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MEP Redesign
10, Jun 2025
Top 5 MEP Redesign Mistakes to Avoid in Tenant Improvement Projects

Introduction

Tenant Improvement (TI) projects breathe new life into existing commercial spaces, aligning them with a tenant’s unique operational needs. However, poorly planned mechanical, electrical, and plumbing (MEP) systems often derail timelines, inflate budgets, and frustrate both owners and tenants. In fact, avoiding the most common MEP redesign mistakes can save weeks of rework and tens of thousands of dollars. In this post, we’ll explore the top 5 MEP redesign mistakes in TI projects—why they happen, the consequences, and actionable steps you can take to prevent them. By the end, you’ll understand how to streamline your TI’s MEP scope and deliver a high-quality, code-compliant space on schedule.

Focus Keyphrase (“MEP Redesign Mistakes in TI Projects”) appears in the title, introduction, subheadings, and conclusion for SEO.

Objective: Help facility managers, property owners, architects, and contractors understand and avoid the five most costly MEP redesign mistakes during TI projects.
Target Audience: Commercial real estate owners, property managers, general contractors, architects, and anyone responsible for coordinating TI work.
Desired Action: Encourage readers to implement proactive MEP review steps and engage an experienced MEP design team (like GDI Engineering Design’s MEP Services) early in the TI process.


1. Incomplete Existing System Assessment

Why It Happens

Many TI teams treat MEP design as an afterthought. They rely on outdated as-built drawings or building owner’s recollection instead of verifying on-site conditions. As a result, critical dimensions, equipment locations, and hidden conflicts go unnoticed.

Consequences

  • Costly Rework: Discovering that ductwork must be rerouted under an unmovable beam or that plumbing lines don’t match the drawing forces demolition of new finishes.
  • Unplanned Delays: When contractors uncover mismatches—like an electrical panel tucked behind a gypsum wall—they halt construction until a redesign is complete.
  • Tenant Dissatisfaction: Tenants expect a turnkey space. If MEP systems fail to support new equipment loads, occupants endure temperature swings, electrical interruptions, or low water pressure.

How to Avoid It

  1. Perform a Detailed Field Verification: Engage an MEP professional to walk the entire space and record dimensions, equipment serial numbers, and ceiling heights. Use laser measurement tools and high-resolution photos.
  2. Review Multiple Sources, But Verify On-Site: Compare facility drawings, landlord’s documentation, and previous TI records. Treat each source as a guide, not gospel.
  3. Coordinate a Joint Site Tour: Schedule a walkthrough with the general contractor, architectural team, and key MEP subconsultants before starting the design. This ensures everyone sees existing conditions simultaneously.
  4. Include Core Drilling or Scanning if Necessary: In older buildings, hidden duct chases or cast-in-place beams can mask real dimensions. Use non-destructive scanning or drill small cores to confirm ceiling thickness and piping routes.

By fully documenting existing MEP systems, you eliminate most “unknown conditions” that lead to late-stage redesigns.


2. Neglecting Accurate Load Calculations

Why It Happens

Owners often assume that the existing HVAC, electrical, and plumbing capacity will suffice for the new tenant program. TI designers may reuse previous load calculations or omit a thorough reevaluation—especially when the tenant’s planned occupancy density, computer loads, or specialty equipment differ from predecessors.

Consequences

  • Overloaded Electrical Infrastructure: An outdated load analysis can allow 60 new workstations or a coffee bar to trip breakers, forcing a costly utility service upgrade.
  • Insufficient HVAC Capacity: Ignoring fresh air requirements and increased heat gains from lighting or equipment results in poor temperature control, uncomfortable employees, and reduced productivity.
  • Under-sized Plumbing: Adding restroom fixtures or relocating kitchens without recalculating fixture unit counts leads to low flow rates, code violations, and tenant complaints.

