Note: If you’d prefer to use mortar instead of construction adhesive, allow the rocks to remain damp and skip ahead to the last step in this section.
For the best results, choose a construction adhesive that is specifically designed for masonry applications.
Check the product instructions for recommended drying times.
While both stones are still damp, stir together the mortar mix and water according to the package instructions until you’ve created a medium-thick paste. Use a trowel to apply a roughly 1 in (25 mm) bed of mortar to one of the stones. Nestle the other stone into the mortar, wiggling it slightly, and support the stones with wire, rope, or tape while the mortar cures. Consult the mortar mix package for curing times.
You can skip this step if the rocks already have a rough surface.
If you choose to use soapy water, rinse the rocks thoroughly to get rid of soap residue.
Epoxy Resin: Mix the two liquid components in a disposable container with a wooden stirring stick, then apply it right away to one of the stones. Hold the stones together for at least 30 seconds while the epoxy resin cures. Epoxy Putty: Knead the two components together by hand until the separate colors have been thoroughly combined into a new color. Press a medium-thick layer of putty onto one of the stones, then press the other stone in place for at least 30 seconds. [7] X Research source
For the best results, pick out a super glue that’s specifically designed for exterior use. Wear disposable gloves to keep the glue off of your skin.
Check the product instructions for specific drying and curing times.
Bonding agents work best on pea gravel beds that are approximately 1 in (25 mm) deep, but they can be applied to deeper beds as well. If you’re pouring new pea gravel, lay down landscaping fabric first.
Depending on the thickness of the bonding liquid, you may have to drill bigger holes into your watering can’s spout. Refer to the product instructions.
Pros: Construction adhesive is affordable and easy to use. Also, since it retains some elasticity after curing, it can stand up to some twisting or shifting of the rocks. Cons: The adhesive usually remains visible between the rocks. Also, even construction adhesives that are designed for exterior masonry and stone tend to degrade over time due to moisture and other extreme conditions.
Pros: Epoxy resin creates a strong hold quickly and stands up well to temperature extremes. It’s also mostly translucent once it fully cures. Cons: As a semi-thick liquid, it can be messy to apply. Because it’s very hard and rigid once it cures, it’s also susceptible to snapping apart despite its adhesion strength.
Pros: Because it’s thick and pliable when first mixed, it’s great for sticking together rocks that aren’t smooth and flat. It also hardens and cures quickly and is very resistant to heat and cold. Cons: Since it becomes so rock-hard and inflexible once it cures, epoxy putty may not stand up well to freeze-thaw cycles or other outdoor conditions that cause the rocks to shift or twist.
Pros: It’s fairly inexpensive, works quickly, and is practically invisible once it dries. Cons: It may not stand up as well to outdoor conditions as compared to epoxy, construction adhesive, or mortar. Also, it only works well if you’re gluing a flat rock surface to another flat rock surface.
Pros: Masonry mortar is inexpensive and easy to mix and apply. It usually stands up well to outdoor conditions. Cons: Mortar can take several days to fully cure, so it’s a longer process than other adhesives. It’s also very noticeable between the rocks, which may or may not be the look you’re going for.
