Does sealing help pavers hold their joint sand?

Read the institute's own sentences closely and the claim stays small: secondarily, some stabilization, can help maintain, never a plain yes.

ICPI Tech Spec 5 puts the effect in one clause: “Since liquid sealers penetrate the joint sand to some extent during application, they secondarily provide some stabilization.” In its list of what sealers are useful for, it adds that they “can help maintain the sand in the joints under high velocity water flows.” The same list says sealers “can stabilize joint sand between pavers cleaned by vacuum equipment,” and that sentence carries its condition with it: it is about pavers cleaned by vacuum equipment, not a general promise for every sealed joint.

A joint sand stabilizer is a different product with a different primary job, and ICPI describes it in separate sentences; what that category covers is on the joint stabilization glossary page.

In ICPI's account a sealer holds sand as a by-product of soaking in, which is what the word secondarily means.

Tech Spec 6, the CMHA maintenance guide, describes the same effect in its own words: “Sealers can also help hold the sand in the joints. These are applied over the entire paver surface as a liquid and allowed to soak and cure in the joints.” A paver that has already shifted is a different matter, answered on whether sealing fixes loose pavers.

The sand a sealer reaches sits at the top of the joint, just below each paver's chamfer, the beveled top edge, which is where a liquid spread across the surface runs down into the joint.

Beyond ICPI's general line, the makers split their own products, and only a specific product's label says which side it is on.

SEK-Surebond describes SB-1300 as a water-based acrylic co-polymer “sealer and joint sand stabilizer” in one. Seal 'n Lock claims its Super-Wet-Look gives “superior joint stabilization (for paver joints up to ¼” in width), no need for polymeric sand.” Techniseal heads its Natural Look (NS) Protector data sheet “SEALER & JOINT STABILIZER - ALL IN ONE,” and the same data sheet says the maker's Natural Look (iN) Protector “can also be an alternative although it is not a joint stabilizer.” One maker, two products, two answers on one sheet.

How long a stabilizer lasts is a question ICPI routes to the maker: “Given the wide range of joint sand stabilizers and proprietary formulations, it is best to consult with the manufacture to determine expected lifespan and/or reapplication rates.” ICPI publishes no general figure, so the manufacturer of the specific product is the one to ask.

The products sold for joints come at the same problem from the other end.

ICPI: “Liquid stabilizers bind the sand in the joint and secondarily provide sealing of the concrete paver surface.” A sealer's first job is the paver face and the sand comes second; a liquid stabilizer's first job is the sand and the face comes second.

What sits in the joint differs too. ICPI's glossary defines joint sand as “sand swept into the openings between the units,” while SEK-Surebond's data sheet defines its PolySweep polymeric sand as “a blend of native sands conforming to the ASTM C-144 standard, and polymer binders that once activated allow the joints to expand and contract with the elements.” The order in which sand and sealer go in, with the drying condition SEK-Surebond attaches to each order, is set out on how paver sealing works.

None of the above is a rule that every joint needs treating, and none of it reaches sand that has already washed out.

Whether a joint needs stabilizing at all is a separate question, and ICPI's own answer, that stabilization is generally optional, is quoted in the joint sand and rain section of the paver cleaning page. What ICPI credits a sealer with is sand still in the joint, which the liquid penetrates as it goes on; sand that has already washed out is not something a sealer puts back.

What makes sand leave a joint, and what the trade does about it, is a separate question, answered on why paver joint sand washes out.