DIY GUIDE · HOME REPAIRS & HANDYMAN · CHECKED 2026-10
How to seal a bath or shower yourself
An hour, plus curing. €42–68 in materials.
An hour's work. The trick is a dry surface, a thin bead and leaving it alone long enough to cure.
- Every step, start to finish
- Checked 2026-10 — sources at the end
- Honest about when to call a pro
FIRST, THE HONEST ANSWER
Do it yourself, or get a handymen?
Do it yourself if…
- The gap is a normal joint between the bath or tray and the tiles
- The tiles and the bath are sound — nothing loose, no movement when you lean on it
- You can get the room dry and keep it unused for a day
- The gap is under about 10 mm wide
Get a pro if…
- The bath or tray MOVES when you lean on it — the seal is the symptom, not the fault
- The gap is wider than about 10 mm, or tiles are loose or drummy
- There is already water damage below: a stained ceiling, a soft floor or a smell
- It is a wet room or a tanked tray, where the failure may be in the waterproofing
Safety first
- Ventilate the room. Curing silicone releases its cure by-product, and silicone remover is a solvent — open the window and keep it open.
- Wear nitrile gloves. Uncured silicone is extremely difficult to remove from skin and remover is harsh on it.
- Keep remover and methylated spirit off your eyes and away from children and pets, and off painted surfaces you care about.
- Mind the knife. Most injuries in this job come from a blade slipping along a wet bath edge — cut away from your other hand.
- Do not put silicone or solvent residue down the drain; let waste cure solid and take solvents to your local civic amenity site (mywaste.ie lists them).
Stop here: the bath moves, or there is damage under it
A bead seals a joint that stays still. If the bath or tray shifts when you lean on it, or there is a stain on the ceiling below, a soft floor or a smell, the sealant is not the fault and sealing over it hides what is. How to hire a sealant applicator →
| MATERIAL | COVERAGE | FOR THIS JOB |
|---|---|---|
| Sanitary silicone, 310 ml cartridge | One cartridge runs roughly 10–12 m of a 6 mm bead | A normal bath needs about 4 m, so one tube does it with margin |
| Silicone remover | One tube or bottle per job | Enough for a bath and a shower tray |
| Methylated spirit | A small bottle lasts several jobs | Used on a cloth, not poured |
| Masking tape | A roll | Two runs the length of the joint |
How much sealant
Cartridges you need: 1 cartridges
1 cartridge — two, so a part-cured nozzle does not stop the job
A 310 ml cartridge gives roughly 11 m at a 6 mm bead and about half that at 10 mm. Measure the joint, do not guess it.
A bath needs a SANITARY grade with a fungicide. General-purpose silicone will go black in a bathroom, and the mould grows inside the bead where you cannot clean it. Read the tube for 'sanitary' or 'bathroom'.
This is the number that matters and it varies by product: Everbuild's Everflex 500 Bath & Sanitary cures at 3 mm per 24 hours with a 10-minute skin time at 20°C; its Showerproof Bathroom Silicone cures at 2 mm per 24 hours with a 15-minute skin time; Forever White gives 2–3 mm in 24 hours at 23°C and 50% humidity; Tecnic S50 gives 3–4 mm per day. A normal bead is several millimetres thick, so 24 hours is a minimum and not a generous one.
Showerproof is rated for application between +5°C and +40°C. A cold bathroom in February cures slower than the tube says, and silicone applied below its minimum may not cure properly at all.
White is standard; clear is more forgiving of a wobbly line because there is less contrast; grey or almond if the grout is dark. A colour you cannot match later means resealing the whole run rather than patching it.
Decorator's caulk is acrylic — paintable, and the right thing where a skirting meets a wall. It is NOT waterproof and must not be used around a bath. If a previous owner used caulk, that is why it failed.
THE PART THAT DECIDES THE FINISH
Preparation, case by case
Silicone sticks to clean, dry, sound surfaces and to nothing else. Find your case and do the preparation; the application is ten minutes.
An old silicone bead, black or peeling
The normal case.
- Cut along both faces with a sharp knife or a stripping tool, then peel the bead away in one piece if you can
- Apply silicone remover to the residue and leave it the time on the tube — scraping unsoftened residue is what scratches a bath
- Scrape with PLASTIC on an acrylic bath; a metal blade leaves marks you cannot polish out
- Wipe the whole joint with methylated spirit and let it flash off; any silicone residue stops the new bead bonding
Acrylic caulk used around a bath by mistake
Common, and it is why the joint failed.
- It comes away more easily than silicone but in crumbs rather than a strip — expect a longer clean-up
- Get every trace out of the corner of the joint with a scraper point
- Wash with warm water to remove the dust, then dry completely
- Finish with methylated spirit; caulk dust is fine enough to stay invisible and still break the bond
Mould in the joint, growing through the bead
Clean it or it comes straight back.
- Remove all the old sealant first — mould lives inside the bead, not on it, so cleaning the surface achieves nothing
- Treat the exposed joint with a bathroom mould cleaner and let it work for the stated time
- Rinse, then dry thoroughly; a joint that looks dry can hold water in the gap
- Use a sanitary grade with a fungicide for the new bead, and run the extractor afterwards
A bath that flexes when you stand in it
Stop — this needs fixing first.