How to Avoid It

  1. Conduct a Comprehensive Electrical Load Study: Follow the National Electrical Code (NEC) Article 220 to calculate connected loads—computers, receptacles, lighting, and specialty equipment. Include demand factors and scenarios for peak loading.
  2. Perform a Detailed HVAC Heat Gain/Loss Analysis: Use Manual J (for small‐scale spaces) or full‐building load calculation software (e.g., Carrier HAP, Trane Trace) to size air handling units, terminal devices, and ductwork for the new tenant’s occupancy profile.
  3. Verify Plumbing Fixture Unit Requirements: Reference the local plumbing code—often based on the Uniform Plumbing Code (UPC) or International Plumbing Code (IPC)—to determine required drain sizes and water supply lines. Even a single added sink or mop station can alter pipe sizing.
  4. Coordinate with Tenant’s Furniture and Equipment Layout: Request floor plans, equipment cut sheets, and appliance power ratings early. For example, if the tenant installs a microwave, kitchenette, or server rack, factor those loads into your calculations.

By validating new loads for electrical, HVAC, and plumbing, you ensure the MEP design will support tenant operations without costly last-minute upgrades.


3. Lack of Interdisciplinary Coordination

Why It Happens

In many TI projects, architecture, structural, and MEP disciplines operate in silos. Architects finalize partitions and finishes before MEP consultants are fully engaged. This sequential workflow often results in clashes between duct runs, conduit, plumbing risers, and new walls or ceilings.

Consequences

  • On-Site Clashes: HVAC plenum space may conflict with new fire sprinkler branches or electrical cable trays. Once drywall is framed, rerouting MEP systems means cutting into finished work—both expensive and disruptive.
  • Reduced Ceiling Heights: Late-added mechanical equipment may require a deeper plenum, forcing a lower finished ceiling. This impacts design aesthetics and may violate headroom requirements.
  • Wasted Material and Labor: Contractors produce shop drawings only to find that they don’t fit. This leads to reorders, scrap, and extended field coordination—each adding to project cost.

How to Avoid It

  1. Adopt a 3D BIM Coordination Process: Even for smaller TI scopes, a basic Revit model or Navisworks clash detection can identify conflicts between MEP runs and architectural elements. Visualizing systems in three dimensions reduces on-site surprises.
  2. Host Regular Interdisciplinary Design Meetings: Schedule weekly touchpoints where architects, structural engineers, and MEP designers review the latest drawings together. Discuss upcoming changes in partitions, ceiling heights, or structural modifications.
  3. Freeze Architectural Layouts Before Final MEP Routing: Lock down wall locations, ceiling grids, and major structural elements before finalizing MEP pathways. Any architectural move after MEP routing multiplies coordination effort.
  4. Assign an MEP Coordination Lead: Designate a team member responsible solely for cross-discipline checks. This coordinator tracks issues, compiles RFIs, and ensures design updates are communicated to all parties.

When teams collaborate in parallel—sharing models and attending coordination sessions—TI projects proceed more smoothly and avoid expensive clash fixes.


4. Underestimating Code and Permit Complexities

Why It Happens

Tenant Improvement work often triggers significant code requirements, yet some teams treat it like a light cosmetic job. They assume preexisting code compliance will carry over or that minor in-suite changes qualify for a simple permit. In reality, TI projects commonly demand full fire, accessibility, and energy-code reviews.

Consequences

  • Extended Permit Review Times: Submitting drawings missing required fire-resistive assemblies around new penetrations or lacking ADA-compliant restroom details can delay approvals by weeks.
  • Field Change Orders: Inspectors may require additional fire stopping, exit signage, or emergency power modifications, causing mid-construction rework.
  • Increased Soft Costs: After-the-fact code compliance (adding sprinklers, upgrading insulation, or modifying electrical service) escalates budget and can jeopardize project profitability.

