How To Glue Sandstone to Sandstone
What is the best adhesive for gluing sandstone to sandstone outdoors?
Check the Liquid Nails Landscape specification
Selleys' product page and its dated technical sheet disagree on Landscape's chemistry, colour, paintability and pack size. Landscape figures below from the November 2020 technical sheet describe that document, not a confirmed specification for every current cartridge. Confirm the matching instructions before painting, choosing a colour, or relying on cure and loading times. See the source comparison and dated documents.
Liquid Nails Landscape is the product for this. It is made for landscape work — stabilising stone, bonding pavers to concrete and similar jobs — so gluing sandstone to sandstone falls squarely inside what it is designed for. The one limit to note up front: it is not for permanent water immersion. An outdoor wall or step that gets rained on is fine; a pond wall, a water feature or anything sitting permanently in water is not.
What it is and what the figures mean
Liquid Nails Landscape is a premium grade, high strength construction adhesive based on neutral cure silicone. It delivers a weather resistant, high strength, flexible and shock proof bond. For Landscape, confirm the specification for your cartridge: the manufacturer sources disagree.
| Property | Typical result |
|---|---|
| Technology | Neutral cure silicone |
| Colour | Grey |
| Specific gravity @ 25 °C | ~1.35 |
| Skin time | 10–15 minutes |
| Cure rate | 2 mm / 24 hrs |
| Tack free time | 35 ± 5 minutes |
| Slump | < 0.1 inch |
| Shore A hardness | ~30 |
| Elongation at break | >300% |
| Packaging | 300 g cartridge |
Indicative data only, not intended for the preparation of specifications.
The elongation at break of over 300% and Shore A hardness of about 30 are what make this a sensible choice for stone outdoors. It is not a rigid glue. Sandstone blocks in the sun expand and contract, and a brittle bond line would crack; a flexible one absorbs that movement. It is also why the TDS describes the bond as shock proof.
The 5-minute assembly window is the tight part. You must bring the surfaces together before the product skins, and skin time is 10–15 minutes. Stone is heavy and awkward, so have the blocks staged, cleaned and dry-fitted before you cut the cartridge.
The 2 mm per 24 hours cure rate is worth understanding for a stone joint. Adhesive squeezed to a thin film between two dressed faces cures quickly; a thick bed filling an uneven joint takes days. Neutral cure silicone also needs atmospheric moisture to cure, and a thick bond sandwiched between two dense faces has limited access to it.
Sandstone's own limitation
The TDS says not for soft or crumbly materials, and this is the one to check on your particular stone. Weathered sandstone can be friable — if you can rub grains off the face with a thumb, the adhesive will bond perfectly well to a surface that is itself about to let go. Brush the faces back to sound stone, and if the surface still crumbles, adhesive is not the right fixing method.
Sandstone is also porous and holds water for a long time after rain. The TDS calls for the surface to be sound, dry and free from oil, grease and loose powdery material. Give the stone genuine drying time rather than assuming a dry-looking face is dry.
How to do it
- Clean both faces. Remove moss, dirt and loose material. If necessary, clean with mineral turpentine and allow to dry.
- Dry-fit the blocks and work out the sequence before any adhesive comes out.
- Cut the cartridge tip, fit the nozzle and cut it to a suitable opening — approximately 5 mm — and load it into a caulking gun.
- Apply dobs or beads of an appropriate thickness to ensure sufficient contact and spread between both surfaces. Keep the adhesive at least 12 mm in from the edges to minimise squeeze-out.
- Bring the surfaces together within 5 minutes, before the product skins, and apply enough pressure to spread the adhesive between both faces.
- Do not wipe excess squeeze-out. Wait until the product cures, then trim it with a sharp blade, avoiding cutting into the bond. Wiping smears grey silicone into porous sandstone, where it is very hard to remove.
- Leave the job undisturbed until the adhesive has cured sufficiently. Do not allow traffic on stairs or use walls for at least 24 hours.
Limitations
- Not for permanent water immersion.
- Cannot be painted over.
- Not for soft or crumbly materials.
