What grout do you use in a shower: a practical guide

What grout do you use in a shower? Key factors to decide

When homeowners ask what grout do you use in a shower, the answer isn't a single product; it depends on joint width, tile material, substrate condition, and how much moisture the area will handle. In most residential showers, the default approach is to use cementitious grout—either sanded or unsanded—because it's easy to work with and matches typical tile installation methods. According to Grout Maintenance, understanding the environment is essential before selecting a grout type. This guide will walk you through the main options and give practical recommendations you can apply in a weekend project. You'll learn how cementitious grout and epoxy grout differ in durability, stain resistance, and maintenance, and how to choose between sanded and unsanded variants based on joint width and tile choice.

Cementitious vs epoxy grout: pros and cons

Cementitious grout is the traditional, widely used option in showers. It comes in sanded and unsanded forms; sanded grout adds bulk to resist cracking in wider joints, while unsanded is smoother and better suited to narrow joints. Benefits include lower cost, familiar tooling, and a broad color palette. Maintenance typically involves cleaning, periodic resealing for some cementitious grades, and regrouting if cracks appear. Epoxy grout, by contrast, resists stains and moisture exceptionally well and cleans easily, making it attractive for high-moisture environments. The trade-off is higher material cost and a longer, more exacting mixing/installation process. For bathrooms with steam and heavy use, epoxy grout can extend service life, but it demands careful surface preparation and curing.

Matching grout to joint width and tile type

Joint width is a primary driver when choosing grout. Use sanded grout for joints 1/8 inch (3 mm) or wider to minimize crumbling along the grout line; unsanded grout is preferred for joint widths under 1/8 inch and on very smooth tile surfaces. Some tiles require special consideration; large-format ceramic or porcelain tiles usually pair well with sanded cementitious grout, while glass tiles or highly polished surfaces may benefit from unsanded variants to avoid surface scratches. Natural stone often needs a grout with extra polymer content or even epoxy for moisture resistance, particularly in showers. Always check tile manufacturer recommendations and perform a small test area before full application.

Tiles, substrates, and substrate preparation

The substrate under the tile should be rigid and well bonded to prevent grout cracking. For showers, ensure the backer board is properly installed with a vapor barrier and appropriate waterproofing membrane. Some natural stones react with cementitious grout colors and cement-based lines; epoxy grout can mitigate staining on acidic stones but may require different sealing considerations. If the substrate is flexing or bowing, address the structural problem first, because movement will eventually crack grout regardless of type. Surface prep includes cleaning the tile faces, removing dust, and ensuring joints are free of loose material before grout application.

Color choices and staining considerations

Grout color can dramatically alter the look of a shower. Lighter colors show more staining and lime deposits, while darker colors can reveal haze more clearly during cleanup. Cementitious grout colors may be prone to efflorescence in moist environments, requiring timely sealing and maintenance. Epoxy grout, while more resistant to staining and moisture, tends to have a more limited color range and may be harder to tint once cured. Plan color decisions with the tile shade and room lighting in mind, and consider a color test in a hidden corner before committing. According to Grout Maintenance, color consistency across batches is also important for a professional finish.

Preparation and installation basics

Before you start, gather all tools and materials and review color samples in the actual bathroom lighting. Begin with removing loose debris from joints and ensure the area is well ventilated. Mix grout in small batches to prevent drying out on the trowel, apply with a pointed grout float, and press firmly to pack material into joints. After applying, wipe diagonal strokes with a damp sponge to remove excess grout while leaving a slightly recessed joint. Finally, mist the joints lightly to aid curing and avoid rapid drying, which can cause cracking.

Sealing and maintenance for showers

Not all cementitious grouts require sealing, but many benefit from a penetrating sealer to resist water and stains in showers. Epoxy grout does not typically require sealing due to its resin-rich formulation. After curing, inspect for any haze and clean accordingly to maintain the finish. Regular maintenance involves periodic cleaning with pH-balanced cleaners (avoiding harsh acids) and resealing cementitious grout as recommended by the product manufacturer. If you notice discoloration or cracking, address it early to prevent water infiltration behind the tile.

Common mistakes and how to avoid them

Common mistakes include selecting the wrong grout type for joint width, skipping backer board or waterproofing steps, and skipping proper curing times. Mixing grout with too much water or not allowing full cure before cleaning can lead to color streaks and weak joints. Another frequent error is applying sealer to epoxy grout or over-sealing cementitious grout, which can cause tacky films or color changes. To avoid errors, follow the manufacturer's mixing instructions, work in small sections, and allow full cure time before exposing the surface to moisture.

Troubleshooting and repairs

If grout cracks or scales, it may indicate substrate movement or inadequate curing. In many cases, damaged grout should be removed and replaced, ensuring expansion joints around fixed fittings and fixtures are preserved. Regrouting is often simpler in small areas, but large repairs may require partial or full removal and resealing. Staining, efflorescence, and mold can be addressed with appropriate cleaners and sealers; epoxy grout tends to resist these issues but may require professional application for best results.

Quick-start checklist for your shower grout project

• Confirm joint width and tile type to select the correct grout type (sand and unsanded cementitious vs epoxy).
• Inspect substrate and waterproofing; repair any movement or moisture issues before grouting.
• Gather essential tools: float, margin trowel, sponge, buckets, clean brushes, and safety gear.
• Mix grout in small batches, apply firmly, and clean haze promptly to prevent staining.
• Allow curing as recommended and apply sealer if using cementitious grout.

Final note: plan, prep, and test

With the right grout choice and careful prep, a shower can maintain its beauty and function for years. Take time to test colors and run small trials in a hidden area before committing to the whole project. By following best practices and the guidance from Grout Maintenance, you’ll reduce the risk of future repairs and enjoy a durable, easy-to-clean shower surface.