Silicone joint coming away from the wall – causes and solution
If the silicone joint comes away from tiles, bath or window frame, the cause almost always lies in the preparation: grease or soap residue, a missing primer on difficult materials or the wrong sealant for the substrate. The remedy is usually the same: remove the old joint without residue, degrease the substrate and let it dry, prime if necessary and regrout with a suitable sanitary silicone.
Contents
What you need
Project template “Renew the silicone joint in the bathroom”If a silicone joint comes away from tiles, bathtub or window frame, the cause almost always lies in the preparation: grease or soap residue on the substrate, a missing primer on difficult materials, or the wrong sealant for the substrate in question. In most cases the solution is the same: remove the old joint without leaving residue, degrease the substrate and let it dry, prime if necessary and seal again with a suitable sanitary silicone.
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Diagnosis: where and how is your joint coming away?
Before you reseal, it is worth taking a close look at the damage. It usually tells you which cause is behind it.
Coming away only in spots or at one corner
Usually a spot under heavy mechanical stress (movement joint, corner) or a spot where soap residue was left behind when the joint was made.
Coming away along the whole length of the joint
Points to a fundamental problem in the preparation of the substrate – usually missing degreasing or a sealant that is not suitable for the substrate.
Joint keeps coming away despite resealing
A strong sign of a difficult substrate (natural stone, plastic, paint) that needs a primer, or of a movement joint with the wrong dimensions.
The most common causes at a glance
| Cause | How to recognise it | Solution |
|---|---|---|
| Grease, soap or silicone residue on the substrate | Joint comes away in a greasy way, often at the edge of the bathtub or shower tray | Remove the old joint completely, clean the substrate free of grease and dust |
| No primer on a difficult substrate (natural stone, plastic bathtub, paint, plastic) | Coming away shortly after curing, although the work was done cleanly | Apply a barrier or adhesion primer before resealing and let it flash off |
| Wrong sealant for the substrate (e.g. standard sanitary silicone on natural stone) | Coming away begins in the edge zones, sometimes with staining | Use a silicone specifically approved for the substrate in question |
| Application outside the permissible temperature (below +5 °C or above +35 °C) | Joint stays soft, tacky or adheres only on the surface | Repeat the resealing within the permissible temperature range according to the manufacturer's figures |
| Movement joint dimensioned wrongly (depth too great in relation to width) | Joint tears preferentially at the bonding faces, often in corners | Reduce the joint depth to about half the joint width, insert a backing profile if necessary |
How to reseal correctly
Remove the old joint completely
First cut the joint out roughly with a sharp knife. Coat the remains with a silicone remover gel, leave it for about 10 minutes and pull it off with the spatula. The substrate has to be dry for this, as moisture deactivates the active ingredients.
Clean the substrate and let it dry
Contact faces have to be clean, free of grease and dust, and sound. Degrease non-porous substrates with a suitable cleaner, and in addition free porous substrates mechanically from loose particles (wire brush, grinding disc).
On a critical substrate: apply a primer
On mineral, absorbent or porous substrates apply a barrier primer thinly and evenly. Be sure to observe a flash-off time of about 30–60 minutes (depending on the substrate) before the joint is made.
Reseal and tool the joint
At an application temperature between +5 °C and +35 °C, apply evenly with the cartridge gun and tool with smoothing agent and a smoothing spatula before a skin forms. Check: the surface must be pore-free and smooth.
Check criterion: Silicone cures through at about 2–3 mm per 24 hours. After the waiting time stated on the cartridge, check discreetly with your fingernail at one spot whether the joint is already firm and no longer tacky before the joint gets wet.
Frequently asked questions
Why is my silicone joint coming away although I worked cleanly?
Usually it is down to invisible residues such as grease, soap or a film of care products on the substrate, or to a substrate that does not offer sufficient adhesion without a primer – for example natural stone, paint or certain plastics.
Do I need a primer for every joint?
No. On ceramic tiles and glass, sanitary silicone as a rule adheres very well even without a primer. On mineral, absorbent or porous substrates, and on natural stone and plastic, a primer improves adhesion considerably.
Can I simply apply new silicone over the old, loosened joint?
No. New silicone does not adhere reliably to old silicone. The old joint has to be removed without leaving residue and the substrate prepared afresh, otherwise the new joint will come away as well.
How long does the new joint have to dry before it may get wet?
Silicone cures through at about 2–3 mm per 24 hours. With a usual joint width you should therefore protect the joint from direct contact with water for at least 24 hours.
Does the joint also come away with the wrong joint geometry?
Yes. If the joint is considerably deeper than it is wide, the sealant cannot stretch sufficiently when there is movement and tears away at the bonding face. As a guide value, a joint depth of about half the joint width applies.
Which silicone is suitable for resealing in the sanitary area?
For the bathroom, kitchen and sanitary area, a sanitary silicone with fungicidal additives such as Ottoseal S100 is suitable, which complies with DIN 18545, part 2, group E.
What you need for resealing
For removing the old joint without leaving residue, the Soudal silicone remover is suitable. On mineral, absorbent or otherwise critical substrates, the Primer 1105 barrier primer improves adhesion before you reseal with Ottoseal S100 Premium sanitary silicone. You will find the complete range of sealants in the category sanitary silicone.
Further guides that go with this one: Removing old silicone without leaving residue, Silicone joint keeps cracking – causes and solution and the step-by-step How to: replace sanitary silicone.
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