What to expect during a roof replacement project.

There are many intricacies and complexities found during any construction project and roof replacements are no exception. Below are some steps and information owners should consider when considering a roof replacement project.

1. Pre-Project Planning: Assessment and Budgeting

Before undertaking a roof replacement, owners should conduct a roof condition assessment to determine whether full replacement is necessary or if targeted repairs will suffice. A qualified roof consultant or building envelope professional should perform a detailed inspection to evaluate:

• Current roof system condition (membrane integrity, insulation performance, and drainage issues)
• Existing warranty status (if applicable)
• Moisture infiltration risks.
• Structural capacity for new roofing materials.
• Building code compliance, especially in NYC and Boston.
  • Energy Savings and Sustainability
    • With New York City’s Local Law 97 and Boston’s BERDO 2.0, building owners must focus on energy efficiency and carbon footprint reductions. Reflective roofing, insulation upgrades, and photovoltaic-compatible membranes can contribute to compliance and cost savings. Consideration should be given to these aspects of the system during the planning and design phases.

These assessments will provide information such as material and system options as well as provide rough order of magnitude budgets. Ensure that the budgets provided at this stage include not only hard costs but soft costs such as material testing for asbestos containing materials (ACM), engineering & consulting costs, IR scanning and non-destructive testing (if necessary), permitting, expediting, bonds (if necessary) contingencies, etc. Other items that should be taken into account, but likely cannot be accurately budgeted by the building envelope professional such as lost opportunity costs or business interruption costs, security costs for overnight watches (if necessary).

Costs vary widely based on factors like roof size, system type, material selection, and necessary structural modifications. Time to perform the assessment can be anywhere for 2 weeks to 2 months considering the size and complexity of the roof.

2. Selecting the Right Roof System

In urban settings like NYC and Boston, low-slope roofing systems are the dominant choice for commercial buildings. Selecting the right system depends on factors like energy efficiency, durability, and compliance with local regulations. Some common Low-Slope Roofing Systems include the following:

1. Single-Ply Membranes (TPO, PVC, EPDM)
   • Advantages: Lightweight, energy-efficient, relatively fast installation.
   • Best for: Buildings requiring reflective roofing for cooling efficiency or flexibility in design.
   • Considerations: Proper detailing of seams and terminations is critical.
2. Built-Up Roofing (BUR)
   • Advantages: Long lifespan, multiple layers provide durability.
   • Best for: High-traffic rooftops or areas with heavy mechanical equipment.
   • Considerations: Requires skilled labor, longer installation time, typically not well suited for high rise construction due to a kettle being required.
3. Modified Bitumen Roofing
   • Advantages: Good impact resistance, flexible in cold climates.
   • Best for: High rise buildings that have high traffic.
4. Fluid applied roofing
   • Advantages: chemically bonded “seams”, easier to flash irregular penetrations, easy to maintain.
   • o Best for: Smaller roofs with lots of penetrations.

3. Design

Once the appropriate roof system is selected, the design can begin. Design often encompasses roof test cuts or cores. This is a process where a contractor is utilized to obtain information on the existing roof system(s) such as thickness, composition and roof deck type. This will inform later design decisions.

The design itself can take anywhere from 4-12 weeks. With some larger, more complex designs, several coordination meetings may be conducted to ensure the owner and design team are on the same page. Consideration should be given to the existing mechanical equipment on the roof, possible solar or green roof installation or amenity space upgrades

4. Permitting, Logistics, and Scheduling

Permitting Requirements

Both NYC and Boston have strict permitting and inspection requirements for roofing projects.

Key permits to secure:

• Work permits from the Department of Buildings (DOB)
• Sidewalk/street closures (if using cranes or dumpsters)
• Environmental compliance (especially if dealing with asbestos-containing materials (ACM))
• Appropriate fire permits for certain applications (torch, hot-kettle, etc.)

Scheduling Considerations

Expect about 4 weeks for permitting and material procurement before work begins. Weather-dependent scheduling is also crucial—late spring to early fall is ideal for roofing projects in the Northeast to avoid delays caused by snow and extreme cold. This means that the planning, design, and bidding process should begin in the late fall/early winter to take full advantage of the typical construction season.

5. Installation Process and Potential Disruptions

A commercial roof replacement can take several weeks to months, depending on size, complexity, and unforeseen site conditions. Here’s a step-by-step breakdown:

Step 1: Roof Tear-Off & Disposal

• Large dumpsters or crane lifts may be needed for debris removal. Certain owners will require risk mitigation plans prior to the placement of cranes, be sure to make the contractor aware of this prior to submitting pricing.
• Noise and vibrations could affect building occupants. If building operations are critical, off hours work may be considered, but is often an additional expense.
• Dust and debris are often created during the demolition process. If spray on fireproofing or insulation is used on the underside of the roof deck, additional dust may be created due to the vibration of the deck during the roof removal process. Debris shields or dust containment may be required by certain owners to ensure that building operations remain unaffected.
• Temporary waterproofing measures should be installed on a nightly basis, even if precipitation is not forecasted.

Step 2: Structural Adjustments (If Required)

• If insulation thickness needs to be increased (to meet current energy codes), door thresholds, parapets, and mechanical curbs and through wall flashings may need modifications. Vacuum insulated panels (VIPs) can mitigate the need for such changes but are not always feasible.

Step 3: Installation of New Roofing System

• Insulation layers (polyisocyanurate, extruded polystyrene, or VIPs) are installed.
• The membrane is laid and secured (either fully adhered or mechanically fastened).
• Flashings and drainage systems are finalized and any overburden systems are installed, if designed.

Step 4: Final Inspections & Closeout

• Roof manufacturers and consultants verify compliance with codes and manufacturer installation requirements.
• Owners receive as-built documentation, warranties, and maintenance instructions.

Timeline:
Overall from the investigation phase to the time that the contractor mobilizes can be anywhere from 10 weeks to 6 months. That time should be factored in by the Owner when considering budgeting for the soft costs and construction costs.

6. Post-Installation Considerations

Warranties and Maintenance
Owners should obtain:

• Manufacturer warranties (typically 15–30 years)
• Contractor workmanship warranties (usually 1–5 years)
• Ongoing maintenance plan to ensure longevity.

Routine inspections should occur at least twice a year (spring and fall), with special attention after major storms.

Final Thoughts

A roof replacement is a significant but necessary investment in the longevity and performance of a building. Owners in NYC and Boston must navigate unique challenges, from permitting and urban logistics to energy efficiency mandates. By working with qualified roofing consultants and contractors, budgeting appropriately, and understanding the step-by-step process, building owners can ensure a successful, code-compliant, and long-lasting roof replacement.

Kevin M. Duffy

Duffy Engineering

Principal