Does natural stone veneer
need to be sealed?

No. Natural stone veneer does not require sealing.

This is the most common misconception about the material, and it costs homeowners money every year. The stone sat in Michigan ground through a great many freeze-thaw cycles without a sealer. It does not need one on a wall.

If a sealer is specified anyway

There are legitimate aesthetic reasons — deepening color, or reducing staining on an interior application near a cooktop or a hearth. If a sealer is going on, the type matters far more than the brand.

• Use a breathable, penetrating impregnator rated for exterior natural stone.
• Do not use a film-forming or wet-look topical sealer on exterior work.
• Inspect annually, and expect to reapply on a cycle set by the sealer manufacturer.

Breathable is the operative word. A film-forming sealer traps moisture behind the stone, and in a freeze-thaw climate trapped moisture is the failure mechanism. A sealer applied to make a wall look better can be the thing that spalls it.

Why the stone does not need it

Absorption is what a sealer is meant to address, and these are low-absorption stones. Tested per ASTM C97 by Driesenga & Associates: