Roof Coating in Southfield, MI

Silicone is the coating for roofs that hold some water. Western Colloid, a coating manufacturer, writes that silicone coatings can sit in ponding water, while acrylics may curl or peel there. That doesn't make ponding harmless. The same article warns the membrane underneath may not hold up even when the coating does. Henry's installation instructions for its silicone system show how much prep comes before the first coat: the contractor must verify the old roof is dry and leak-free, run adhesion tests (primer if a test comes in low), and replace any wet insulation found in the survey.

Acrylic coatings are water-based and stretch with the roof as it heats and cools. Western Colloid's article says they stand up to heavy rain as long as the roof drains properly. That makes them a match for roofs with some pitch and working drains. Being water-based, an acrylic needs a dry stretch of mild weather to cure, which narrows the season here. On a roof where water sits in the low spots for days, it's the wrong product.

Aged rubber and modified bitumen roofs can be coated if the sheets are still attached and the insulation is dry. The prep differs by surface. Henry's silicone instructions call for adhesion tests on smooth surfaces, with a minimum pull strength, and a primer and retest if a test fails. Granulated modified bitumen doesn't need the test. Seams and laps get reinforced before the field coat goes on, and old mastic patches come off, because a coating bonds to whatever is under it, including the patch that's already failing.

On exposed-fastener metal roofs, the screws and their rubber washers are the usual weak point, so restoration starts there. Henry's instructions say to tighten fasteners and replace loose ones with larger-diameter screws. Rust is cleaned down to a smooth surface, and seams and fasteners are pretreated before the full coat. One budgeting detail from the same instructions: ribbed metal has more surface than its footprint, so coating quantities get a 15 to 30 percent stretch factor. A quote that prices metal by the flat square footage is short.

Spray-on "rejuvenators" for asphalt shingles get marketed hard, so here is the industry position. The Asphalt Roofing Manufacturers Association strongly advises against field-applied coatings or rejuvenators on installed shingles. It says they may affect the roof's fire classification, algae resistance and impact resistance, that there's limited documentation of their benefits, and that many need repeat applications. Check with your shingle manufacturer before you spend money on it. If the shingles are near the end of their life, a roof inspection will tell you whether repair or replacement is the honest answer.