Projects
require seamless integration of multiple disciplines, including architectural,
structural, and MEP (Mechanical, Electrical, and Plumbing) systems. However, this complexity often leads to
design conflicts, commonly known as clashes.
If not detected early, these clashes result in expensive rework, delays,
and material & labour waste, significantly inflating project costs.
Studies have highlighted the significant
financial burden of clashes in construction projects. Like, rework and material waste due to
clashes can account for up to 30% of project costs. On average, each unresolved clash may cost
approximately $1,500+. These clashes can
result in significant financial losses when taken as a whole, highlighting the
significance of proactive clash detection and resolution in project management.
Common
Causes of Clashes in Construction
1.
Interdisciplinary Conflicts
Conflicts
arise when the architectural, structural, and MEP systems clash after
progressing to LOD 300-350, when models are enriched with system-specific
details like hanger placements, insulation, clearances, and equipment access.
Even with individual discipline-specific
modeling done correctly, combined trade coordination often reveals overlooked
spatial and functional conflicts, especially when designs are translated into
construction-level details.
The structural team places transfer beams
below a mechanical room to support large equipment loads. However, the MEP team has already routed
primary HVAC ducts and large diameter piping directly through this zone,
assuming a clear soffit based on the previous design.
Such conflicts typically surface after trades
begin detailed coordination—this is too late for design changes to happen
seamlessly, and often results in expensive structural revisions, resequencing
trades, and fabrication delays
2. Spatial
Overlaps (Component Buffer Clashes)
These
clashes are not about obvious overlaps—but rather about clearance, maintenance
access, and constructability issues that arise in congested zones when shifting
from design intent to real installation.
At LOD 350/400, systems include real-world
details like hanger supports, insulation thickness, prefabricated spools, valve
access panels, fireproofing layers, and ceiling substructure. This level of detail reveals erroneous
spatial assumptions made in earlier stages of design. A prefabricated duct
riser is modeled to pass through a shaft, but the actual size, insulation
thickness, and seismic bracing requirements leave no clearance for the adjacent
fire riser and electrical tray.
This is a frequent clash type in hospital
projects, data centers, and high-density mechanical rooms, where space is
extremely tight, and equipment access for maintenance is mandatory. Rework is required and project delays result
as a result of the disruption to pre-fabrication workflows.
3.Workflow
Sequencing Issues (Construction Timing Conflicts)
Even if
clash detection is done well, poor trade coordination at the site level causes
on-site clashes because systems are installed out of sequence or using
different layouts than what the model shows.
When MEP subcontractors work with shop
drawings that are slightly disconnected from the federated model, installation
teams sometimes ‘adjust on the fly’, leading to as-built conditions that clash
with other trades’ work.
The fire sprinkler contractor installs piping
runs before structural embeds for ceiling hangers are placed, requiring later
rework where piping obstructs embed locations.
4.Lack of
Communication between Teams
Because correcting work often involves
physical demolition, re-pouring of concrete, or voiding inspector
pre-approvals, these sequencing conflicts typically do not become apparent
until LOD 400 installation coordination meetings—all of which drive up costs.
With multiple revisions happening during construction, not all changes make it
back into the coordinated BIM model, especially for minor field
adjustments. Over time, these
undocumented changes snowball into larger constructability clashes.
Last-minute RFIs, product substitutions, and
site-driven changes frequently bypass the formal update cycle even with a
common data environment (CDE). The MEP contractor uses a pre-insulated ductwork
system because of the long lead times. However, the new insulation thickness
makes it harder to clear the ceiling, which was not told to the electrical
team, whose conduits were planned for the same ceiling space. This is a classic
clash type in large, phased projects (hospitals, airports, high-rises), where
overlapping trades and constant updates create an environment where what’s on
paper no longer matches reality on-site.
This breakdown triggers rapid-fire RFIs, out-of-sequence rework, and
schedule compression, leading to quality risks.