Installing Flat Rock Over an Existing Brick Paver Patio

Preparation and Drainage Are Critical

User has leftover flat rock from a fireplace and wants to lay it over brick pavers.

Recommended Build-Up

1. FIN drain (optional but ideal): Geotextile sandwich with hollow core for drainage. Permeable top, impermeable bottom, outlets water.
2. Drill ½-inch holes in pavers for additional drainage.
3. Sand base: 4 inches of concrete sand (not masonry sand).
4. Gravel sub-base: 8 inches if soil is clay/silt, with filter fabric between sand and gravel.

Joint Treatment

• Narrow joints: sweep in sand (masonry sand okay for joints).
• Wide joints: use mortar (mortared design sheds water, no drainage needed below).

Weight Limit

Do not place very heavy rock on pavers. Medium-weight rock is acceptable.

Without FIN Drain

Not recommended—poor drainage leads to freeze/thaw damage.