- Do not use as the sole bonding agent for structural bonding. A retaining wall or anything load-bearing needs proper construction, with the adhesive as a stabiliser rather than the structure.
- If repositioning materials, fresh adhesive must be applied to achieve bonding. You cannot lift a block, adjust it and put it back down on the same adhesive.
- The product releases methyl ethyl ketoxime during cure. Keep out of reach of children, avoid skin and eye contact and breathing vapours, and cure the product before disposal.
Common questions about gluing sandstone
Can I use it around a pond or water feature?
No. Liquid Nails Landscape is not for permanent water immersion. Splash and rain are fine; standing water is not.
How long before I can walk on stone steps I have glued?
Do not allow traffic on stairs or use walls for at least 24 hours, and remember the adhesive continues curing at 2 mm per 24 hours through its thickness.
My sandstone is a bit soft — will it still work?
The TDS says not for soft or crumbly materials. Brush the faces back to sound stone first. If they still crumble, the bond will only be as strong as the surface it is stuck to.
Can I paint or render over the joint?
No, it cannot be painted over. The adhesive is grey, so it reads reasonably well against most sandstone if you keep squeeze-out under control.
What if I get adhesive on the stone face?
Leave spilt or smeared adhesive to cure and then remove it by abrasion — that is the TDS's own recommendation. Uncured product can be removed with mineral turpentine, and cured product with the help of Selleys Sealant Remover or by mechanical action, but on porous sandstone, wiping while wet drives it into the surface.
Is one cartridge enough?
Liquid Nails Landscape comes in a 300 g cartridge. Coverage depends entirely on how much you need to fill an uneven stone joint, so buy more than you think for a wall of any size. For Landscape, confirm the specification for your cartridge: the manufacturer sources disagree.
What if I am bonding stone to a concrete slab instead?
That is a listed use — bonding pavers to concrete. See also fixing a cement paver to a concrete surface and bonding brass to sandstone.
Is there a more flexible, paintable alternative for outdoor stonework?
Selleys 650 FC is a hybrid adhesive sealant with ±20% joint movement, greater than 500% elongation at break and it can be painted once cured. It has excellent adhesion to concrete, masonry and brick — though like Liquid Nails Landscape it is not recommended for continuous submersion. For Landscape, confirm the specification for your cartridge: the manufacturer sources disagree.
What is the best adhesive for gluing sandstone to sandstone in an outdoor setting?
Selleys® Liquid Nails® Flex is recommended for gluing sandstone to sandstone. It is a flexible construction adhesive specifically engineered to bond effectively to sandstone as a non-porous substrate, making it ideal for sandstone-to-sandstone applications, including outdoor settings.
How should sandstone surfaces be prepared before gluing?
Sandstone surfaces should be thoroughly cleaned to remove dirt, dust, oil, grease, and loose particles using mineral turpentine or turps-based solutions, then allowed to dry completely. The bond areas should also be lightly sanded or abraded to enhance mechanical adhesion, and any old adhesive, sealant, or caulk should be removed if re-bonding.
What is the process for applying Selleys® Liquid Nails® Flex to sandstone?
First cut the cartridge tip and fit the nozzle, then load the cartridge into a caulking gun. Apply the adhesive in a continuous bead or beads (approximately every 40 centimetres on broad flat surfaces), press the sandstone pieces firmly together to ensure good contact, and allow adequate curing time before subjecting the bond to stress.
How long does it take for Selleys® Liquid Nails® Flex to fully cure on sandstone?
Full cure typically takes 7 days before the bond should be subjected to stress.
Why is Selleys® Liquid Nails® Flex suitable for bonding sandstone?
It offers flexibility and strong, long-lasting bonds on both porous and non-porous surfaces like sandstone, along with excellent moisture-curing properties suitable for demanding applications.
Which brand produces the Ask an Expert guidance on gluing sandstone to sandstone?
Selleys, an Australian adhesives, sealants and fillers brand founded by Martin Selley in 1939 in Sydney, Australia, and a division of DuluxGroup (Australia) Pty Ltd, provides this guidance.