Does sealing make pavers waterproof?

Reduce is the verb ICPI's Tech Spec 5 chooses. A sealer cuts down how much water and staining gets into the paver surface, and ICPI says it is applied to add further protection, which is a different promise from sealing the surface shut.

Silane and siloxane sealers create what ICPI calls a hydrophobic barrier to moisture, one that keeps moisture from entering while still letting the concrete release water vapor. Techniseal's Product Guide says its Protectors are microporous and let moisture out. SEK-Surebond says its SB-1300 “is breathable and will not trap naturally occurring moisture and efflorescence.” The same sheet warns that excessive applications may decrease breathability. ICPI goes further: a sealer that is not breathable is one of the four conditions it lists for a sealed paver turning white.

Waterproof describes a barrier that holds in both directions; breathable describes one that lets vapor out. A paver sealer built to breathe is not trying to be the first thing. What else the word sealer does not promise, and the application limits that come with it, are under the limits of the word sealer.

Two guides written for two different materials land on the same qualifier.

ASCC, writing about concrete sealers, says sealers are “scratch and stain resistant,” not “scratch and stain proof,” and that “Sealers will help prevent but not eliminate stains.” The Natural Stone Institute draws the same line for stone: sealing leaves it more stain resistant, not stain proof. Neither reaches for waterproof.

Techniseal's own FAQ makes a narrower claim for its Protectors: if pavers are sealed, stains remain on the sealant rather than reaching the paver pores. That is a maker's claim for its own product line, not a general rule, and whether it amounts to hiding a stain already on the surface is answered under will sealing hide stains on pavers. Film-forming and penetrating sealers, the two families a paver sealer comes in, are compared under sealing on the paver cleaning page.

Techniseal does sell a product it names a waterproofing sealant, and the name is the point: it sits outside the paver Protector line.

Its Brick and Concrete Waterproofing Sealant is marketed for facades, mortar joints and decorative stone, not for a paver driveway or patio. That name belongs to one product, not to paver sealer in general.

Whether a sealed surface is easier to keep clean day to day is a related question, answered under are sealed pavers easier to clean.