Adhering Acrylic Shower Walls
What is the best adhesive to bond an acrylic shower wall liner to Villaboard cement sheeting?
Selleys Flexiseal FC Multipurpose Sealant and Adhesive is the product Selleys nominates for this job. It has been formulated for bonding acrylic shower linings to unpainted gypsum plasterboard, cement sheeting and fibre cement wall linings — which is exactly what a Villaboard substrate is — and it is a fast curing product suitable for indoor and outdoor applications. It is often recommended by the manufacturers of shower wall liners themselves, which matters here for a reason covered further down.
The one thing to understand before you buy: Flexiseal FC is a polyurethane adhesive and sealant, not a silicone. That is what gives it the flexibility to hold a large sheet of acrylic against a rigid sheeted wall while both move, and it is also why the working figures below are quite different from the silicone you will use to seal the joints afterwards.
The figures that matter for this job
| Property | Typical result |
|---|---|
| Technology | Polyurethane adhesive/sealant |
| Colour | Grey, black, white |
| Packaging | 310 ml cartridge; 600 ml sausage (varies by colour) |
| Tack free time (23°C, 50% r.h.) | 55–65 minutes |
| Curing rate (23°C, 50% r.h.) | 2.5 mm per 24 hours |
| Joint movement capability | ±25% |
| Elongation at break (DIN 53504) | >550% |
| Application temperature | 5–35°C |
| Service temperature | −40°C to +90°C, with brief points at 120°C |
These are indicative figures only and are not intended for the preparation of specifications. Contact Selleys before using this data to set a specification.
What those numbers mean when you are hanging a liner
The tack free time gives you your working window. At around 55 to 65 minutes in normal conditions, you have time to butter up a full sheet, offer it to the wall and adjust it before the surface starts to set. In a cold bathroom in winter it will be slower, and above 35°C or below 5°C you should not be applying it at all.
The cure rate is the number people misread. At 2.5 mm per 24 hours, a bed of adhesive between a liner and a sheeted wall is not fully cured on day one. Initial bond takes roughly 24 hours; full strength develops over several days. Support or brace the liner until the adhesive has cured, and do not treat a sheet that feels firm as a sheet that is finished.
Flexiseal FC needs atmospheric moisture to cure. That is normal for a polyurethane, and a bathroom supplies it. What it also means is that applying to a substrate carrying high moisture can cause bubbling within the adhesive, so a freshly wet-cut or rain-affected sheet of Villaboard should be dry before you start.
How to apply it
- Check the liner manufacturer's own installation instructions first and follow them where they are more specific than this. Shower liner makers frequently nominate the adhesive and the bead pattern, and they are the party warranting the liner.
- Make sure the sheeting is clean, dry and free of oil, grease, release agents, dust and loose material. Do not apply to a frozen or wet surface, or through standing water.
- Cut the cartridge or sausage, fit the nozzle and load it into a suitable gun. Use a high-thrust gun for a 600 ml sausage.
- Apply Flexiseal FC in spots or beads across the prepared surface, then press the liner firmly into place so the adhesive spreads and makes real contact.
- Use suitable fixing — bracing, props or temporary battens — to hold the liner until the adhesive has cured.
- Seal the perimeter and internal corners afterwards with a silicone suited to a wet area. Do not do this while the adhesive is still curing.
Limitations you need to know before you start
- Do not apply below 5°C air or substrate temperature.
- Not recommended for continuous submersion or below water line use. A shower wall sheds water; it is not immersed, so this is within scope — but a spa or pond is not.
- Do not apply in the presence of curing silicone sealants, as the cure may be affected. This is the practical reason to finish the bonding before you start the sealing, not the other way round.
- Avoid contact with alcohol and other solvent cleaners during cure, which will affect the cure. Methylated spirits on a not-yet-cured bond is a mistake.
- Not for polyethylene or polypropylene without adhesion testing. Most acrylic shower liners are acrylic or ABS, but if yours is a polyolefin sheet, test first.
- Do not use for structural or general glazing.
- Application to substrates with high moisture can cause bubbling within the sealant.
- White may yellow slightly with age and exposure to sun. Behind a liner this is irrelevant; on an exposed bead it is not.
