Bathroom tiles meet at different kinds of joints. Some are the narrow spaces between neighbouring tiles; others appear where a tiled wall meets a floor, tub, shower tray or fitting. Using the same filler everywhere can cause cracking, gaps or messy repairs.
Quick answer: Grout is generally used to fill tile-to-tile joints across a tiled surface. Flexible silicone sealant is commonly used at movement and connection joints, such as a change from wall to floor or around a bath or basin, when the selected tile system specifies it. The exact product and joint detail matter; neither grout nor surface silicone replaces the waterproofing layer behind the tiles.
What is the difference between grout and silicone?
Grout fills the joints between installed tiles and helps create a finished, cleanable surface. Products vary: cement-based, epoxy and other grout types have different mixing, curing and maintenance requirements. Choose a grout rated for the tile type, joint width and location. Follow the manufacturer’s product sheet for preparation and cleaning.
Silicone is an elastomeric sealant designed to form a flexible joint between surfaces. Sanitary silicone products are commonly used where a joint needs to accommodate movement or connect dissimilar surfaces, for example around a bath, shower tray, basin or tile edge. Product chemistry and compatibility vary, so read the technical data for the exact material and finish.
Sika describes its sanitary sealant products for use around baths, shower trays and sanitary fittings, while its grout products are specified for tile joints. That illustrates the different roles; check the instructions for the brands and installation system on your project. See Sika’s bathroom installation product guidance.
Grout vs silicone: at a glance
| Location or need | Typical product to consider | What to confirm |
|---|---|---|
| Between adjacent tiles on a flat surface | Tile grout | Joint width, tile type, wet-area suitability and cleaning instructions. |
| Where wall meets floor or another plane | Often a flexible sealant, subject to the selected system | Movement expectations and the tile or waterproofing system’s detail. |
| Around a bath, shower tray or basin | Sanitary silicone may be specified | Substrate compatibility, surface preparation, joint size and curing time. |
| Behind tiles in a shower or wet room | A designed waterproofing system | Membrane, corners, penetrations and drain connection; surface caulk alone is not the waterproofing layer. |
Where does grout belong?
Grout is normally used in the tile field, the network of joints between neighbouring tiles. A grout joint has a defined width and depth, and the selected product needs to match them. Very narrow, wide or uneven joints may need a particular grout type. Check the product’s specified joint range instead of filling a gap with whatever material is nearby.
Grout can be easier to colour-coordinate across a large tiled area, but it is not automatically waterproof or maintenance-free. Some products are more stain resistant or less absorbent than others, but their actual performance depends on formulation and installation. Do not assume that a coloured grout line seals the wall against water.
When grout cracks or crumbles, the cause may be movement, poor mixing, incomplete filling, an unsuitable product or a problem beneath the tile. Simply adding a new layer over a failing joint may not solve it. Remove damaged material as directed and assess whether the tile is loose or the substrate has moved.
Where does silicone belong?
Silicone is often specified where surfaces meet at an angle or where small movement is expected, such as a wall-to-floor change of plane, the edge around a bath, or a joint between tile and a basin. A flexible sealant can accommodate movement better than a rigid filler when the joint and product are designed for that purpose.
Use sanitary-grade silicone only where the product is compatible with both adjoining surfaces. Some sealants are unsuitable for particular stones, metals, plastics or coatings. Colour, curing type, ventilation needs and cure time also vary. If a fixture is not stable or a gap is beyond the product’s allowable joint size, silicone is not a substitute for correcting the installation.
Silicone is not a universal fix for a leaking shower. Water can travel behind tile through a failed membrane, drain connection, pipe penetration or loose fitting. If moisture is recurring, investigate the source rather than repeatedly covering the visible joint. The bathroom floor drain guide explains why drain position and surrounding tile slopes need to work together.
How to decide which one to use
1. Identify the joint, not just the room
Ask what the two sides of the gap are: tile and tile, wall and floor, tile and bath, or tile around a pipe. A wet-room location alone does not determine the filler. The joint’s movement and the surrounding system are the key questions.
2. Check the tile and sealant system instructions
Read the grout and sealant technical sheets. Check permitted joint widths, compatible surfaces, primer requirements, application temperature, cure time and cleaning method. If the tile maker, waterproofing manufacturer or installer has a project detail, follow that coordinated detail rather than combining products on guesswork.
3. Prepare the joint correctly
For regrouting, remove loose grout to the depth the product requires without chipping tile edges. For new silicone, old silicone residue usually must be removed, and the surfaces must be clean and dry. Sika’s guidance for replacing a sanitary joint likewise calls for removing existing sealant and preparing the joint before applying new material. See Sika’s bathroom joint sealing instructions.
4. Apply the correct product and allow it to cure
Use the product’s recommended backing material, joint depth, tooling method and cure time. Keep the joint dry for the period stated in the instructions. Do not expose fresh sealant to a shower before it has cured, and do not wash uncured grout prematurely.
Common mistakes to avoid
- Using grout at every wall-to-floor or fixture connection without checking the system detail.
- Using silicone to fill the regular joints across a tile wall or floor.
- Believing surface silicone replaces the waterproofing membrane beneath tile.
- Applying fresh silicone over old residue, soap film or damp surfaces.
- Using a sealant that is incompatible with natural stone, metal, acrylic or another surface.
- Covering a cracked joint without checking for loose tile, movement or a leak behind the finish.
Fixture connections can also be a source of leaks. If a tap is dripping, the cause may be a cartridge, washer, connection or pressure issue rather than the tile joint; see our guide to why a bathroom tap drips. For planning fittings around a basin and shower, review how to choose bathroom taps.
Which should you choose?
Use grout for the tile-to-tile joints specified by the tiling system. Use a compatible flexible sealant, often sanitary silicone, at movement or connection joints where the project detail calls for it. For a shower or wet room, confirm that a complete waterproofing system sits behind the tile and that corners, penetrations and the drain are treated correctly.
If a joint has failed repeatedly, ask a tiler or bathroom installer to diagnose the movement or water path before applying another product. A well-prepared joint with the correct material lasts longer than a quick patch over the wrong detail.
Frequently asked questions
Should I use grout or silicone where a wall meets a shower floor?
A flexible sealant is often specified at changes of plane, but the tile and waterproofing system instructions determine the correct detail. Ask the installer to confirm the product.
Can I put silicone over grout?
Only when the system and product instructions allow it. The grout or tile surface must be clean, dry and compatible; sealant over a failing joint may not solve the cause.
Does silicone make a shower waterproof?
No. Silicone seals specific surface joints. A shower needs a properly designed waterproofing layer and sealed penetrations behind or beneath the tile.
Can I use bathroom silicone between every tile?
Usually grout is designed for regular tile-to-tile joints. Silicone is commonly reserved for selected movement or connection joints. Follow the product and installation details.
How do I know if old silicone needs replacing?
Gaps, peeling, loss of adhesion or persistent mould staining can indicate that the joint needs attention. Check for leaks or movement first, then remove and replace it according to the manufacturer’s instructions.