Reroof Strategy
A reroof is one of the largest non-revenue capital events a building will face, and most of the cost and most of the regret are decided before a single roll of membrane reaches the deck. When a project goes sideways, the cause is rarely the crew on the roof. It is a scope that never defined what was actually being bought: how much of the existing assembly stays, what the deck looks like under the insulation, which warranty terms govern, and who owns the risk when conditions differ from the proposal. Scoping a reroof the right way is owner-side work, and it begins long before bidding.
Start With What You Actually Have
You cannot scope a replacement for an assembly you have not characterized. The starting point is a documented existing-conditions investigation: core cuts taken across the roof to confirm the number of membrane plies, the insulation type and thickness, the presence of a vapor retarder, and the deck material below. A 1980s building may carry two or three roofs stacked on top of each other, each adding dead load and each hiding the next. A steel deck shows different failure behavior than a structural concrete or lightweight insulating concrete deck, and lightweight concrete in particular tends to hold trapped moisture that no membrane will outlast.
Pair the cores with a moisture survey, infrared or capacitance, to map saturated insulation that must come out regardless of the system selected. This is the single most common source of change orders: wet insulation discovered after the bid that the contractor priced around. If the survey is done up front and the wet area is quantified, that risk moves into the base scope where it belongs, rather than surfacing as a mid-project negotiation.
Recover or Tear Off
The recover-versus-tear-off decision drives budget, schedule, and long-term exposure more than the membrane choice does. A recover, installing a new system over the existing roof, is faster and cheaper and keeps the building dry during construction, but the building code generally allows only two total roof systems, and a recover is impossible if the existing field is wet or the deck is compromised. A tear-off removes everything to the deck, which is the only path to inspect and repair structural deck, reset slope, and start the warranty clock on a clean assembly.
We weigh several factors when advising owners on this fork:
- Number of existing roof systems already in place and what code permits
- Extent of wet insulation from the moisture survey, by percentage of field area
- Deck condition, fastener pull-out capacity, and any structural deterioration
- Whether the roof has adequate slope or needs tapered insulation to correct ponding
- Disposal and tipping costs, which can be significant on a built-up or ballasted roof
- The manufacturer warranty available over a recover versus a full tear-off
Selecting the System for the Building, Not the Catalog
Membrane selection should follow the building's use, exposure, and ownership horizon, not a contractor's preferred line. TPO and PVC are heat-welded thermoplastics with reflective surfaces that suit cooling-dominated climates and broad low-slope fields; PVC carries stronger chemical resistance and is the standard choice over restaurants and any roof exposed to grease or industrial discharge. EPDM, a black rubber sheet, performs well in cold climates and offers long, predictable field service but absorbs heat. Modified bitumen and built-up roofing remain appropriate for high-traffic roofs, plaza decks, and assemblies where redundancy matters more than reflectivity. SPF and coatings are restoration paths, not replacements, and only make sense on a sound substrate.
Just as consequential is the insulation and attachment specification: the R-value the energy code requires, the cover board that protects the membrane from foot traffic and hail, and the attachment method, fully adhered, mechanically fastened, or ballasted, which must be engineered to the building's wind uplift zone. A membrane is only as good as what holds it down in a storm.
Write the Warranty Into the Scope
The warranty is a procurement decision, and owners routinely under-specify it. A manufacturer's material warranty covers only the membrane; an NDL (no dollar limit) system warranty covers labor and materials for the full assembly and is what an asset owner should require. The terms that matter are the duration, whether ponding water voids coverage, wind-speed limits, and the inspection that the manufacturer's technical representative performs at closeout. That manufacturer inspection is leverage: it is a second set of eyes confirming the installation meets the spec before you accept the work and release final payment.
Require that the warranty be issued in the building owner's name and confirm it is transferable, since a non-transferable warranty quietly erodes asset value at sale. The scope should obligate the contractor to deliver the executed warranty, the as-built details, and the closeout package as a condition of final payment.
Control the Bid So You Compare Like for Like
The fastest way to overpay or to buy a thinner roof than you intended is to issue a vague request and let three contractors each interpret it differently. A disciplined scope specifies the system by manufacturer and product, the insulation R-value and cover board, the attachment method, the metal and flashing details, and the warranty class, so that every bid prices the same building. Allowances should be carried for deck repair and wet insulation replacement at a stated unit price, which neutralizes the most common change-order leverage.
Done this way, the bids become comparable, the low number is a real number, and the project that gets built is the project that was scoped. The reroof you regret is almost always the one that was priced before anyone knew what was under the membrane.
Protect the Building Below and the Schedule Around It
A reroof does not happen in isolation. Tenants occupy the space below, rooftop equipment must keep running, and a single uncovered night during a tear-off can flood an interior. The scope should spell out daily dry-in requirements so no section of deck is left exposed to weather, define how the contractor protects HVAC units and live penetrations, and establish staging and crane locations that do not strand tenant parking or block egress. On occupied buildings, sequencing the work over the field in manageable sections, rather than opening the whole roof at once, is the difference between a controlled project and a water-damage claim.
Schedule and weather belong in the scope as much as materials. Thermoplastic seams welded in marginal temperatures and adhesives applied to damp decks are known failure points, so the specification should state the conditions under which work may proceed and require the contractor to carry the risk of redoing work compromised by weather. Tie milestone and final payments to documented dry-in, the manufacturer's closeout inspection, and delivery of the warranty package. A reroof scoped with this much discipline costs more hours to prepare and far fewer dollars to live with, and it is the version of the project an owner can defend to ownership, to a lender, and to the next buyer.