Last Updated on October 20, 2026 by Umar Farooq
Sandstone vs slate is mostly a question about water. Slate is a dense, layered metamorphic rock that absorbs very little, so it is the safer stone where winters freeze and the surface stays wet. Sandstone is a sedimentary rock made of cemented grains and is more porous, so it needs sealing and good drainage, but it is warmer in color and usually cheaper. The catch is that both words cover a huge range of quality.
I read three comparisons by stone sellers and installers (Petros Stone, Unique Design and Reems Creek) and they agree on the big picture and disagree on cost and sealing. Our own guides to sandstone pavers and slate pavers go deep on each stone. This one is the head-to-head, and I will point out where the rules of thumb break.
Side by side
Here is what the three sources say, put in one table:
| Slate | Sandstone | |
|---|---|---|
| Porosity | Very low, dense | Moderate to high |
| Frost | Handles freeze-thaw best, though poor grades can flake | More vulnerable to spalling and cracking |
| Heat | Dark tones get hot in strong sun | Lighter shades stay comparatively cooler |
| Grip | Cleft face grips; polished is slippery | Somewhat slip-resistant from its texture |
| Sealing | Occasional, penetrating sealer | More often, and a better sealer |
| Cost (stone) | Priciest of the two | Moderate |
| Look | Sleek, wider color range, charcoal to copper | Warm, earthy buffs, golds and reds |
Treat the table as the average. The rest of this article is about the exceptions.
Water is the whole argument
Reems Creek Outdoor Solutions puts slate's water absorption at typically under one percent, which leaves little water in the stone to freeze and expand. Petros Stone calls slate "very impervious" and sandstone like a sponge. That is a fair summary of the average, and the chart shows why it is only an average.
Our sandstone guide covers ASTM C616, which sorts quartz-based stone into three classes: Class I sandstone may absorb up to 8 percent of its weight in water, Class II quartzitic sandstone 3 percent or less, and Class III quartzite 1 percent or less. For comparison, ASTM C936 concrete pavers average 5 percent at most. So a dense Class II sandstone can be tighter than a concrete paver, and a quartzitic one gets close to slate. The slate number in the chart is a retailer's statement, not a standard, so it is an indicator and not a guarantee.
My strong opinion: stop asking "sandstone or slate" and ask for the absorption number. A stone that absorbs 8 percent will behave like sandstone and a stone that absorbs under 1 percent will behave like slate, whatever the pallet is called.
Winter: spalling versus delamination
Both stones fail in cold climates, in different ways.
- Sandstone can spall, where the surface peels off in thin sheets as water freezes in the pores. Reems Creek says sandstone and limestone are more vulnerable to freeze-thaw damage than slate and quartzite.
- Slate can delaminate. Unique Design says slate may flake over time (spalling), and our slate guide explains that poor slate has layers that open when water gets between them. Lighter-colored slates are the ones the guides single out.
So "slate is frost-proof" is not true. Good slate is frost-tough, and poor slate is not. The only test that settles it is a soaked sample: soak a spare piece, freeze it a few nights, and look at the edges.
Heat, grip and pool chemicals
Slate is usually darker, and Unique Design notes it can get warm underfoot in strong sun. Lighter sandstone shades stay cooler. Pick the lighter tone of either stone for a barefoot area and add shade if you can. Our pavers that don't get hot guide has more.
For grip, a natural cleft finish is the answer on both stones, and a polished or honed face is the problem. Petros notes slate is slippery when polished. Algae makes any stone slick in shade.
One more thing: slate changes color when wet. Many slates look much darker after rain and lighten as they dry (our slate guide covers this). That is the stone, not a defect, so judge a sample dry and wet before you choose a shade, and look at it again in the late afternoon sun.
Around a pool, Unique Design says slate holds up well to pool chemicals while sandstone can stain from them. That fits sandstone's porosity, and it fits our travertine advice: seal the stone and rinse the deck.
Sealing: the schedules disagree
The sources do not agree on how often to seal, which is useful to know:
- Reems Creek says softer flagstone typically needs sealing every one to three years, with annual sealing before winter for sandstone and limestone in the mountains, and slate less often.
- Unique Design's FAQ suggests resealing every 2 to 5 years, and says slate needs occasional resealing with a penetrating sealer while sandstone needs a higher-quality sealer that protects against water and UV.
