The question only comes up after the rebar is already tied
By the time someone asks 'whose sheet shows this penetration?', the framing plan is stamped, the deck is being laid, and the MEP coordination drawings are still catching up. That gap is where the money leaks: a 6-inch storm leader that nobody dimensioned ends up as a field core through a post-tensioned slab, a frantic RFI to the SER, and a half-day stop-work while everyone figures out whether the tendon got nicked. The honest root cause is rarely a single person 'forgetting' — it's that locating, sizing, reviewing, and physically placing a penetration are four different jobs owned by four different parties, and nobody confirmed the handoff before concrete was scheduled. Settle the split early and the penetration becomes a cast-in sleeve on a coordinated sheet instead of a destructive-test problem on the punch list.
The default responsibility split (and why it lands where it does)
There is a clean logic to who owns what, and it follows the information, not the org chart. The trade that *needs* the hole defines it; the engineer who owns the *structure* polices it; the contractor who owns the *means and methods* places it.
- MEP engineers (mechanical, electrical, plumbing, fire protection) LOCATE and SIZE every penetration their systems require — duct mains, plumbing risers, conduit banks, sprinkler drops, cable trays. They originate the geometry: x/y location, elevation, diameter or W x H, and the system it serves. They are the authors of the demand.
- Structural engineer of record (SER) REVIEWS and APPROVES. The SER sets the rules — maximum opening size, keep-out zones near columns, beam ends, and supports, spacing relative to web depth on steel beams, and any added reinforcement (trim bars around slab openings, web stiffeners, reinforced sleeves). Penetrations outside the allowable envelope get redesigned or relocated, not waved through.
- Architect / GC COORDINATES. The architect resolves penetrations against the design intent (fire/smoke ratings, acoustic separations, finished ceilings) and the GC drives the BIM/clash-coordination process that forces MEP geometry and structural limits into the same model before fabrication.
- Contractor / concrete sub PLACES the sleeves — sets cast-in sleeves, box-outs, and inserts per the coordinated drawings before the pour, and is the party held to 'no field coring without engineer approval.'
Where the structural engineer actually draws the line
The reason penetrations route through the SER is that a hole in a structural member is a hole in the load path. The general relationships practitioners design around — verify the exact numbers against your project's structural notes and the governing code, never against a rule of thumb: openings are kept away from regions of high shear and high moment (near supports and at beam ends on a steel framing member; near columns and over column strips in a flat-plate slab); larger openings demand added reinforcement or local thickening; clustered penetrations are treated more conservatively than isolated ones because the net section governs. On post-tensioned slabs the stakes jump — tendon locations must be known before any sleeve or core, which is exactly why PT decks carry the hardest 'no unapproved coring' rules. The takeaway for coordination: MEP cannot finalize a penetration as 'approved' on the strength of fitting through the model. It is approved when the SER has reviewed it against these limits and detailed the reinforcement. Model clearance is necessary; it is not sufficient.
The one event that has to happen before the pour: sign-off
Everything above collapses into a single non-negotiable gate — the SER (and architect for rated/acoustic conditions) signs off on the coordinated penetration set before concrete is placed or steel is fabricated. Cast-in sleeves are cheap and clean; field core-drilling is expensive, destructive, schedule-killing, and on a PT or heavily reinforced member, genuinely risky. The sign-off converts a downstream RFI-and-repair loop into an upstream review. Make the gate explicit in the coordination schedule: penetration drawings issued, structural review returned, reinforcement detailed, sleeves located on the placing drawings — then pour. If a penetration shows up after that gate, the default answer is a formal RFI to the SER, not a drill bit.
