What is Grout?
Grout is a cement-based or epoxy-based material used to fill the joints between tiles after installation. It serves multiple purposes: it prevents moisture from seeping beneath tiles, locks tiles in place, provides structural support, and creates a finished appearance. The choice of grout type and color significantly impacts both the durability and aesthetics of the tiled surface.
Calculating the correct amount of grout prevents waste and ensures you have enough material to complete your project without interruption. Running out mid-project can lead to color variations between batches, so it is best to purchase all needed grout from the same production lot.
Grout Calculation Formula
Grout density is approximately 100 lb per cubic foot for sanded grout.
Grout Types
| Type | Joint Width | Best For | Coverage (25-lb bag) |
|---|---|---|---|
| Unsanded | 1/16" to 1/8" | Wall tiles, polished stone | 80 – 120 sq ft |
| Sanded | 1/8" to 1/2" | Floor tiles, wide joints | 50 – 90 sq ft |
| Epoxy | 1/16" to 1/2" | Wet areas, commercial | 60 – 80 sq ft |
| Furan | 1/4" to 1/2" | Chemical resistance | 40 – 60 sq ft |
Joint Width Guidelines
- 1/16": Rectified tiles with very precise edges. Requires unsanded grout.
- 1/8": Most common for wall tiles and precision floor tiles.
- 3/16": Standard for most floor tiles. Good balance of appearance and forgiveness.
- 1/4" to 3/8": Handmade tiles, natural stone, and rustic installations.
- 1/2"+: Large-format pavers and specialty installations.
Worked Example
100 sq ft of 12"x12" tiles with 1/8" joints and 3/8" thick tiles:
Frequently Asked Questions
How much grout do I need per square foot?
It varies widely based on tile size, joint width, and tile thickness. Small mosaic tiles with wide joints can use 10x more grout per square foot than large format tiles with narrow joints. Use the calculator above for accurate estimates.
What is the difference between sanded and unsanded grout?
Sanded grout contains fine sand particles that provide strength in wider joints (over 1/8"). Unsanded grout is smooth and used for narrow joints under 1/8" and on polished stone where sand could scratch the surface.
How long does grout take to cure?
Grout is typically firm enough to walk on after 24 hours and reaches full cure in 28 days. Avoid heavy traffic and moisture exposure for the first 72 hours. Apply grout sealer after full cure for maximum protection.
Should I seal my grout?
Yes, cement-based grout should be sealed to prevent staining and moisture absorption. Apply a penetrating sealer after the grout has fully cured (28 days) and reapply every 1-2 years. Epoxy grout does not require sealing.