- Flexiseal FC is classified as hazardous and contains isocyanates. Wear gloves and safety glasses.
Clean up and storage
Clean spills and tools with mineral turps before the product cures. Once cured it can only be removed mechanically. Store unopened product below 30°C in a cool dry place out of direct sunlight, and use within 12 months of manufacture. An opened sausage may skin and form a lump near the opening — discard the lump and use the rest.
Common questions about bonding acrylic shower liners
Will Flexiseal FC stick to unpainted Villaboard?
Yes. It is formulated for bonding acrylic shower linings to unpainted gypsum plasterboard, cement sheeting and fibre cement wall linings, and it generally has good adhesion to common building materials without priming.
Do I need a primer?
Generally no. Selleys states Flexiseal FC has good adhesion without priming on the common building materials listed. In some instances a primer may be required, and a pre-test to confirm adhesion is recommended.
How long before I can use the shower?
Selleys does not publish a shower-ready time for Flexiseal FC. The initial bond takes about 24 hours and full strength develops over days at a cure rate of 2.5 mm per 24 hours. The perimeter silicone you apply afterwards will have its own, separate curing requirement — check that product's data sheet.
Can I paint over it?
Painting with water-based paints is possible after curing. If you are using a solvent-based paint, prime first with a water-based primer. Note that it may affect the drying of alkyd or oil-based paints.
Can I silicone the joints at the same time?
No. Do not apply Flexiseal FC in the presence of curing silicone sealants, as the cure may be affected. Bond the liner first and let it cure, then seal.
What colour should I use?
It comes in grey, black and white. Behind a liner the colour is invisible, so choose on availability in the pack size you want.
What size do I need?
310 ml cartridges and 600 ml sausages, with availability varying by colour. A sausage and a sausage gun are the more economical option across a full shower recess.
Is it waterproof?
It is weatherproof and suitable for indoor and outdoor applications, but it is not rated for continuous submersion or below water line use.
How do I clean up excess?
Mineral turps before it cures. Cured Flexiseal FC has to be removed mechanically, so deal with squeeze-out while it is still soft.
Is there anything I should not clean the surface with?
Avoid alcohol and other solvent cleaners during the cure, as they will affect it. Clean and dry the sheeting before you apply, not after.
What question does this Selleys 'Ask an Expert' page address?
The page addresses the question: what is the best adhesive to bond an acrylic shower wall liner to Villaboard cement sheeting?
Which Selleys product is recommended for bonding an acrylic shower wall liner to Villaboard cement sheeting?
Selleys 655 FC Crystal Clear is recommended for bonding an acrylic shower wall liner to Villaboard cement sheeting.
Why is Selleys 655 FC Crystal Clear suitable for this application?
It offers excellent primerless adhesion to cement sheeting substrates, can be applied to wet or damp surfaces (useful in bathrooms), provides a flexible bond to accommodate substrate movement, has a clear finish suited to visible shower liner installations, cures quickly, and offers water resistance for indoor/outdoor and humid conditions.
Can Selleys 655 FC Crystal Clear be applied to damp surfaces?
Yes, Selleys 655 FC Crystal Clear can be applied to wet or damp surfaces, which is beneficial in bathroom environments.
What surface preparation is needed before applying Selleys 655 FC Crystal Clear to Villaboard cement sheeting?
Surfaces should be clean, dry, and free from dust and grease before application, although the product can tolerate damp surfaces.
How much time do you have to tool Selleys 655 FC Crystal Clear before it skins over?
The adhesive should be tooled within approximately 25 minutes before skinning occurs.
Is Selleys 655 FC Crystal Clear suitable for permanent water immersion?
No, Selleys 655 FC Crystal Clear is not recommended for permanent water immersion, so it should be protected from continuous direct water exposure once installed.
What should be done before exposing the installed shower liner joint to water?
Adequate curing time should be allowed before exposing the adhesive to water.
Who publishes this Ask an Expert advice page?
The page is published by Selleys, an Australian adhesives, sealants and fillers brand founded by Martin Selley in 1939 in Sydney, Australia, and a division of DuluxGroup (Australia) Pty Ltd.