- Pre-pour checklist: MEP penetration drawings issued with location, size, and system
- Structural review returned — within allowable size and keep-out zones, or flagged for relocation
- Added reinforcement / sleeve details provided by SER where required
- Penetrations cross-checked against the coordinated BIM model (no unresolved clashes)
- Sleeves and box-outs located on the contractor's placing/shop drawings
- Architect confirms fire, smoke, and acoustic ratings at each penetration
- Written sign-off captured before the pour is scheduled — no field coring without SER approval
How this maps to your deliverables across SD, DD, and CD
Penetration coordination is not a single drawing — it threads through the phases. In SD it barely exists beyond gross shaft and chase locations. In DD, MEP system routing firms up and the structural framing concept sets the constraints; this is when major risers and shafts get reserved. By CD, the coordinated condition has to be documented and stamped: MEP plans show the penetrations, structural framing plans and details show the openings with their reinforcement and sleeve callouts, and architectural sheets carry the rated-assembly details. The clash-coordination / BIM model is the working surface where MEP geometry and structural limits collide before any of those sheets are finalized. Output: a set of MEP penetration plans, structural framing sheets with opening details, and sleeve placing drawings that all agree — which is the entire point of getting the responsibility split right before the model is locked.
| Task | MEP Engineer | Structural Engineer (SER) | Architect / GC | Contractor |
|---|---|---|---|---|
| Locate & size the penetration | Responsible | Consulted | Consulted | Informed |
| Review against structural limits (size, keep-out, reinforcement) | Consulted | Responsible / Accountable | Informed | Informed |
| Detail added rebar / reinforced sleeve | Informed | Responsible | Informed | Informed |
| Coordinate clashes in BIM model | Responsible | Consulted | Accountable (GC) | Responsible |
| Confirm fire / smoke / acoustic rating at penetration | Consulted | Informed | Responsible (Architect) | Informed |
| Sign off before the pour | Consulted | Accountable | Consulted | Informed |
| Place cast-in sleeves / box-outs | Informed | Informed | Consulted | Responsible |
| Approve any field core-drilling | Consulted | Accountable | Informed | Requests |
Frequently asked
Does the architect ever draw the penetrations themselves?
Generally no. The architect coordinates penetrations against design intent — fire/smoke ratings, acoustic separations, ceiling heights — and may show large architectural openings (shafts, chases) on their plans. But the dimensioned MEP penetrations that pass through structure originate on the MEP engineer's drawings and are governed by the structural engineer. The architect's role is integration and rated-assembly detailing, not authoring the penetration geometry.
Who is liable if a sleeve is missed and the slab has to be core-drilled?
It depends on where the breakdown occurred, and that's exactly why the pre-pour sign-off matters as a paper trail. If MEP never showed the penetration, the demand was never authored. If it was shown but not reviewed, the coordination gate failed. If it was reviewed and approved but the contractor didn't set the sleeve, placement failed. A clear RACI plus a documented sign-off before the pour is what lets a team assign responsibility instead of arguing — and more importantly, prevents the miss in the first place.
Can MEP just core-drill in the field instead of coordinating cast-in sleeves?
Not without structural approval, and never assume it on a post-tensioned or heavily reinforced member. Field coring risks cutting rebar or tensioned tendons, which can compromise the member. Cast-in sleeves coordinated before the pour are faster, cheaper, and safe. The standard rule is no field core-drilling without the structural engineer of record's written approval, often requiring GPR/X-ray scanning to locate reinforcement first.
What's a 'keep-out zone' for penetrations?
It's the region of a structural member where openings are restricted or prohibited because the member carries high shear or moment there — near supports and beam ends, adjacent to columns, and over column strips in flat-plate slabs. The structural engineer defines the allowable envelope; penetrations that land in a keep-out zone get relocated or require specific added reinforcement. Always verify the exact zones and dimensions against your project's structural notes, not a generic rule of thumb.
At what project phase should penetration coordination be locked?
Major shafts and risers should be reserved in DD as MEP routing and the structural framing concept mature. The coordinated, reviewed, and signed-off penetration set has to be complete by the end of CD — and critically, before the specific pour it affects is scheduled. The BIM clash-coordination process is the working surface where it gets resolved before any of those sheets are stamped.