Preconstruction Team — Multifamily Residential
Representative scenario based on typical Helonic usage patterns
620 in a 280-unit project
$210K in estimated savings
Unit coordination & fire sep.
The Challenge
A developer's preconstruction team was reviewing construction documents for a 280-unit, five-story multifamily residential project. Multifamily construction is uniquely challenging for drawing review because design errors in a single typical unit can multiply across 280 units — a misaligned plumbing stack in one unit type means dozens of field conflicts when that unit repeats across every floor.
The drawings showed eight unit types with mirrored and stacked configurations. The preconstruction team suspected coordination issues in the plumbing riser diagrams — the waste stack locations on the plumbing plans didn't appear to align with the structural slab penetrations shown on the structural plans for several unit types. Additionally, the fire separation assemblies between units referenced different UL assembly numbers on different floors of the same building.
The team had three weeks to complete their review before the GMP deadline, and their estimator needed a reliable count of coordination issues to build appropriate contingency into the budget.
How They Used Helonic
The preconstruction team uploaded the full drawing set to Helonic and focused the review on the three areas that drive the most multifamily rework: unit-to-unit coordination (ensuring repeating units are consistent across floors), plumbing stack alignment (verifying that waste stacks, vent stacks, and water risers align through all floors), and fire separation verification (confirming that fire-rated assemblies between units and at corridor walls are consistent and code-compliant).
Helonic's analysis identified 620 issues across the project. The plumbing stack alignment findings confirmed the preconstruction team's suspicions: 47 locations where waste stack centerlines on the plumbing plans didn't match the slab penetration locations on the structural plans. When multiplied across the repeating unit types and five floors, this represented 188 individual field conflicts that would have required core drilling or slab modification.
The fire separation analysis revealed 34 inconsistencies in UL assembly references — three different assembly numbers were used for what appeared to be the same demising wall condition on different floors. Helonic also flagged 89 unit-to-unit coordination issues where mirrored unit layouts created conflicts at shared plumbing walls.
Results
The preconstruction team used Helonic's findings to build a detailed risk register for the GMP proposal. The 47 plumbing stack misalignments alone represented an estimated $210,000 in potential rework if discovered during construction — the cost of core drilling five floors of concrete slabs, rerouting waste lines, and re-inspecting fire-stopping at each penetration.
By identifying these issues before the GMP was locked, the team was able to require the design team to resolve the stack alignment and fire separation issues as a condition of the GMP agreement. This transferred the coordination risk back to the design team — where it belongs — rather than carrying it as contractor contingency.
The team also used the repeating-unit analysis to establish a quality benchmark: once the typical unit coordination was resolved in the drawings, they could be confident that the fix would propagate correctly across all 280 units. This reduced the post-correction review scope from 280 units to just the eight unique unit types.
“In multifamily, one plumbing stack error becomes 280 plumbing stack errors. Helonic found 47 misalignments across eight unit types before we locked the GMP. That's $210K we didn't have to bury in contingency.”
Frequently Asked Questions
How does Helonic handle repeating unit types in multifamily projects?
Helonic identifies repeating unit configurations and checks coordination consistency across all instances. When it finds a plumbing stack misalignment or fire separation inconsistency in one unit type, it reports the total impact across all floors and mirrored configurations — so you see both the root cause and the multiplied effect.
Can Helonic verify plumbing stack alignment across floors?
Yes. Helonic cross-references plumbing riser diagrams against structural slab penetration plans to verify that waste stacks, vent stacks, and water supply risers align through all floors. Misalignments between plumbing and structural drawings are flagged with specific location references.
Is Helonic useful during preconstruction specifically?
Preconstruction teams are one of the most common Helonic users. The analysis provides a data-driven basis for GMP contingency, helps identify design coordination issues that should be resolved before construction starts, and gives estimators a reliable count of anticipated RFIs and potential change orders.
How does Helonic check fire separation between residential units?
Helonic verifies that fire-rated assemblies between units are consistently detailed — same UL assembly reference, same materials, same penetration details — across all floors and unit types. It also checks that fire separation details at plumbing and electrical penetrations include proper firestopping callouts.
Next Case Study
General Contractor — Mixed-Use Development
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