Description
The Classi Seal Waterproofing Strip (SKU: CS025) is a professional self-adhesive tanking strip designed to create a reliable secondary waterproof seal between shower trays or baths and bathroom walls. Applied before installation, it creates a flexible membrane behind the tiles that accommodates up to 15mm of building movement — providing far superior long-term protection compared to silicone sealant alone. Sold per metre, cut fresh from a 25m roll, so you order exactly what you need with no waste.
📏 Sold per metre — enter the quantity in metres at checkout.For example, quantity 3 = 3 metres, quantity 5 = 5 metres.
How much do you need? Standard shower tray or bath (3 sides): approx. 3–3.5m · Large enclosure: 4–5m · Add 10% for trimming. For a standard pre-cut length, see the
Classi Seal 3.2m Pre-Cut Strip (CS032).
Key Features
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Sold Per Metre — cut to your exact length from a 25m roll; no waste, no offcuts
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Self-Adhesive Backing — pressure-sensitive; quick, clean installation
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15mm Movement Accommodation — flexes with building settlement without compromising the seal
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Tile Immediately — no curing time required after application
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Superior to Silicone Alone — creates a waterproof membrane behind the tiles
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Flexible Strip — conforms to shower tray and bath edges
Technical Specification
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Brand: Classi
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SKU: CS025
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Type: Self-adhesive flexible waterproofing tanking strip
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Sold: Per metre (cut from 25m roll)
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Width: 100–120mm (upstand + base)
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Weight: 0.15kg per metre
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Movement Accommodation: Up to 15mm
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Adhesive: Pressure-sensitive self-adhesive backing
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Material: Flexible waterproof membrane
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Application Temperature: 5°C to 35°C
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Suitable Surfaces: Clean, dry, dust-free
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Maximum Roll Length: 25 metres
How It Works
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Prepare: Ensure tray or bath edges are clean, dry, and dust-free
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Apply: Remove backing and press Classi Seal firmly to the wall-facing edges of the tray or bath
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Position: Install the tray or bath — the upstand extends up the wall
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Tile: Apply tiles over the upstand immediately — no curing wait
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Seal: Apply neutral cure silicone to the bottom edge once tiling is complete
Also Available
Frequently Asked Questions
How do I order the right length?
Enter the number of metres you need as the quantity at checkout. We cut your exact length fresh from a 25m roll. As a guide: a standard shower tray or bath on 3 sides requires approximately 3–3.5 metres. Add 10% for trimming. If in doubt, order slightly more — offcuts can be used for future repairs or smaller projects.
Why use a tanking strip instead of silicone alone?
Silicone sealant is the first line of defence but has limitations — building movement, settlement, and thermal expansion can cause silicone to crack or separate over time. Classi Seal provides a critical secondary barrier: a flexible waterproof membrane behind the tiles that accommodates up to 15mm of movement without failing. Even if the silicone joint cracks, the tanking strip prevents water from reaching the substrate. This dual-layer approach is considered best practice by professional bathroom installers.
Can I tile immediately after applying Classi Seal?
Yes — no curing time is required. Once the strip is applied and the tray or bath is positioned, you can tile over the upstand immediately. The base edge should be sealed with neutral cure silicone once tiling is complete.
What type of silicone should I use?
Always use neutral cure silicone (not acetic/vinegar cure). Acetic cure silicone releases acetic acid during curing which can damage the adhesive and membrane. Neutral cure silicone is widely available and is the correct choice for use with tanking strips and most bathroom materials.
Is there a pre-cut version available?
Yes — the Classi Seal 3.2m Pre-Cut Strip (CS032) is ideal for a single standard shower tray or bath installation with no measuring required. The per-metre option (this product) is best when you need a specific custom length, are completing multiple bathrooms, or want to avoid waste.
Can I order if the item shows as out of stock?
Yes — we can fulfil this product even when stock shows as zero. Place your order as normal and we’ll confirm lead time with you. For urgent enquiries, call us on 01603 381095.
Delivery Information
This is a small, postable item covered by a one-off small item delivery charge. You can combine it with other small items in a single order and pay just one delivery charge. Browse all items covered by the small delivery charge.
