Roof coating that keeps aging Jersey City flat roofs watertight

A coating is a restoration step for a roof that still keeps water out but is losing its surface. Think of a modified bitumen roof whose granules have worn thin, an EPDM roof turning chalky, or an aluminum-painted built-up roof that has gone dull and started to craze. The membrane underneath is still attached, the seams are mostly tight, and the insulation is dry. On a roof like that, a coating renews UV protection, closes small surface cracks and keeps the membrane working for a good stretch of years.

It is the wrong call when the roof is already wet inside. Water trapped in insulation or between plies keeps rotting the deck and will blister any coating laid over it. It is also the wrong call on a roof with seams failing everywhere, heavy ponding that never dries, or a deck that flexes underfoot. A roof with a few open seams gets targeted leak repairs first. One that is saturated across most of its area has reached the end of its life and needs replacing; a coating sold onto it is money spent twice.

You can't see wet insulation from the surface. A roof can look fine and still hold water in a few soft areas around a drain or along a parapet. So before we price a coating, we walk the roof, probe suspect areas and take small core samples where readings or soft spots suggest moisture. Each core is patched the same day.

If the survey finds a few wet sections, those get cut out, dried in with new insulation and membrane, and then the whole roof is coated. If it finds a large share of the roof is wet, coating stops making sense, and we'll show you the cores so you can see the problem yourself. That honesty matters on Jersey City walk-ups and condo buildings where several owners share the cost and need to understand why one plan was chosen over another.

The survey also tells us which coating chemistry fits. Some old roofs have been coated before, and not every product sticks to every other product. Silicone, for one, bonds poorly to almost anything except more silicone once it has weathered a few seasons. Asphalt-based roofs can bleed oils into some white coatings and stain them tan within a season, so on those we use a bleed-blocking base coat or a product made to sit over asphalt.

Coatings fail at the prep stage far more often than at the product stage. Dirt, soot, biological growth and loose granules all stop the coating from bonding, so we clean the roof thoroughly and let it dry. Any blisters are cut and repaired, loose seams are re-adhered, and the right primer goes down for the substrate, whether that's EPDM, modified bitumen, built-up or an older coating.

Next comes reinforcement. Seams, flashings, drains and penetrations get a detail coat embedded with polyester fabric before the field coats go on, because these spots move the most and crack first. Then the topcoat is applied in passes to a specified dry mil thickness, which we check with a gauge rather than guessing. Too thin and the coating wears through early; uneven and it fails first at the thin spots. On roofs with a lot of tired flashing, that reinforcement step does a big share of the real work.

A dark flat roof in a Jersey City summer gets very hot in strong sun, and the top-floor unit pays for it. A white reflective coating sends much of that heat back to the sky instead of into the ceiling below. Owners and tenants on the top floor of brick rowhouses and walk-ups often notice the difference in the first heat wave after the job, and the membrane underneath ages more slowly because it no longer bakes all afternoon.

Reflectivity drops as a white roof gets dirty, so a gentle rinse once a season helps. Aluminum coatings reflect well too, though less than a clean white finish, and they suit older built-up and asphalt-based roofs where some white products are a poor match. Drainage gets checked before the product is chosen, because a reflective finish under standing water for days loses its edge fast. Where water lingers, ponding water repair comes first, and our guide on how much standing water is too much explains the threshold.