Can algae come back after sealing?

The sequence runs clean, then seal, and the second step has a narrower job than many owners expect.

ICPI's own verbs are about intrusion and staining, not growth: "Sealers reduce the intrusion of water, stains, oils and dirt into the paver surfaces," and elsewhere ICPI says sealers resist stains. Reduce and resist, not stop; what soaks in, not what grows on top.

ICPI's growth-related lines for sealers are about weeds and insects, and they place them in the joints, not on the face: joint and stabilization materials, like sealers, "reduce the potential for weeds and insects in the joints." That is the joint sand argument covered under joint sand, weeds and the Naples rain, and whether a seal keeps weeds out at all is answered under whether sealing stops weeds. None of ICPI's sealer lines names algae, mold or any growth on the surface itself.

Once the seal is on, the next rain puts water back on top of the surface, and the top of the surface is where algae and mold grow.

The EPA's rule for mold applies to whatever sits on a paver, sealed or not: "The key to mold control is moisture control," and "the mold spores will not grow if moisture is not present." Nothing in ICPI's sealer lines claims to change that, and a sealer does not keep spores or leaf litter from landing on the paver in the first place.

Why dark growth builds through the wet season is covered under why pavers darken over the summer, and getting growth off again is answered under whether mold can be removed from pavers. A sealed surface that simply collects dirt again is its own question, under whether sealed pavers still get dirty.

Techniseal's product guide does not claim that its paver protectors keep algae off the surface.

Techniseal describes its concrete paver protectors as protection "against weathering and the penetration of contaminants," and the product it names for moss and mildew is a different one, its Organic Stain Remover: a cleaner, not a protector.

The nearest published line on recurrence is written for roofs, not pavers. Of bleach-and-water cleaning of algae on asphalt roofing, ARMA says: "The effectiveness of such cleaning is only temporary, and the discoloration may recur." That is a roof statement and is not carried over as a paver finding; on pavers, the reason growth returns is the moisture the EPA names. More answers on paver cleaning and sealing cover what a sealer does and does not change.