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Can you silicone over grout? What you need to know
If you’ve noticed cracked grout around a bath, shower or tiled corner, you may wonder whether you can simply apply silicone over the top.
Sometimes you can. But silicone and grout do different jobs, and putting silicone over grout isn’t always the right solution.
The important question isn’t just whether silicone will stick to grout. It’s whether the joint has been prepared properly and whether silicone is actually the correct material for that particular area.
Can You Put Silicone Over Grout?
Yes, silicone can adhere to some properly prepared grout surfaces. However, that doesn’t mean applying a new bead directly over existing grout is always recommended.
If the grout is loose, crumbling, damp, mouldy or contaminated, the silicone may not bond reliably. Any weakness underneath the new seal can eventually cause the silicone to lift or fail.
In areas where movement is expected, such as changes of plane around a shower or bath, flexible silicone is generally more suitable than rigid grout. But the existing joint still needs to be assessed and prepared properly.
Why Would You Use Silicone Instead of Grout?
The main difference is flexibility.
Grout is primarily used to fill the joints between tiles. Once cured, it forms a relatively rigid surface.
Silicone sealant remains flexible. This allows it to accommodate small amounts of movement between adjoining surfaces.
That makes silicone particularly useful where:
- Two surfaces meet at an angle
- A tiled wall meets a bath
- A tiled wall meets a shower tray
- Wall and floor surfaces meet
- Different materials meet
- Movement is expected
Trying to use rigid grout in a joint that moves can eventually result in cracking.
Should You Silicone Over Grout Around a Bath?
This depends on the condition and design of the existing joint.
If sound grout is present where a flexible seal is required, it may be possible to remove the appropriate section and replace it with silicone rather than simply covering everything with a new bead.
This is particularly relevant around the edge of a bath.
A bath can move slightly when it is filled or when someone gets in. The seal between the bath and tiled wall therefore needs to accommodate that movement.
Applying silicone over loose or deteriorating grout without addressing the underlying joint is unlikely to provide a reliable long-term solution.
Should Shower Corners Be Grouted or Siliconed?
This is one of the most important distinctions.
Internal corners and changes of plane generally need to accommodate movement, which is why flexible sealant is commonly used rather than rigid grout.
For example, where two tiled walls meet inside a shower, the vertical joint is normally grouted. However, the joint between the tiled walls and the shower tray can move as the surrounding materials expand, contract or settle. A flexible silicone sealant is better suited to this type of joint because it can accommodate that movement.
A flexible silicone joint can accommodate this movement more effectively than grout.
That doesn’t mean every tiled joint should be replaced with silicone. Grout remains appropriate for many joints between tiles on the same plane.
The key is understanding what the joint is expected to do.
Can You Silicone Over Cracked Grout?
It’s not usually a good idea to simply cover cracked grout with silicone and assume the problem has been fixed.
Cracked grout can have several causes, including:
- Movement
- Poor installation
- Substrate movement
- Moisture problems
- A failed joint
- Damage to the surrounding materials
If the crack is at a joint that needs flexibility, replacing the rigid grout with an appropriately applied silicone joint may be more suitable.
If the cracking is occurring across ordinary grout joints between tiles, however, the underlying cause should be considered before applying sealant.
What If the Grout Is Mouldy?
Mould is another reason not to simply seal over the existing surface.
Mould growth can indicate persistent moisture, poor ventilation or deterioration of the surrounding materials. If mould has affected the grout or the existing sealant is already failing, the area should be cleaned and assessed properly before new sealant is applied.
Covering a contaminated or damp surface can trap problems underneath the new silicone.
Where existing silicone is heavily mould-stained or deteriorated, it may be more appropriate to remove and replace it completely.
Our guide to why does bathroom silicone turn black? explains some of the common reasons for mould and staining.
Should You Remove Grout Before Applying Silicone?
There isn’t one answer for every situation.
If you’re converting a rigid grout joint into a flexible silicone joint, the appropriate section of grout will generally need to be removed so the silicone can be installed correctly.
Simply applying a thin layer of silicone over a large amount of existing grout may produce a weak or untidy joint.
The aim is to create a joint with enough sealant to perform properly while maintaining good contact with the surrounding surfaces.
Preparation should therefore be based on the particular joint rather than following a one-size-fits-all approach.
How to Prepare a Grout Joint for Silicone
If silicone is the appropriate solution, preparation is critical.
Remove unsuitable material
Loose, cracked or deteriorated grout should be removed where necessary.
If old silicone is already present, it should generally be removed rather than covered.
Clean the surfaces
Remove dust, dirt, soap residue, grease and other contaminants.
Silicone needs a clean surface to achieve reliable adhesion.
Make sure everything is dry
Moisture can interfere with adhesion. Allow the area to dry properly before applying the new sealant.
Check for underlying problems
Look for movement, damaged tiles, water ingress or other issues that could cause the new seal to fail.
Replacing the silicone won’t fix a structural or plumbing problem.
Apply the correct sealant
Use a suitable sanitary silicone or other product appropriate for the application and surrounding materials.
Tool the joint carefully
A properly tooled joint should be smooth, continuous and neatly finished without excessive material spreading across the surrounding surfaces.
For more guidance, see how to apply silicone sealant neatly.
Can You Silicone Over Grout in a Shower?
It can be possible, but the condition of the grout and the purpose of the joint need to be considered first.
If the grout is sound and you’re simply trying to cover it with silicone because it looks tired, that may not be the best approach.
If the joint is a movement joint or a change of plane, replacing unsuitable rigid material with flexible silicone may make more sense.
The important thing is not to treat silicone as a waterproof coating that can simply be painted over everything underneath.
It is a joint sealant, and it needs suitable surfaces and sufficient contact to work properly.
Grout vs Silicone: Which Should You Use?
A simple way to think about it is:
Situation usually more appropriate
- Joint between tiles on the same plane – Grout
- Internal corner between tiled walls – Silicone
- Vertical corners between tiled walls – Grout/Silicone
- Wall meets floor – Silicone
- Bath meets tiled wall – Silicone
- Shower tray meets tiled wall – Silicone
- Joint where movement is expected – Silicone
- General tile-to-tile joint – Grout
There can be exceptions depending on the installation, materials and manufacturer’s recommendations, so the specific construction should always be considered.
Common Mistakes
Applying silicone over dirty grout
Soap residue, dust and other contamination can interfere with adhesion.
Sealing over loose material
If the surface underneath is already failing, the new silicone isn’t going to make it structurally sound.
Using grout where flexibility is needed
Rigid grout can crack when used in joints that experience movement.
Using silicone everywhere
Silicone isn’t a replacement for grout throughout a tiled installation. Using it where grout is intended can create unnecessary maintenance problems and an untidy appearance.
Ignoring the source of moisture
If a joint keeps getting wet because of a leak or installation problem, repeatedly replacing the sealant won’t necessarily solve the underlying issue.
When Should You Replace the Silicone Instead?
If the existing silicone is cracked, peeling, mouldy or separating from the surface, replacing it properly is usually preferable to adding another layer.
The old material should be removed where necessary and the surfaces prepared before the new seal is applied.
You can read more about this in can you apply new silicone over old sealant?.
Getting the Right Finish
Silicone and grout aren’t interchangeable materials. Grout is designed primarily for tile joints, while silicone provides a flexible seal where movement or changes between surfaces need to be accommodated.
If you have cracked grout, failing silicone or a persistent leak around a bath or shower, it’s worth identifying the cause before simply applying another layer of material.
ROSEAL provides professional bathroom resealing and shower resealing for homeowners, landlords and property professionals.
Contact ROSEAL if you need advice or a quotation for professional sealant work.
