Joint stabilization

ICPI's own glossary names exactly two kinds of joint sand stabilizer, and they reach the sand in different ways.

A liquid penetrating stabilizer, in the glossary's terms, is a polymer liquid spread over the surface of the pavers and allowed to soak into the joint sand, which it stabilizes once it cures. Tech Spec 5 adds that liquid stabilizers bind the sand in the joint and, secondarily, seal the paver surface. A dry mix stabilizer is joint sand treated with chemicals that water activates to bind the sand particles together. Tech Spec 5 describes those additives as “organic, inorganic, or polymer compounds that stiffen and stabilize the joints when activated by water applied to the joint sand.”

Either kind is there to cut the risk of joint sand being carried off once it is in place. A sealer can do some of the same work, and how much it does is worked out on whether sealing helps pavers hold their joint sand.

For many paver surfaces ICPI treats stabilization as optional, because joint sand tends to settle in without it.

Tech Spec 5 says sand in joints will likely stabilize over time as silts and other fines work into the spaces between the grains, and Tech Spec 6 adds that sediment and debris from traffic settle into the tops of the joints and help hold the sand.

The exceptions carry different verbs, and the verbs matter. ICPI says stabilization “is recommended on high slope applications over 7%.” Pavements with regular, heavy rainfall and surfaces with concentrated water flow at drip lines are ones it says can benefit or will better resist erosion, lines quoted in full under joint sand, weeds and the Naples rain. In residential applications, it says stabilization at downspouts and under eaves helps keep joint sand in place. Tech Spec 6 calls steep slopes, concentrated surface water flow and continually windy areas “good candidates for joint sand stabilization,” and Tech Spec 5 notes that tumbled pavers may require stabilized joint sand if they have slightly irregular sides and wide joints.

ICPI puts one condition in front of a liquid stabilizer and one limit on every stabilizer.

Tech Spec 5 says liquid and dry applied stabilizers are not a substitute for recommended installation practices, and that every liquid stabilization product needs the joint sand compacted and consolidated in the joints until full before it goes on. Stabilizers resist many of the conditions that wear a paver surface down in use, but ICPI gives them no credit for structural, load-bearing strength. Loose pavers are a different matter, taken up on whether sealing fixes loose pavers.

Why sand leaves a joint in the first place is covered on why the sand is washing out of paver joints, and where weeds in those joints come from is on whether weeds grow up from underneath pavers. When Tech Spec 6 describes topping joints back up, it fills them to the bottom of the paver's chamfer, the beveled edge around its top.