- A flexing bath breaks any seal within months, whatever you use
- An acrylic bath should sit on a supported cradle or board; if it was fitted without one, that is the fault
- Fill the bath with water BEFORE you seal it so it sits at its loaded position, and leave the water in until the silicone has cured
- If it still moves, the bath needs refitting — the sealant is not the job
Tiles that are loose or grout that is missing
The water is already getting past.
- Tap the tiles: a hollow note means the adhesive has let go
- Re-grout missing joints and let the grout cure fully before sealing
- Seal only once the grout has gone off; silicone over green grout traps moisture behind it
- If several tiles are loose, the wall needs attention before any seal will last
A shower tray or wet-room floor
Higher stakes than a bath.
- A tray is usually bedded; if it moves, stop and get it looked at
- Check the upstand and the tanking behind the tiles are intact before resealing
- Dry the tray completely — a tray holds water in the corners long after it looks dry
- Do not use the shower at all during the cure; a bath you can avoid, a shower people forget
THE JOB
How to reseal a bath
Strip the old bead
20 minCut along both faces of the old sealant with a sharp knife or a stripping tool and lift it out, ideally in one length. Work along the joint rather than picking at it.
- Cut both faces before pulling — pulling an uncut bead tears it and leaves the roots behind
- Keep the blade angle shallow against an acrylic bath
- Bag the old bead as you go; it sticks to everything
Mistake to avoid: Trying to scrape it off without cutting it free first. That is how baths get scratched and how roots get left in the corner.
Soften and remove the residue
15 minApply silicone remover over the residue and leave it for the time stated on the tube. Then scrape with a plastic scraper, working the point into the corner of the joint.
- Give the remover its full time — scraping early is what scratches
- Plastic only on acrylic; a metal blade is for tiles and ceramic at most
- Check along the joint at a low angle in good light; residue is easier to feel than to see
Mistake to avoid: Leaving a thin film of old silicone. New silicone will not bond to old, and the bead peels away in a fortnight.
Clean and dry completely
10 min, plus dryingWash the joint, then wipe with methylated spirit or isopropyl alcohol on a cloth and let it flash off. The joint must be bone dry — not towel-dry.
- Methylated spirit rather than water for the final wipe: it lifts residue and evaporates
- Open the window and give it longer than you think, especially in a cold bathroom
- Do not touch the cleaned faces with your fingers afterwards; skin oil is a release agent
Mistake to avoid: Sealing a joint that is still damp in the gap. This is the single commonest reason a new seal fails, and it fails from the back where you cannot see it.
Fill the bath with water
10 minFill the bath to its normal level before you seal, so it sits where it sits when you are in it. Leave the water in until the silicone has cured, then drain it.
- An unloaded bath drops when you get in, and the new bead tears along the top edge
- A shower tray does not need this, but a flexing one needs refitting
- Write yourself a note not to drain it — it is the step people undo by accident
Mistake to avoid: Sealing an empty bath. The bead is then under tension every time it is used, and it splits along one edge within weeks.
Mask both sides of the joint
10 minRun low-tack tape along the tile side and the bath side, leaving the gap you want the finished bead to be. Press the edges down firmly.
- Set the tape to the bead width you want — a 5–6 mm reveal looks right on a bath
- Press the edge down with a fingernail along its whole length
- Keep the two tape lines parallel; the eye reads a tapering bead immediately
Mistake to avoid: Skipping the tape to save ten minutes. Freehand silicone is the difference between a job that looks done and one that looks professional.
Cut the nozzle and lay the bead
10 minCut the nozzle at 45° to about the gap width — small first, you can always cut more. Hold the gun at 45°, start in a corner, and move at a steady speed with steady pressure, pushing the bead ahead of the nozzle rather than dragging it.
- Cut the nozzle smaller than you think and test on paper towel
- One continuous pass per run; stopping and restarting leaves a lump
- Push, do not pull — pushing forces silicone into the joint, pulling lays it on top
Mistake to avoid: Cutting a big hole and laying a fat bead. Too much silicone cures slowly on the inside, tools badly, and stands proud where it catches dirt.
Tool the bead and pull the tape
5 minSmooth the bead in one pass with a profiling tool or a wetted finger, then pull BOTH tape lines immediately, at a shallow angle back on themselves, while the silicone is still soft.
- One pass. Going back over a tooled bead drags it and traps air
- Pull the tape straight away — skin time is 10–15 minutes depending on the product
- Have the bin bag open; taped silicone finds clothing
Mistake to avoid: Leaving the tape until later. Once the surface has skinned, the tape takes the edge of the bead with it and you start again.
Leave it alone to cure
24 hours minimumDo not use the bath or shower. The cure rate on the tube is in millimetres per 24 hours — 2 mm for Showerproof, 3 mm for Everflex 500, 3–4 mm a day for Tecnic S50 — and your bead is thicker than that, so 24 hours is the floor, not the target. Ventilate the room and keep it warm.
