Will bleach hurt my pavers?

Whether bleach hurts a paver depends on what the paver is made of, and the trade's documents answer that three separate times rather than once.

ICPI, the Natural Stone Institute and the Brick Industry Association each name a bleach use for their own material, and each ties it to particular stains or growth rather than to a general wash: ICPI's bleach lines are for leaf, wood rot, tobacco and smoke stains on concrete pavers; NSI's are for algae, moss and other biological stains on stone outdoors; BIA's cover organic growth, smoke and vanadium stains on brickwork. None of the three publishes a bleach strength for washing a whole paver surface, and none of the maker or association documents behind this answer says what bleach does to a sealer on top of the paver. The pressure and chemistry limits each material carries are laid out under concrete pavers, travertine and brick on the paver cleaning page.

On interlocking concrete pavers, ICPI ties household bleach to a short list of stains, not to a general wash.

For leaf, wood rot or tobacco stains, ICPI's remedy is to "apply household bleach and scrub with a stiff bristled brush." For a smoke stain, ICPI's entry reads: "Scrub with a poultice of talc with bleach diluted 1:5 with water. Rinse with water." That 1:5 belongs to a talc poultice on a smoke stain, not to a bucket for washing a driveway, and no ICPI line sets a bleach strength for a whole-surface wash.

None of those entries is a mold entry. Getting mold itself off a paver, as opposed to a leaf or tobacco stain, is a separate question, answered under whether mold can be removed from pavers.

Travertine and marble are calcareous stone, and the Natural Stone Institute's care guide, written for natural stone in general, is where their bleach lines sit.

NSI's line for stone around an outdoor pool, patio or hot tub is a clear-water flush, then a mild bleach solution against algae or moss, and its entry for biological stains such as mildew, lichens and fungi offers any one of ammonia, bleach or hydrogen peroxide, diluted in water. NSI puts the reason bluntly: "Do not mix ammonia and bleach. This combination creates a toxic and lethal gas." UF/IFAS Extension gives the same instruction in its own words: "Never mix ammonia and bleach."

Acid on this stone is a different matter from bleach, answered under whether travertine can be cleaned with acid.

On brickwork, BIA names bleach in more places than the other two bodies do: organic growth, general stains, smoke and one named stain, vanadium.

BIA says an exterior masonry surface that stays constantly damp encourages moss, algae, lichen or other microbial growth, and that masonry-cleaning makers offer biocides for it. "Applications of household bleach, ammonium sulfate or weed killer, in accordance with furnished directions, can also successfully remove organic material in some cases," BIA writes.

For stains, BIA writes that "in addition to proprietary cleaners, many stains can be removed by scrubbing with kitchen cleansers, bleach or other household chemicals"; for smoke it names scouring powder, particularly one containing bleach, with a stiff bristle brush; and it says sodium hypochlorite, the active ingredient in household bleaches, can be used on mild vanadium stains. Over all of it, for brickwork, BIA's principle is to select the gentlest effective cleaning method.

A cleaning solution reaches a planting bed two ways, by draining toward it or by overspray, and ICPI's plant lines were not written about bleach.

ICPI says to cover and protect all surfaces and vegetation around an area to be sealed, to anticipate where cleaning fluids will drain so they run across the pavement and not onto grass or vegetation, and, when strong acidic stain removers or cleaners might drain onto vegetation, to saturate the vegetation with water first. That pre-wetting line names acidic cleaners; ICPI publishes no line about bleach and plants. What ICPI does apply to every stain remover and cleaner is its own general line: read the label's directions and warnings, and follow them.

"Mold can grow on or fill in the empty spaces and crevices of porous materials, so the mold may be difficult or impossible to remove completely," the EPA says, and a concrete paver is a porous material. UF/IFAS adds that mildew spores are everywhere and that moisture and temperature govern their growth, so a treated patch can come back where the surface stays damp; the wet-season side of that is covered under why pavers go black through the summer.

Two surfaces near a paver bleach job have no bleach rule in the paver documents: the cured sealer on the pavers, and any laminated glass close enough to catch overspray.

None of the maker or association documents behind this answer says what household bleach does to a cured paver sealer. ICPI's instruction for any sealer is to consult its manufacturer or supplier about the environment the product will face, so a bleach question belongs with that maker.

Where the job sits beside a lanai, the glass carries a published caution of its own. The National Glass Association lists "Bleach (or other solutions containing sodium hypochlorite)" among materials that may harm laminated glass, and impact windows are built with laminated glass, so a bleach solution has to be kept off them. How impact glass is handled on the window side is laid out under impact and laminated glass types; the ingredients a roof wash publishes are listed under what a soft wash solution contains, and bleach on a roof is answered in the roof cleaning FAQ. Where paver rinse water may drain is set by the Naples water rules for paver cleaning.