when electrical rough-in runs late and the plasterer is already booked?

Do not cancel the plasterer immediately. First, check which floors or zones the electrical sub has completed and which are still outstanding. If the ground floor is done and the first floor is partway through, you may be able to start the plasterer on finished zones while the sub finishes the remaining levels. Update the Gantt planning view to reflect zone-by-zone completion and log the actual status in a task note the same day. If the entire floor must be clear before plastering can start anywhere and the sub needs more than three days, notify the plasterer as early as possible. A day's notice costs you nothing; a same-day no-show damages the relationship. Record the revised dates agreed with both subs in SiteBoard so the programme reflects the new reality before the next site visit.

FAQ: How many weeks ahead should you book MEP subcontractors for a 2026 Thai house build?

Book all three MEP trades in writing at least six to eight weeks before the rough-in start date shown on your Gantt. This is earlier than most Thai SME contractors are used to, but it reflects the current market. For a house build where the RC frame starts in week three and MEP rough-in falls in weeks five to seven, your booking confirmation needs to happen by week one — ideally before the project kicks off. When you set up the Gantt planning view at the start of the project, identify the rough-in start date for each MEP trade and add a task note as the booking confirmation deadline. If a confirmed booking does not exist by that date, the Gantt is telling you the programme is at risk before a single MEP crew member has arrived on site.

FAQ: Can the Gantt track all three MEP trades — electrical, plumbing, and AC — on one board?

Yes, and that is exactly how it should be set up. In the Gantt planning view in SiteBoard, create a separate task for each trade at each stage: electrical rough-in, plumbing rough-in, AC rough-in, electrical second-fix, plumbing second-fix, AC second-fix, and commissioning. Group them under a parent task labelled MEP so they collapse into one row when you want a high-level view of the programme. Link each task to its dependencies so that a delay in any one is immediately visible to every task waiting behind it. A fully mapped MEP programme on a single Gantt board eliminates the common pattern where structural and finishing trades are tracked carefully while MEP is managed by phone call and gut feel — the exact condition that turns a two-week MEP slip into a four-week project overrun.