They Signed Off on the Opening, Then Came Back Wanting It Bigger

 An SWC signed off on an opening position last month. Size confirmed, pipe sleeve dimensions confirmed, their name on the M&E drawing. Three weeks later they came back and said the actual equipment doesn't fit, they need it bigger, and by the way there's another spot where they need one too.

I've stopped being surprised by this. I haven't stopped being irritated by it.

We alternate two meeting cycles with the services-wide contractors. Week one is SWC coordination. Week two is CCSM, the coordinated combined services model, where each contractor builds their own model with real installation details, cable routing, support spacing, headroom clearances. Then back to SWC, then CCSM. Fortnightly each, forever. I can tell what kind of week I'm in by which one's on the calendar.

There's a specific kind of tired that comes from these meetings. Not physically demanding, just two hours of holding four contractors' requirements in your head at once while somebody argues about a bracket. I usually need about twenty minutes at my desk afterward before I'm any use for anything else.

What Happens When Someone Wants a Hole

The request is always simple. Position, size, done. That part takes them thirty seconds to send.

Then I pull the latest approved structural drawings, the current site shop drawings, and make sure the model matches both, pushing every revision to the cloud so nobody's working off something stale. Then I combine every SWC's individual model into one, because a request that looks completely fine on its own stops looking fine the moment four other contractors' services are sitting on top of it.

Then the structural side. Rebar spacing at that exact spot. Bar positions. Minimum concrete cover. Whether there's actually room for a human being to install anything there. Whether it fouls another SWC's routing that's already been agreed and signed.

Only after all that does it go into shop drawings, then as-built, then someone actually cuts concrete.

Nobody notices any of this when it works.

combined services model displayed on meeting room screen during coordination review

The Jet Fan Nobody Could Fix

This one started years before I could have touched it. At tender, the jet fan section was documented as not needing a recess in the roof slab. So the roof slab got built that way. Poured. Cured. Finished.

Then the jet fan contractor came on board and modelled their equipment at actual size. Over the 0.8m service envelope, into the 5.1m clear headroom.

I remember checking that overlay twice before saying anything, because if I was going to tell a room full of people that a completed slab was a problem, I wanted to be certain it wasn't me misreading a level. It wasn't.

There's no fixing concrete that's already there. In the end the jet fan contractor reworked their own specification, adjusting the fan and silencer until the assembly stayed clear. It resolved fine. It still sat badly with me for weeks, mostly because nobody had done anything wrong, everyone had just trusted a document that turned out to be optimistic.

The Presentation I Actually Cared About

The messier one was in the same area. A 900mm existing water pipe sat exactly where the roof slab needed to go, and its diversion was scheduled after the pour. That alone is a problem. This stretch also needed the jet fan recess, and it tied into an at-grade road diversion, so it wasn't contained to our scope at all.

We went through it internally, then with the designer, and built out several alternatives rather than walking in with one option and hoping nobody pushed. I didn't want to be the guy asserting something was necessary without being able to show the cost of not doing it.

Then I presented it to the client. Why the recess had to extend, what the programme delay looked like without it, what the money looked like either way, each option laid out with the numbers behind it. I spent most of two evenings putting that deck together after the kids were asleep, redoing the cost comparison table twice because the first version buried the point.

It got approved. I don't get many days like that. I told my wife about it over dinner, which I almost never do with work things, mostly because most of what I do doesn't compress into a sentence anyone outside this industry would find interesting.

tunnel roof slab construction with reinforcement in place

The Hacking We Already Know About

Not everything gets caught in time, and I'd rather say that plainly than pretend the model saves everything.

There's a spot where the main tunnel roof slab and the slip road base slab intersect. There's a slab thickening of about 1.8m at that junction for the temporary king posts. Because of how the slip road rises across the main tunnel, that thickening clashes with the slip road wall up into the roof slab, and it hits the slip road's cable brackets and service envelope too.

No clever fix exists. It gets hacked. The stretch is longer than anyone wants it to be.

What we could do was make sure nobody discovers it mid-construction. Design team knows, construction team knows, designer knows. Everyone can plan around it now instead of finding out the week it blocks them.

Sign-Off Means Less Than You'd Hope

Back to where I started. If shop drawings haven't progressed yet when they come back wanting changes, fine. We absorb it, update, move on. That happens constantly and honestly isn't worth the energy of a fight.

After shop drawings are issued and approved, it's different. Then the first answer is no, we can't provide that. Sometimes that's where it stays. Sometimes it becomes clear there's genuinely no other option on their side, and we go back to the design team and find a way anyway.

Sitting in the middle of that is most of what this job actually is. Knowing when no protects the programme and when no is just delaying something inevitable while everyone burns a fortnight.

When the Answer Is Rebar

Sometimes no is real and structural. Large openings need heavy, tight reinforcement around them, and there are positions where a hole genuinely cannot go without compromising something.

Every opening gets reviewed with the structural engineers off the combined model. When it comes back as no, I don't just forward the rejection. I go back with somewhere else it could sit. Shift it a bit. Try the adjacent bay. Split it into two smaller penetrations.

They accept almost every time, as long as the size holds and the new position isn't far off. Nobody argues with a structural constraint. What people push back on is a no with nothing attached to it, and honestly, fair enough.

That's the week, most weeks. Meetings, overlays, structural checks, and a long-running argument about holes in concrete that nobody walking through the finished tunnel will ever know happened.

Related reading:

Why Cutting a Hole in a Concrete Wall in Revit Is Never as Simple as It Sounds

The Duplicate Family That Cost Us Two Weeks on a Tunnel Ventilation Shaft

Getting Through LTA's BIM Submission Process Without Losing Your Mind

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