* Product image is for marketing purposes only and may not represent the actual product or colour.
Waterproof Coating & Membrane
S400 Waterproof Coating
Flexible, Fibre-Reinforced Waterproofing
S400 is a flexible, high-performance waterproof coating that can be used as a standalone membrane or reinforced with GeoFabric tape for extra strength across joins, seams, and penetrations. Ideal for roofs, gutters, caravans, tiny homes, and repair work — it's the versatile waterproofing solution at the heart of our DIY range.
Cures to a tough, flexible membrane that moves with the surface and resists cracking over time.
Standalone or Reinforced
Use it on its own as a waterproof coating, or reinforce joins and seams with GeoFabric tape for extra strength.
Versatile Application
Suited to roofs, gutters, caravans, tiny homes, and small repairs — applied by brush, roller, or spray.
Pro & DIY Friendly
Straightforward to apply for confident DIYers, and trusted by professionals for repair and waterproofing work.
03Ideal For
Roofs
Gutters
Caravans
Tiny Homes
Seams & Joins
Small Repairs
Flashings
Waterproofing
04How To Use It
1
Prep The Surface
Make sure the area is clean, dry, and free of dust, grease, moss, and loose material. Treat any biological growth with MuckOff first.
2
Reinforce Joins
For joins, seams, and penetrations, bed GeoFabric tape into a base coat of S400 so it's fully encapsulated once further coats go on.
3
Apply & Build Up
Apply S400 by brush, roller, or spray, building up multiple coats for a continuous waterproof membrane. [Add recommended coats & dry time.]
Why choose S400?
S400 is the workhorse of our DIY waterproofing range. As a flexible, fibre-reinforceable coating it handles everything from a full roof or gutter system to a quick repair on a caravan seam. A 15L pail covers approximately 75–90m² depending on the substrate, and because it can be reinforced with GeoFabric tape across joins and penetrations, you get a genuinely watertight result that moves with the structure rather than cracking as it flexes.
05Frequently Asked
A 15L pail of S400 covers approximately 75–90m², depending on the substrate. Actual coverage varies with the surface's porosity, the number of coats, and the application method.
S400 can be used on its own as a waterproof coating, but for joins, seams, and penetrations we recommend reinforcing with GeoFabric tape. The tape should be fully encapsulated beneath multiple coats of S400 so it's no longer visible.
S400 can be applied by brush, roller, or spray onto a clean, dry, well-prepared surface. [Add recommended number of coats and dry/re-coat time here.] Always follow the product's Technical Data Sheet for best results.
Yes — S400 is a core part of our DIY waterproofing range and is straightforward to apply for confident DIYers, as well as being trusted by professionals. It's also included in our Waterproofing DIY Kits.
Yes — Safety Data Sheets are available on request. Get in touch and we'll send through the relevant documentation for S400.
Get The Full System
Everything You Need To Waterproof
S400 works best as part of a complete waterproofing system. Reinforce with GeoFabric tape across joins and seams, or grab a DIY Kit that includes everything you need for the job.
