Deck Mud Coverage Chart: Bags for a Shower Floor

A 50 lb bag of deck mud makes about 0.41 cu ft, which covers about 10 sq ft at ½ in thick, 4.9 sq ft at 1 in and 2.5 sq ft at 2 in. A standard 36 × 60 in shower floor, sloped from ¾ in at a centre drain, takes about 4 bags.

Deck mud coverage chart

Coverage per bag at an even thickness, from the yield on Quikrete's Deck Mud data sheet (0.41 cu ft per 50 lb bag, 0.62 cu ft per 75 lb bag). Other brands differ: TEC lists its 50 lb floor mud at 4.25 sq ft at 1 in, a little less, so check your bag.

Deck mud coverage per bag by thickness
Thickness	50 lb bag	75 lb bag
½ in (12 mm)	9.8 sq ft (0.91 m²)	14.9 sq ft
¾ in (19 mm)	6.6 sq ft (0.61 m²)	9.9 sq ft
1 in (25 mm)	4.9 sq ft (0.46 m²)	7.4 sq ft
1½ in (38 mm)	3.3 sq ft (0.3 m²)	5 sq ft
2 in (50 mm)	2.5 sq ft (0.23 m²)	3.7 sq ft

How many bags of deck mud for a shower floor?

A shower floor isn't flat: it slopes ¼ in per foot down to the drain, so it's thinnest at the drain and thickest at the walls. The table assumes a centre drain, ¾ in of mud at the drain and level walls, and adds 10% for mixing and waste.

Deck mud for a sloped shower floor (centre drain)
Shower size	Floor area	Average thickness	Mud needed	50 lb bags (+10%)
32 × 32 in	7.1 sq ft	0.97 in	0.58 cu ft	2
36 × 36 in	9 sq ft	1 in	0.75 cu ft	3
36 × 48 in	12 sq ft	1.08 in	1.08 cu ft	3
36 × 60 in	15 sq ft	1.17 in	1.46 cu ft	4
42 × 60 in	17.5 sq ft	1.17 in	1.7 cu ft	5
48 × 48 in	16 sq ft	1.08 in	1.44 cu ft	4
60 × 60 in	25 sq ft	1.17 in	2.43 cu ft	7

With a linear drain along one wall, the floor is a single slope and the average thickness is the drain thickness plus half the rise to the far wall. A 36 in deep shower with ¾ in at the drain averages about 1.13 in.

Worked example: a 36 × 60 in shower

Floor area: 36 × 60 ÷ 144 = 15 sq ft.
Rise to the walls: the farthest wall is 30 in (2.5 ft) from the drain, so 2.5 × ¼ = 0.625 in. The mud is ¾ in at the drain and 1.375 in at the walls.
Average thickness: ¾ + ⅔ × 0.625 = 1.17 in. (With four slopes meeting at a centre drain, the average is two-thirds of the way up.)
Volume: 15 × 1.17 ÷ 12 = 1.46 cu ft.
Bags: 1.46 × 1.1 ÷ 0.41 = 3.9, so buy 4 bags of 50 lb.

Bags for a flat mortar bed

For a floor bed of even thickness (no slope), 50 lb bags with 10% extra:

50 lb bags of deck mud for a flat bed
Area	¾ in	1 in	1½ in	2 in
10 sq ft	2	3	4	5
20 sq ft	4	5	7	9
30 sq ft	6	7	11	14
50 sq ft	9	12	17	23
100 sq ft	17	23	34	45

Mixing your own deck mud

Deck mud, also called dry-pack or floor mud, is sand and Portland cement mixed at about 5 parts sand to 1 part cement by volume (some installers use 4 to 1), with just enough water that a squeezed handful holds its shape without water running out. Pre-blended bags save measuring and give a consistent mix; mixing your own is cheaper for large floors.

Common mistakes

Using the thickness at the drain. The bed gets thicker toward the walls, so working from the drain thickness can leave you a bag or two short.
Going below the bag's minimum. Quikrete Deck Mud is rated for ½ to 2 in. Check the minimum for your product and your drain's instructions.
Mixing it too wet. Wet mud slumps and won't hold the slope. It should look damp and pack like sand for a sandcastle.
Forgetting the second layer. A traditional liner shower has a pre-slope under the liner and a mortar bed on top: count the mud for both.

For the tile and grout on top, use the tile and grout calculator.