Deck mud coverage chart (dry pack mortar)
Quick deck mud coverage table, mixing notes, and practical tips for estimating dry pack mortar by area and thickness.
Quick coverage table
Deck mud (dry pack mortar) is usually estimated by volume: area × average thickness. The table below is a fast planning reference for common thicknesses.
| Coverage | 1 inch thickness | 1.5 inches thickness | 2 inches thickness |
|---|---|---|---|
| 50 sq ft | 4.17 cu ft | 6.25 cu ft | 8.33 cu ft |
| 100 sq ft | 8.33 cu ft | 12.5 cu ft | 16.67 cu ft |
| 150 sq ft | 12.5 cu ft | 18.75 cu ft | 25 cu ft |
Quick volume rule (easy mental math)
A simple rule of thumb: 100 sq ft at 1 inch thickness is about 8.33 cubic feet. Scale that up or down by thickness. For example, 80 sq ft at 1.5 inches is 8.33 × 0.8 × 1.5 ≈ 10 cu ft.
Cubic yards quick reference
1 cubic yard = 27 cubic feet. Convert your total cubic feet to yards by dividing by 27.
Example: 18.75 cu ft / 27 = 0.69 cu yd (round up if ordering bulk).
Thickness conversion (inches to feet)
Thickness in feet = thickness in inches / 12. Use that value for volume: area x thickness (ft).
- 1 inch = 0.083 ft, 1.5 inches = 0.125 ft, 2 inches = 0.167 ft.
Worked example (quick order)
Example: 40 sq ft at 1.25 inches: volume = 40 x (1.25/12) = 4.17 cu ft. Add 10% waste to about 4.6 cu ft.
Bag planning notes
- Use the bag yield on the label (cu ft per bag).
- Bags needed = total cu ft / bag yield, then round up.
- Keep a small buffer for mixing loss and cleanup.
Mix ratio and consistency (dry pack basics)
Deck mud (dry pack) is intentionally low-water and packable. The goal is a stable, shaped bed you can compact and screed flat or to slope.
Ratios vary by application and local practice, but many mixes start around 5:1 sand-to-cement by volume. Follow your waterproofing/system guidance for critical installs.
| Ratio (by volume) | Use note | Reminder |
|---|---|---|
| 5:1 sand:cement | Common starting point | Follow system guidance |
| 4:1 sand:cement | Sometimes for higher strength | Workability changes |
- Use a consistent container for volume ratios and measure water the same way each batch.
- Squeeze test: it should hold together when squeezed, but it should not ooze water.
- Mix thoroughly before adding more water; dry pockets create weak areas.
Slope planning: estimate by average thickness
A sloped bed is thicker at the perimeter than at the drain. Estimate volume using average thickness: measure your high and low points and average them.
- Confirm the waterproofing system and drain type first; they determine build-up.
- Prefer fewer “surprises” mid-bed: estimate total volume, plan batches, and round up to avoid cold joints.
- If you must patch or blend batches, aim for consistent mix feel so finish texture stays uniform.
Practical notes
- Use average thickness. If you are correcting slope, measure high and low points and average them.
- Round up. Running short mid-bed is usually more expensive than a small buffer.
- Mix ratios vary by application and local practice; follow product and manufacturer guidance for critical installs.