- Colder is slower. Showerproof is rated down to +5°C, and at that temperature give it well over a day
- Drain the bath only once it has cured
- Run the extractor, but do not aim a fan at the bead
Mistake to avoid: Showering 'carefully' after a few hours. Water on an uncured bead gets behind it, and the seal is compromised from the first use.
The mistakes that cause nearly every failure
- Sealing a joint that is not bone dry — it fails from behind, where you cannot see it
- Leaving old silicone residue — new silicone does not stick to old
- Sealing an empty bath — the bead splits the first time someone gets in
- Using the bath before the cure time on the tube has passed
Stop here and get a plumber or a tiler
- The bath or tray MOVES when you lean on it — a seal cannot hold a joint that opens and closes, and refitting is the real job
- There is a stain on the ceiling below, a soft floor, or a smell — that is damage that needs finding before it is sealed over
- Tiles are loose or drummy, or grout is missing in several places — the water is already getting past the tiles
- It is a wet room or a tanked tray and the failure might be in the waterproofing rather than the bead
| WHAT YOU SEE | WHY, AND THE FIX |
|---|---|
| The new bead peeled away within weeks | The surface had old silicone residue, or it was damp. There is no repair: strip it, clean back properly with a remover and methylated spirit, dry fully, and do it again. |
| It split along the top edge | The bath was sealed empty and dropped when loaded. Strip it, fill the bath, reseal, and leave the water in until it has cured. |
| The bead went black again quickly | Either a general-purpose silicone was used instead of a sanitary grade, or mould was left in the joint before sealing. Both mean stripping it out and starting with a fungicidal product on a treated joint. |
| The line is lumpy and uneven | The nozzle was cut too big, or the bead was tooled more than once. Strip that run and redo it: a single pass with a smaller hole and tape either side. |
| The tape took the edge off the bead | It was pulled after the surface had skinned. Skin time is 10–15 minutes; pull both lines immediately after tooling. |
| It never fully hardened | Applied below the product's minimum temperature, or the bead is far too thick to cure through. Strip and reapply in a warmer room with a thinner bead. |
| Water is still getting through | The leak is probably not the joint. Check the overflow, the waste connection and the tap tails — a seal gets blamed for all three. |
| There is a stain on the ceiling below | Stop. That is established water damage and the cause may not be the seal at all; it needs looking at before it is covered up. |
WHAT YOU SAVE
What it costs to do it yourself
| Sanitary silicone, two cartridges | €14–22 |
|---|---|
| Silicone remover | €8–12 |
| Skeleton gun, scraper, profiling tool | €12–20 |
| Tape, methylated spirit, gloves | €8–14 |
| Total | €42–68 |
| DIY total | €42–68 |
Guide prices compiled by the Locufy team from published Irish and UK provider price lists and 2026/27 cost guides. Updated 2026.
The tools are a one-off; the second and third time you do this it is the price of a cartridge.
RATHER NOT?
Sealant applicators near you, with prices shown
The ones who cover your area, nearest first, with one score from every review. No account needed to look.
Or post the job free and let them come to you.
Not before. The water is holding the bath where it needs to be while the silicone sets.
Most bathroom mould is a ventilation problem wearing a sealant costume.
Ten seconds with a towel along the seal doubles how long it stays white.
Labelled with the date. Silicone has a shelf life of about a year once opened.
Sealing a bath or shower: questions people ask
At least 24 hours, and the tube tells you why: Everbuild's Everflex 500 cures at 3 mm per 24 hours and its Showerproof at 2 mm per 24 hours. A normal bead is thicker than that, so a day is the minimum — and longer in a cold room, since Showerproof is only rated down to +5°C.
Either it is a general-purpose silicone rather than a sanitary grade with a fungicide, or mould was left in the joint when it was sealed. Mould grows inside the bead, so cleaning the surface does nothing — it has to come out and go back with a sanitary product.
Yes. An empty bath sits higher than a loaded one, so a bead applied empty is stretched every time someone gets in and splits along the top edge. Fill it, seal it, and leave the water in until it has cured.
No. Caulk is acrylic and paintable, which is right where a skirting meets a wall and wrong anywhere near water. If a previous seal was caulk, that is why it failed.
No. Silicone does not bond to cured silicone. It has to be cut out, the residue softened with a remover and scraped off, and the joint wiped with methylated spirit and dried.
A 310 ml cartridge gives roughly 10–12 m of a 6 mm bead and about half that at 10 mm. A standard bath is about 4 m of joint, so one tube does it — buy two, because a part-cured nozzle ends a cartridge.
MORE GUIDES
More DIY guides
Sources — checked 2026-10
- HSA — chemical and hazardous substances: read the safety data sheet, ventilate the room and protect skin and eyes
- MyWaste.ie — household hazardous waste, including solvents
- Everbuild Everflex 500 Bath & Sanitary Silicone — 3 mm per 24 hours, skin time 10 minutes at 20°C
- Everbuild Showerproof Bathroom Silicone — 2 mm per 24 hours, skin time 15 minutes, +5°C to +40°C
- Everbuild Forever White — 2–3 mm in 24 hours at 23°C and 50% RH
- Everbuild Tecnic Silicone S50 — 3–4 mm per day, skin time 15 minutes at 20°C