Beam Soffit, Door Height and a Pipe Nobody Drew
A two-storey government higher secondary school block is under construction from a drawing set issued for construction at 1:100. The architectural floor plan shows the corridor wall as 230 mm brickwork; the structural drawing for the same wall shows a 230 mm × 450 mm plinth beam. In the architectural section, finished floor level is +0.450 m and the underside of that beam is at +2.550 m. Door D2 on the corridor is scheduled as 2100 mm × 1000 mm and sits directly below the beam; floor finish is 40 mm thick Kota stone. Separately, the plumbing layout shows a 110 mm diameter rainwater downpipe crossing that plinth beam 300 mm from the column face, but the beam reinforcement drawing shows three 16 mm bars running continuous through that zone, with no sleeve or opening marked. Masonry in that wall has already been raised to 1.2 m. The contractor's site engineer says 'we will manage at site' and proposes reducing the door height by 50 mm.
1. Identify each conflict, show the arithmetic that proves it, and state which can be settled by the site engineer and which cannot.
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Conflict 1 - door D2 against the plinth beam. Clear height from finished floor to beam soffit = 2.550 − 0.450 = 2.100 m. Deduct the 40 mm floor finish: available = 2.060 m. The door leaf and frame must sit on the finished floor and need 2.100 m clear. Shortfall = 40 mm. The door cannot be fitted as drawn, and the beam soffit cannot be lowered locally without changing the structural depth.
Conflict 2 - 110 mm downpipe through the beam. A 110 mm hole is 25% of the 450 mm depth and sits in the high-shear zone 300 mm from the column face, where the three 16 mm bars run. A hole of that size there, without a designed sleeve and without cutting the bars or adding trimmer bars, needs a structural check on shear capacity and bar curtailment. It is not a 'drill it and see' item.
Conflict 3 - masonry already at 1.2 m. This is not itself a clash (masonry is below the beam), but it tells you the mason is working from a drawing he believes is correct, so the resolution must reach him as a controlled revision before he reaches the beam.
Who decides: reducing the door height to 2050 mm is an architectural change that affects the schedule, the frame order and the door supplier's contract - outside the site engineer's authority. Raising the beam or altering the FFL would change structure and drainage levels. Drilling the beam is a structural decision. All three must go to the architect and structural engineer for written direction; the site engineer may only stop work and record the query. The 'manage at site' route produces a non-compliant building and an unapproved deviation for which the contractor bears the cost.
2. Draft the query (RFI) you would raise and describe how the revised drawing is controlled so the same error does not reach the mason twice.
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RFI content - make it answerable without a site visit:
- Drawing numbers, titles and revision marks of both conflicting sheets (architectural A-04 Rev 0, structural S-07 Rev 0, plumbing P-02 Rev 0).
- Grid reference and clear location description ('corridor wall, grid C–D, door D2').
- The dimension chain and the arithmetic: FFL +0.450, beam soffit +2.550, finish 40 mm, door 2100 mm, resulting shortfall 40 mm.
- A small marked-up sketch plus a photograph showing masonry height.
- Options with consequences: (a) raise beam soffit to +2.650 m - effects on storey height, staircase, beam depth; (b) reduce finish to 20 mm - effects on level matching corridor; (c) reduce D2 to 2050 mm - effects on door schedule, frame already ordered; (d) shift the pipe to a sleeve outside the shear zone.
- Programme and cost impact, and the date by which a reply is needed (before masonry reaches the beam).
- Signature of the contractor's engineer, entry in the RFI register, numbered, with date.
Revision control: the response is issued as a formal revision (Rev 1) with the changed area clouded and a revision triangle on the sheet. The superseded Rev 0 prints are withdrawn from the site, stamped 'SUPERSEDED' and filed; only the drawing register holder issues copies. The mason receives a marked-up setting-out sketch signed by the site engineer, and the change is entered in the site instruction book, in the drawing register and, if it affects quantities, in the variation register. Before the beam is cast, the revised position is re-checked by tape and recorded - the same check that should have caught this before masonry started.