DIY dry-pack mix at 5:1 — buy sand + portland cement:
Tip: add about 10% extra for screeding and packing waste.
Tiling over the mud bed? Estimate your tile too.
Shower Tile Calculator →Mud Bed Supplies
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What Is Deck Mud?
Deck mud — also called floor mud, dry pack, or a mortar bed — is a stiff, sandy mix of sand and portland cement with just enough water to hold together when squeezed. It's used to build the sloped base under shower floors and to level subfloors before tiling. Because it contains no lime and very little water, it packs hard and won't slump on a slope.
Standard Deck Mud Formula
The classic deck mud ratio is 5 parts sand to 1 part portland cement by volume. A 4:1 mix is a bit richer and stronger; 6:1 is leaner and more economical for thicker fills.
How Much Sand and Cement?
In a dry-pack mix the cement and water fill the gaps between sand grains, so the finished bed volume is roughly equal to the loose sand volume. The calculator above sizes the sand to your bed volume and the portland cement to your chosen ratio.
Frequently Asked Questions
How do I calculate deck mud by the square foot?
Multiply the floor area in square feet by the average bed thickness in inches, then divide by 12 to get cubic feet. For example, a 3 × 3 ft shower pan (9 sq ft) at an average 1.5" thickness needs about 1.1 cubic feet of deck mud. Enter your numbers above for an exact sand and cement count.
Is deck mud the same as floor mud?
Yes. "Deck mud" and "floor mud" both refer to the same dry-pack mortar — sand and portland cement at roughly 5:1. "Wall mud" or "fat mud" is different: it adds lime so it sticks to vertical surfaces.
How thick should a mud bed be?
A shower pan mortar bed should be at least 1.25 inches at the drain and slope up about 1/4 inch per foot toward the walls, so the average thickness is usually 1.5–2 inches. For leveling a subfloor, beds typically run 1/2 inch to 2 inches.
What's the right sand-to-cement ratio for deck mud?
The standard is 5:1 (sand to portland cement). Use 4:1 for a stronger bed under heavy tile, or 6:1 to stretch material on a thick pour. Avoid masonry cement (it contains lime) for floor beds.
Can I use pre-mixed bags instead of sand and cement?
Yes — a sand/topping mix or a bagged "deck mud" / "sand mix" works well and saves measuring. Each 60 lb bag yields roughly 0.5 cubic foot, so divide your bed volume in cubic feet by 0.5 to get the bag count.