FlexsoTar - Epoxy / Bitumen Sealer Kit

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Product Overview


FlexsoTar ™ is a high build dense black epoxy/bitumen co-polymer based two pack product. The product sets to render a tough, durable and UV stable gloss black, flexible rubbery finish. This product is non-toxic and can safely be used in applications where it comes into contact with drinkable water.

FlexsoTar ™ is a versatile sealer that can be used in a wide range of applications. Such as:

  • Concrete tile and metal roof repairs: - FlexsoTar™ can be used in conjunction with fibreglass membrane or hemp cloth to form a laminate or on its own for long lasting repairs of leaks, etc.
  • Animal drinking troughs: - FlexsoTar™ can be used on concrete drinking troughs to render a high quality water proof liner. The liner will also protect against moss and will make cleaning effortless.
  • Vehicle undercarriage protection: - FlexsoTar™ will give a long lasting, durable coating on vehicle undercarriages and will prevent rusting.
  • Trailer bins and frames: - renew your trailer with a tough and hard wearing bin coating by applying FlexsoTar™.
  • Steel and metal structures
  • Seal and water proof timber and plywood structures
  • Water proof brick and block work
  • Water proof concrete floors: - FlexsoTar™ can be used under carpets.



  • FlexsoTar ™ is a versatile water proof and surface protection sealer.
  • FlexsoTar ™ is ideally suited for major roof repairs and is compatible with our GilsoFlex ™ roof paint and sealer
  • FlexsoTar ™ is non-corrosive to metals
  • Easy to mix as our kit contains the correct quantities of PART-A (co-polymer) and PART-B (hardener)
  • The pot life is 2 hours and the product will be fully set after 6 hours
  • FlexsoTar ™ can be left as the final finish and does not require further painting.
  • If it is used to repair leaky roofs we recommend a top coat with GilsoFlex ™ Roof sealer and paint.



For more detailed information please see our documents below.

Application Instructions:

Surface preparation:
Ensure the surface to be coated/sealed is dry and clean; remove any old, loose or flaked paint or rust, moss, lichen, old silicone sealer, etc. before application. Rust does not need to be pre-treated and FlexsoTar™ can be applied directly onto rusty surfaces although for best results it is recommended to use our, RUST TREATMENT™, rust converter before application of FlexsoTar™.

Mixing Instructions:
FlexsoTar™ is available in either one (1) litre or two (2) litre quantities. The product is supplied as a two pack system consisting of PART A (Epoxy/Bitumen co-polymer) and PART B (Hardener). Add PART B (entire content) to the can containing PART A (This can is big enough to hold the entire content of PART A and PART B).

Final Finish:
FlexsoTar™ can be left as the final finish and does not require further painting. If it is used to repair leaky roofs we recommend a top coat with GilsoFlex™ Roof sealer and paint.

Clean up:
Clean hands with plenty of soap and water to remove any FlexsoTar™ before gelling occurs. It is recommended to use disposable gloves during application.



These documents contain important information about:

  • Material Safety Data
  • General Information
  • Application
  • Storage
  • Safe use
  • First Aid
  • Clean Up
  • Warranty
  • Available Packing Sizes
  • and more information

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Material Safety Data Sheet (MSDS)

Product Data Sheet (PDS)



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  • 5

    Posted by John on 11th Apr 2022

    Excellent product - does exactly what it claims to do. Really great customer service. !!!!

  • 5
    Great for repairs & excellent customer service

    Posted by Lucia on 8th Mar 2022

    I came across BioSymph products when researching how to fix my flat roof extension. I had some rust issues and the flashing was failing allowing water in. During my first repair attempt, I ran out of usable product before I'd finished because the product set more quickly than expected. Pierre responded very promptly with great advice, revised instructions and a free replacement. I've now completed the repairs and no more leaks! Always happy to support NZ made products, and when it comes with excellent customer service it's even better.