Late Architect Drawings: Protect Your Schedule

Why do late or revised drawings cause so much damage on site?

Design revisions are responsible for roughly one in five construction schedule slippages, yet the damage is almost never proportional to the size of the change. A single revised window detail can stall the aluminium subcontractor for a week, which delays the waterproofing, which pushes the internal fit-out, which breaks the handover date. Thai SME contractors tend to discover that a drawing has changed when a foreman asks why the printout dimensions do not match what the engineer marked on site — by which point work done to the old detail may need to be redone and the timeline has already moved. The root problem is not the revision itself; it is the absence of a process to absorb and record revisions before they cascade through the programme.

When should you expect drawing revisions and build a buffer into the Gantt?

Any project where MEP coordination, structural details, or finishes are still being resolved at the time of site mobilisation should carry a drawing-revision buffer in the Gantt planning view. A typical residential build of 150 to 300 square metres will see two to four drawing revisions during construction — most arriving around the MEP rough-in stage and again at fit-out when the owner changes a wall layout or the architect adjusts a ceiling height. Insert a floating two-to-four-day review task before any activity that is directly dependent on finalised drawings: MEP rough-in, ceiling layout, tiling patterns, staircase steelwork, and any structural alteration. This buffer costs nothing if no revision arrives and absorbs the impact without breaking the programme if one does.

How do you update the Gantt when a revised drawing arrives mid-build?

There are four things to update the moment a revised drawing lands on site. First, add a task note recording the drawing revision number, date of issue, and the task it affects. Second, adjust the start and finish dates of the affected task to reflect when work can realistically resume. Third, trace all downstream tasks that depend on the revised item and shift their dates forward to match. Fourth, log an on-site progress update noting the reason the task has paused — making clear that the stoppage arose from the revised drawing, not from crew availability or productivity. These four steps take less than ten minutes in SiteBoard but create a dated, visible record of exactly where the delay originated.

How do you communicate a drawing delay to the owner without damaging the relationship?

The moment a revised drawing creates a schedule impact, send the owner the current Gantt through the owner sharing link and point out the specific task that has shifted. A short message — "Revised roof drainage drawing arrived today, MEP rough-in is pushed by five days, you can see the updated dates on the plan" — is far more effective than a phone call where the owner has no visual context. When the owner can see the Gantt move in real time they understand the change came from design, not from slow execution. This transparency prevents the most common source of contractor-owner friction after a delay: the assumption that the site team is at fault for a slippage that originated in the design office.

What does a strong extension-of-time record look like?

An extension-of-time claim for a drawing delay requires three elements: proof that the delay arose from the revised drawing rather than from the contractor's own execution; a record showing when the revised drawing was received versus when the contractor needed it to proceed; and a calculation of the number of working days the revision added to the programme. In SiteBoard, the combination of task notes with drawing revision dates, on-site progress updates citing the reason for stoppage, and the Gantt showing before-and-after dates for each affected task provides exactly this record. Print the Gantt or export the task list alongside the dated progress updates, and the evidence is complete without any additional documentation.

A worked example: a three-storey townhouse in Pathum Thani

During the MEP rough-in phase of a 2.8 million baht three-storey townhouse in Pathum Thani, the engineer issued a revised electrical drawing seventeen days after the original. The revision added a second distribution board on the second floor, requiring the conduit route through the concrete slab to be repositioned. The electrical subcontractor had already started laying conduit to the original route; rework took three days. Because the contractor had logged the original drawing issue date as a task note and recorded the arrival of the revision in an on-site progress update, the delay record was complete. The contractor presented the Gantt showing a three-day slip on the MEP task and a five-day knock-on to the plastering phase. The owner accepted the extension without dispute, and the final handover slipped by only the documented five days.

How do you recover the schedule after a drawing revision?

After absorbing the revision, look three to four weeks ahead in the Gantt and identify tasks that have float — activities not on the critical path whose start can be moved earlier without creating a conflict. Bringing a non-critical finish trade forward by a few days, adding a half-day session to a bottleneck task, or resequencing two independent activities to run in parallel can recover several days of lost programme without overtime across the whole site. The key is to make the recovery decision while you still have schedule slack to work with. A contractor who updates the Gantt the day the revised drawing arrives can make a calm, targeted recovery plan; one who waits until the delay has compounded across three or four tasks is managing a crisis instead.

FAQ: Does receiving a revised drawing automatically entitle the contractor to more time?

Not automatically. An extension of time is warranted when the revised drawing arrived later than the contractor could reasonably have anticipated and prevented work from continuing on the critical path. If the revision affects a task with two weeks of float, there is no critical-path delay even though the drawing changed. If it stops a critical-path task for more than one or two days, the contractor has a documented basis for requesting an extension. The strength of the claim depends entirely on the quality of the record: the dated receipt of the revised drawing, the task note showing when the contractor needed it to proceed, and the Gantt demonstrating the critical-path impact.

FAQ: How far in advance should a contractor request final drawings from the architect?

The practical rule is to request the final approved drawing for any major trade at least three weeks before that trade is scheduled to start on the Gantt. For activities that depend on structural or MEP coordination drawings — piling, slab penetrations, shaft openings — four to six weeks is safer. Log the request date as a task note on the relevant Gantt task and follow up in writing if no drawing has arrived two weeks before the scheduled start. This creates a paper trail that separates a drawing-supply delay from a contractor execution delay if a dispute later arises.

FAQ: What if the owner insists the delay is the contractor's fault, not the architect's?

This argument almost always arises because the owner has no record of when the drawing arrived versus when the work was supposed to start. The contractor's best response is not a counter-argument but a document: share the Gantt showing the original scheduled start, the task note showing the date the revised drawing was received, and the on-site progress update logging when work stopped and why. If those three records are consistent and dated, the contractor's position is straightforward to defend. A disciplined habit of logging drawing revision dates on the Gantt — taking about two minutes per revision — is the cheapest insurance a contractor can carry.