A mortar bed is a packed layer, bonded or floating
Thick-bed, mortar-bed, and thick-set installations are the same traditional method. A mortar layer is packed over the surface. Tile is stuck to that layer while the bed is just beginning to dry, or after the bed has cured. Wire may reinforce the bed. The bed either sits on a cleavage membrane and floats, or it bonds to the substrate. On walls, metal lath is anchored and the mortar locks into it.
Strength is argued
Beds began as a leveling and load-spreading layer over a subfloor that already met L/360. Compressive strength could be low, under 1,000 pounds, with sandy mixes that packed quickly. Richer mixes from later manufacturers need more liquid to reach their strength and are sometimes used over insulation. They also take longer to cure and can curl as they dry unevenly. The FAQ says the trade still disagrees about whether that extra strength helps on a slab on grade or on a suspended slab.
Name the assembly
Calling a floor thick-set does not say whether the bed is bonded or floating. Those two details move differently when the substrate cracks.
Source
Fetched 2026-10-11 from Tile Council mortar bed FAQ. The sentences above follow that page. They are not a contractor promise.
Related notes
- Tile notes index
- A cleavage membrane lets the mortar bed slip
- Movement joints relieve stress between tile and its substrate
- Photo gallery
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