- Petros says slate usually does not need sealing, and sandstone needs it, ideally regularly.
Take the pattern, not the numbers: sandstone needs it first and most, slate later or never. My rule is the one the site uses everywhere: reseal when water stops beading, not when the calendar says so. Use a breathable, penetrating sealer made for natural stone, and test a spare piece because sealers can darken both stones.
What each costs, and why the figures conflict
Slate usually costs more. Unique Design puts slate at $10 to $30 per square foot and sandstone at $10 to $20. A separate article I opened, on bluestone, slate and granite, puts slate at $10 to $30 per square foot for the stone and $15 to $40 installed. Reems Creek says sandstone and limestone give the biggest upfront savings, while slate requires more skilled labor.
Those are four sellers' ranges, and they overlap. My arithmetic: on a 200 square foot patio, a $10 gap in the per-square-foot stone price is $2,000, which is the difference worth shopping for. Reems Creek also warns that lower upfront cost can be offset by higher maintenance cost in wet, exposed spots. That is the real trade: sandstone costs less to buy and more to look after.
Laying them: the base is the same, the thickness is not
Under both stones the base rules do not change. ICPI Tech Spec 2 calls for at least 4 inches of compacted base under a patio on well-drained soil and 2 to 4 more on wet or freezing ground, with a nominal 1 inch of loose bedding sand. The paver base guide covers it.
What differs is the stone. Calibrated sandstone has a uniform thickness and lays fast, while cleft slate varies in thickness across a single piece and needs more bedding. Thin slate tile is not a paver at all, and thin sandstone slabs crack on a driveway. Whichever you choose, read the thickness and the supplier's laying recommendation before you pay.
Cutting, color and what time does to each
Reems Creek says sandstone is easier to cut, and that slate demands more skilled labor. That fits the stones: sandstone is softer, and slate splits along its layers and can chip at a cut edge. Cut either one wet. OSHA's rule for a handheld saw cutting masonry is water on the blade, every time (29 CFR 1926.1153), because both stones make respirable silica dust. Our diamond blade for pavers guide covers blade choice.
Color changes with age as well. Reems Creek says slate tends to hold its color better under UV. Our sandstone guide notes that some sandstones, such as pale grey Kandla Grey, are often described as softening in tone over a few years. That is normal, but it matters if you plan to add a section to the patio later and expect a match. Buy a little extra from the same lot at the start.
Which one for which job
- Freezing winters, wet or shaded patio: dense slate from a known quarry, or a Class II or better sandstone with test data.
- Warm climate, dry patio, tighter budget: sandstone in a light tone, sealed, with good drainage.
- Pool surround: a cleft face of either stone, light in color, rinsed regularly. Slate copes better with the chemicals.
- Driveway: neither as a thin slab. Sandstone setts or cobbles can work on a vehicle-grade base, as our sandstone guide explains.
- Small, high-impact area such as an entry: slate is the more expensive stone, and it is where the cost is easiest to absorb.
Choose by the absorption number, then by the color
If winters freeze and the area stays wet, buy dense slate or Class II sandstone or better, with a test sheet. If budget and a warm look matter and the patio drains well, sandstone is a fair choice, as long as you seal it and keep water moving off it. Do not let a stone's name stand in for its test data. The stone has waited a few hundred million years. It can wait while you ask for a spec sheet.
FAQ
Is sandstone or slate better for a patio?
Slate is generally better for wet or freezing sites because it absorbs less water. Sandstone suits a warmer look and a smaller budget if it is sealed and the patio drains well. Quality varies, so compare each product's absorption figure.
Is slate more expensive than sandstone?
Usually. One source puts slate at $10 to $30 per square foot and sandstone at $10 to $20. Ranges overlap, and labor for slate can add to the difference.
Which gets hotter in the sun, slate or sandstone?
Dark slate can get warm underfoot, while lighter sandstone shades stay cooler. Choose a lighter tone of either stone and add shade for barefoot areas.
Do slate and sandstone need to be sealed?
Sandstone benefits from sealing more often because it is porous. Slate needs it less often, and some sources say it usually does not. Use a breathable stone sealer and reseal when water stops beading.
Which is better around a pool, slate or sandstone?
Slate holds up well to pool chemicals, and sandstone can stain from them. Either needs a cleft or textured face for grip, and lighter tones for comfort.
