The slip-resistant, low-maintenance stone with the most natural character.
Slate is a fine-grained metamorphic rock formed from clay, volcanic ash, and fine sediment compressed under pressure. Its defining characteristic is its cleavage — it splits naturally into flat planes, creating the unique cleft surface texture. Slate has been used for roofing and flooring for centuries across Europe and Asia.
By the numbers
| Mohs hardness | 4–5 |
| Water absorption | 0.3% |
| Freeze-thaw | Very good |
| Density | 2.78 g/cm³ |
| Applications | Roofing, flooring, wet rooms |
| Cost range | $6–14 / sq ft |
Surface options
The authentic split surface — rough, textured, irregular. Maximum character and slip resistance.
Natural cleft top with ground-flat back. Consistent thickness, easier installation.
Sanded flat and smooth. Loses the cleft texture — unusual for slate but used in some contemporary applications.
Edges tumbled for a worn, antique look. Used in smaller formats for mosaic and feature walls.
Pros & cons
Advantages
- ✓ Best natural slip resistance of any stone (cleft surface)
- ✓ Low maintenance — many grades need no sealing
- ✓ Great value — mid-price-range natural stone
- ✓ Dramatic visual character — earthy, authentic
- ✓ Excellent for wet rooms: showers, bathrooms, exterior steps
- ✓ 100-200 year roofing lifespan
Considerations
- – Color variation between batches from same quarry
- – Cleft surface collects dust and is harder to sweep
- – Softer than granite — chips from impact with heavy objects
- – Multicolor Chinese slates can delaminate if quality is poor
- – Less popular in luxury residential markets (lower resale signal vs. marble)
Slate — common questions
How to Lay a Natural Slate Floor
Installation guide for natural cleft or gauged slate flooring.
Select gauged vs. ungauged slate
Gauged slate has been ground to a consistent thickness on the back — easier to set because all tiles lay flat. Ungauged (natural cleft) slate varies in thickness and requires more mortar and skill to level. For beginners, gauged slate is strongly recommended. Both have the same natural cleft surface on top.
Prepare the substrate
Install cement board over a solid subfloor. Ensure the floor is flat within 1/8" in 10 feet — slate's rigidity means it will crack if it bridges a dip. Fill any depressions with floor leveling compound before setting.
Lay out the pattern
Slate is typically set in a random or ashlar pattern. Dry-fit a section before committing to mortar — arrange pieces for color balance (dark, medium, light) and size variation. Avoid lining up joints in adjacent rows (stagger by 1/3 the tile length minimum).
Set in thinset
Use grey polymer-modified thinset for slate. Back-butter each piece for full contact. For ungauged slate, vary mortar bed thickness per piece. Level using a rubber mallet and level. Slate can vary 1/4" in thickness across a single piece — account for this with mortar.
Seal and finish
After grout cures (72 hours), apply a penetrating color-enhancing sealer to enhance the slate's depth and enrich natural tones. For exterior slate, use a water-repellent sealer. Slate requires less frequent sealing than marble or travertine — typically every 3–5 years.
Slate price guide
The full Slate price guide covers material vs. installed costs, regional pricing across all 6 US regions and Canada, format-specific breakdowns, and the top cost drivers for your project.
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