Roof Recoverand Overlay

Roof recover — installing a new membrane system over an existing roof without a full tear-off — is an appealing option for Tacoma commercial building owners who want to extend their roof's service life while avoiding the cost and disruption of a complete system removal. On the right building with the right existing conditions, a recover is a legitimate 15- to 20-year solution. On the wrong building with wet insulation beneath the existing membrane, a recover is an expensive mistake that seals a deteriorating problem inside a new assembly. In the Pacific Northwest, where roofs accumulate wet insulation faster than dry-climate buildings, the moisture verification step before any recover decision is not optional.

Tacoma's sustained fall and winter rain — 42 inches annually with November and January as the peak months — gives moisture more opportunity to infiltrate a deteriorating membrane and saturate the insulation below it than most other U.S. markets. A TPO or EPDM roof that has been in service for 15 years with a history of minor lap seam delamination has likely allowed some water entry, and in the Pacific Northwest's cool, damp climate, that moisture does not dry out between rain events. It dwells in the insulation for months, spreading laterally through the insulation boards by capillary action. By the time the interior conditions are bad enough to cause a visible drip, the insulation saturation may extend well beyond the obvious leak location.

We conduct infrared thermal scans or nuclear moisture surveys on every building where a recover is being considered as an alternative to tear-off. The infrared scan is performed after sunset when the temperature differential between wet and dry insulation — wet insulation releasing stored heat more slowly than dry — creates detectable thermal signatures. We map the wet insulation areas against the total roof area and provide the owner with a percentage: under 10% wet insulation is a reasonable recover candidate; 10% to 25% requires targeted tear-out of wet sections before recovering the balance; over 25% wet insulation tips the cost-benefit analysis toward full tear-off because the wet material removal and replacement cost approaches the cost of a complete tear-off anyway.

Frederickson Industrial Center and Tideflats warehouse buildings are the most common recover candidates in the Tacoma market. These large-footprint, single-story buildings have roof areas that make tear-off cost-prohibitive relative to a well-executed recover on a dry substrate. A 150,000-square-foot Frederickson warehouse with dry insulation confirmed by a moisture scan is an excellent recover candidate — new recovery board over the existing membrane, mechanically attached or adhered new TPO or PVC, and 15 to 20 additional years of service life at a fraction of tear-off replacement cost. The same building with 40% wet insulation is not, and we tell owners that directly.

Building code layer count limits are a practical constraint on recover decisions. Washington State building code and most roofing manufacturer requirements limit commercial roofs to two membrane layers maximum in most configurations. A building that already has a recovered roof — an original BUR under an EPDM recover, for example — has reached its layer limit and requires a tear-off before a new system can be installed. We verify existing layer count during our initial inspection before proposing a recover, because a recover proposal that cannot be executed under code is not a proposal — it is a problem to discover at permit submission.

Recovery board specification for Tacoma recover projects takes into account the existing membrane condition as a substrate. An existing EPDM roof with surface oxidation and minor wrinkles requires a half-inch or quarter-inch recovery board to provide a smooth, stable substrate for the new membrane — the recovery board bridges over surface irregularities that would otherwise telegraph through a thin new membrane and create stress concentrations. On an existing TPO with a generally flat, sound surface, a thinner recovery board or, in some configurations, direct application over the existing membrane is possible, subject to manufacturer requirements for the new system.

Phased recover on large industrial buildings — completing the project in sections over multiple mobilizations — is a legitimate approach for owners who need to manage capital expenditure across budget years or who cannot accommodate a full-building roofing operation simultaneously. Each section must be properly terminated and water-tight at the end of each phase, with a clean transition detail at the boundary between the completed recover and the existing membrane awaiting its turn. We plan phase boundaries at natural roof breaks — expansion joints, parapet dividers, or structural bay lines — to ensure clean, maintainable terminations.

After a recover is complete, the owner has a new manufacturer warranty on the new system but not on the existing membrane below it. The existing membrane is now an interior component of a multi-layer assembly, and its condition at the time of recover becomes the baseline. Moisture scan documentation taken before the recover is the evidence that the substrate was dry at installation — that documentation protects the owner if a future moisture condition develops and raises questions about whether the wet insulation was present before or after the recover was executed.