On a commercial flat roof, the expensive decision is not which membrane to buy. It is whether the old roof comes off first. A recover installs the new membrane over the existing system and saves 30 to 40% of replacement cost; a tear-off strips the roof to the deck and resets everything, at full price. Owners lean toward the recover for obvious reasons, and it is often right. It is wrong often enough, and expensively enough, that we do not answer the question from the parking lot. Four conditions decide it, and the commercial roofing page covers the systems themselves; this page covers the decision.
Condition one: the insulation is dry
This is the condition that kills recovers, and it is invisible from above. Insulation under a flat roof gets wet through old seam failures, failed penetrations, and years of ponding, and a new membrane over wet insulation traps the moisture permanently: the insulation loses its R-value, the deck below it corrodes or rots, and the new roof fails from underneath within a few years. So the recover decision starts with a moisture survey. An infrared scan after sunset shows wet areas as warm patches, because water holds heat longer than dry foam, and core cuts at the suspect spots confirm what the scan suggests. Small wet areas can be cut out and replaced before a recover; widespread saturation means the insulation comes out, and once it is coming out, the tear-off is already most of the way done.
Condition two: there is only one roof up there
Building codes allow one existing roof system under a new one and no more. A building that has already been recovered once has two layers, and the next roof has to be a tear-off. This is worth checking on the older commercial blocks downtown, where a built-up tar-and-gravel roof from the building’s first life often has a modified bitumen or single-ply recover over it already. The layer count comes from a core cut, not from the owner’s memory.
Condition three: the structure can take the weight
A recover adds weight: the new membrane, a cover board over the old surface, and in some cases new tapered insulation to fix drainage. On a modern steel-deck building that is nothing. On an older wood-framed roof that already carries a built-up system, gravel, and rooftop equipment, plus a Wisconsin snow load every winter, the added dead load is a structural question, and the answer comes from the building’s drawings or an engineer, not from us. When the structure is marginal, the tear-off is the safer choice because it removes weight instead of adding it.
Condition four: the existing membrane is sound and attached
The new roof is only as flat and as attached as what is under it. A recover goes over a membrane that is dry, adhered or fastened, and free of widespread blistering, alligatoring, or seam separation; a cover board (gypsum or high-density polyiso) bridges minor surface problems and gives the new membrane a clean substrate. A membrane that is delaminating, bubbling across the field, or pulling away from the edge metal in several places is telling you the system underneath has failed, and a recover over it fails with it.
The energy code, and why it moves the price
Wisconsin’s commercial energy code follows the national standard for roof replacement: when a tear-off exposes the roof insulation, the insulation has to be brought up to the current minimum before the new membrane goes on. On a building insulated in the 1980s that can mean doubling the insulation, which is a real cost line and a real drop in the heating bill afterward. A recover does not expose the insulation, so it does not trigger the requirement. That difference is a large part of the 30 to 40% gap between the two paths, and it is the reason a tear-off quote on an old building comes with an insulation line that the recover quote does not have.
The math: cost, life, and how long you will own the building
| Recover | Tear-off and replace | |
|---|---|---|
| Cost | About 30 to 40% below replacement | Full price; includes disposal and the energy-code insulation upgrade |
| Service life | Typically 15 to 20 years | 25 to 30 years on a known-quantity system |
| Disruption | Faster, little debris, the business stays open | Tear-off noise and dust on the floor below; containment for medical, food, or sensitive inventory |
| Warranty | Manufacturer system warranty available when the cover board and spec are followed | Full system warranty |
| Conditions | Dry insulation, one existing layer, adequate structure, sound membrane | None: the roof resets |
Cost per year of life is where the decision usually lands. A recover at 60 to 70% of the price for roughly two-thirds of the life is close to a wash on paper; it wins when the owner plans to sell or redevelop inside the recover’s life, when the budget will not stretch to a tear-off this year, or when the building needs to stay open without interruption. The tear-off wins when the insulation is wet or thin, when the building will be held for decades, or when the second layer is already up there and the code has made the choice.
Two more lines belong in the conversation with your accountant. A full replacement is typically a capital expense depreciated over 39 years for nonresidential property, while maintenance is deducted in the year it is incurred; where a recover falls depends on its scope, and the answer changes the after-tax cost. And some carriers refuse renewal on roofs past 20 years without a recent inspection or replacement, which puts a hard date on a decision that would otherwise drift.
How we decide it on your roof
The free roof asset assessment on the commercial page is where this starts: system identification, the layer count, drainage, penetrations, and a written recommendation. When a recover looks possible, the moisture survey and core cuts follow before any quote is written. You get both numbers, recover and tear-off, with the conditions spelled out, and the same crew does either one.