Tile bedding
Tile bedding is the mortar or adhesive layer under a tile. When to use thin-bed adhesive vs thick-bed mortar, and how it differs from the screed below.
Ask Chalkline about this →Tile bedding is the mortar or adhesive layer in which a tile is set. It sits between the finished tile and the substrate (or the screed over the substrate). The bedding method drives the bond, the lippage, and whether the floor sits to fall or to level.
Thin-bed vs thick-bed
The two main bedding methods:
- Thin-bed: a notched-trowel layer of tile adhesive (typically 3 to 6 mm bed thickness after the tile is laid). Standard for modern installations over a flat substrate. Faster, lighter, lower cost; requires the substrate or screed to be already flat to tolerance.
- Thick-bed (mud-bed, sand-cement bed): a 20 to 30 mm sand-cement mortar bed laid wet, with the tile bedded into it. Used over out-of-tolerance substrates, where falls have to be built into the bed, and on traditional shower bases. Slower and heavier; tolerates a substrate the thin-bed adhesive cannot.
The choice comes down to substrate condition and the falls required: a thin-bed adhesive cannot correct a 10 mm dip in a slab, but a thick-bed mortar can.
How it differs from neighbours
- Tile bedding is the set layer the tile lives in.
- Screed is the layer below the bedding that brings the substrate to level or sets the fall to a drain.
- Tile adhesive is the product used in thin-bed work, classified under AS ISO 13007.
In a wet-area floor, the order from substrate up is: substrate, screed (with fall), waterproofing membrane, tile bedding, tile.
What goes wrong
- Wrong method for the substrate: thin-bed on a wavy slab transmits the slab’s profile to the tile face, with lippage.
- Insufficient bedding coverage: less than the adhesive coverage the manufacturer and AS 3958 require leads to hollow tiles, cracking, and debonding under impact.
- Skipping back-buttering on large-format: thin-bed without back-butter on a 600 mm+ tile rarely achieves the coverage the system needs (see large-format tile).
Also known as: tile bed, tile-bed method, thin-bed thick-bed.
Category: Finishes / tiling
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Last updated: 2026-05-29. Verified: 2026-05-29. Quarterly review for currency.