Grout and sealant both fill joints in a bathroom, and both can go black, crack or leak. But they are different materials, and they belong in different places. Putting the wrong one in a joint is a common reason bathrooms leak. This guide explains the difference, how to tell which needs work, and why the two are often done together.
The difference in one sentence
Grout is rigid and fills the joints between tiles. Sealant is flexible and fills the joints where two different surfaces meet or where things move.
Tiles on a wall are fixed and move very little against each other, so a rigid grout is fine. But a bath, shower tray or worktop moves slightly against the wall every time it is loaded and unloaded. A rigid material in that joint cracks. A flexible sealant stretches and recovers.
Which joints need which
| Joint | Usually |
|---|---|
| Between wall tiles | Grout |
| Between floor tiles | Grout, with movement joints where needed |
| Bath, tray or basin to wall | Sealant |
| Internal corners of a shower | Sealant |
| Tiled floor to wall or skirting | Sealant |
| Worktop to wall or upstand | Sealant |
Internal corners in showers are a common mistake. They are often grouted, then crack, and water gets in. A flexible sealant is the better choice there.
Signs your grout needs attention
- Cracked or crumbling grout, or gaps between tiles
- Black mould deep in the grout that won’t clean out
- Grout that is soft or washes away when scrubbed
- Tiles that sound hollow or move, which can mean water has got behind them
Our regrouting service covers raking out and replacing old, cracked or stained grout.
Need it done properly? Mr Mastic covers the South East, London and Scotland, with a one-year guarantee on every job. Call or email for a quick quote.
Signs your sealant needs replacing
- Black mould inside the bead
- Gaps where the bead has pulled away from the bath or tile
- Cracks, splits or shrinkage
- A gap that opens when the bath is full
See our guide to cleaning mould from silicone for when cleaning will and won’t help.
Why they are often done together
Grout and sealant meet. The bead along a bath sits against the bottom row of tiles and their grout. If the grout there is cracked, water can get behind the tiles above the sealant. If the grout is being replaced, the sealant is often disturbed anyway.
So when a bathroom has both problems, it usually makes sense to regrout first and reseal after, so the new bead goes onto clean, sound tiles and grout. Doing both in one visit also means the bathroom is only out of use once. We often pair resealing with regrouting for this reason.
Grout colour and finish
Grout comes in many colours, and regrouting is a chance to change the look of a bathroom. A darker grout hides staining better in a busy shower. White grout looks crisp but shows marks more quickly. Grout colourants can also refresh old grout that is sound but stained.
If you change the grout colour, think about the sealant too. A grey grout often looks best with a grey or matched sealant. Matching the two keeps the finish consistent.
Quick answers
Can I grout the gap between the bath and the tiles?
It isn’t recommended. The bath moves, so rigid grout in that joint will crack. Use a flexible sealant.
Can I put sealant over cracked grout?
No. Sealant over grout lines doesn’t bond well and hides the problem. Cracked grout should be raked out and replaced.
Which should be done first?
Regrout first, then reseal, so the new bead goes onto clean, finished tiles.
How long does regrouting take to set?
It depends on the grout. Follow the manufacturer’s instructions, and allow it to set before the sealant goes on.
Related services
More advice
- Sealing a Wet Room: What Matters
- Can You Clean Black Mould Out of Silicone?
- Leaking Shower? How to Tell if It’s the Sealant
- All advice
This guide is general information about sealant work. It isn’t legal, fire-safety or structural advice; for those, speak to a qualified professional.