How to Avoid It

  1. Engage a Code Consultant Early: A dedicated code reviewer (or in-house expert) can catch issues—such as corridor width reductions, exit path modifications, and energy-code compliance under ASHRAE 90.1 or local ordinance.
  2. Perform a Preliminary Code Analysis Before Design: Identify key requirements—fire ratings for shaft walls, occupant load calculations, required egress widths, and restroom fixture counts—so design teams incorporate them from day one.
  3. Coordinate with Local Building Departments: If your TI scope is unusual (e.g., converting a mezzanine), request written interpretations from the jurisdiction to clarify ambiguous code sections.
  4. Budget and Schedule for Plan Check: Factor in realistic permit review times—often 20–30 business days for commercial TI submissions. Include contingency for resubmittals if plan reviewers request revisions.

Proactively addressing code compliance guarantees your TI design is complete when you submit for permits, preventing last-minute scope increases.


5. Skipping Thorough Shop-Check and Coordination Drawings

Why It Happens

To save time or reduce fees, some project teams ask contractors to handle MEP coordination “in the field,” accepting hand-sketched layouts or verbal instructions. This approach assumes minor adjustments can be resolved on site without detailed shop-drawings.

Consequences

  • Frequent RFIs (Requests for Information): Without clear coordination drawings, contractors submit dozens of RFIs to clarify pipe hanger locations, clearance requirements, or routing through tight spaces—each RFI momentarily halts work until resolved.
  • Increased Material Waste: Ordering conduit, duct, or pipe without finalized routing leads to excess scrap or reordering when designs shift.
  • Extended Construction Schedule: Every unanswered question on the job site translates into downtime. Cumulatively, these delays can push out milestone dates and jeopardize tenant move-in.

How to Avoid It

  1. Require Detailed MEP Coordination Drawings: These drawings should overlay proposed ductwork, conduit, and piping on reflected ceiling plans. Show exact dimensions, support spacing, and clearance to structural elements.
  2. Hold a Formal Shop-Check Review: Before fabricating duct, pipe, or conduit, convene mechanical, electrical, and plumbing contractors in a “shop-check” meeting with design engineers. This group review ensures everyone agrees on routing, hanger spacing, and equipment clearances.
  3. Include Installation Tolerances and Notes: Specify how much tolerance is allowed around piping penetrations, required clearances around electrical switchgear, and headroom under ductwork. Clear notes reduce guesswork.
  4. Maintain a Centralized Document Repository: Use a cloud-based system (such as BIM 360, Procore, or PlanGrid) so that any revisions to the coordination drawings immediately push out to all team members—architects, engineers, and contractors.

Investing time in thorough shop-checks avoids material scrap, RFI backlogs, and schedule overruns—keeping the TI project on budget and on time.


Conclusion

Tenant Improvement projects present unique challenges whenever MEP systems are involved. Unfortunately, many TI teams discover “MEP redesign mistakes” too late: missing load calculations, unverified existing conditions, siloed workflows, code surprises, and insufficient coordination all contribute to costly rework and project delays.

In summary, you can avoid these pitfalls by:

  • Performing a detailed existing condition assessment
  • Conducting accurate load calculations for electrical, HVAC, and plumbing
  • Implementing interdisciplinary coordination through BIM and regular design meetings
  • Proactively addressing code and permit requirements before design finalization
  • Insisting on thorough shop-check and coordination drawings before fabrication

By following these best practices, you’ll reduce budget overruns, minimize schedule risks, and deliver a fully functional, compliant TI space. If you’re planning a TI project in California, Texas, or beyond, consider engaging an experienced MEP partner like GDI Engineering Design’s MEP Services. Our team combines rigorous field verification, precise load modeling, and disciplined coordination—ensuring your project proceeds smoothly from concept to occupancy.


Internal Links

  • For an overview of our full MEP design capabilities, see MEP Engineering Services.
  • Learn how we integrated complex systems in a recent TI at our Office Renovation Case Study.

External Links

  • Review ASHRAE’s HVAC design standards: ashrae.org
  • See NEC Article 220 for electrical load calculation requirements: NFPA

Ready to avoid the top 5 MEP redesign mistakes in your next TI? Contact GDI Engineering Design today for a comprehensive MEP assessment, and let our experts guide you from initial field verification through final shop-check.

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