Technical Guidance

Guide To Liquid Waterproofing for Specifiers


The versatility of liquid applied systems means they are now a leading solution for both new build and refurbishment projects. Advances in technology has brought new products to market that can be used for a huge variety of applications, including balconies, walkways, green roof terraces, and pedestrian trafficked podium roofs.

With more specifiers now turning to liquids, the LRWA has produced a new go-to guide offering extensive information and advice to assist with developing specifications.

Drawing on more than 40 years’ experience and extensive research, the LRWA’s Design Guide for Specifiers – Liquid Applied Waterproofing Systems for Roof and Balconies – has been produced by the association’s technical committee, comprising representatives from across our membership, including manufacturers, contractors and associate members.

The Design Guide covers the following areas:

  • Specification and Installation Best Practice
  • Navigating Fire Safety and Performance
  • Understanding Thermal Performance Guidance
  • Optimising Performance

General Advice & Support

liquid-roofing-adviceAll LRWA manufacturer members have dedicated technical advisory staff and are able to provide advice and support including:

  • Specifications
  • Drawings
  • Calculations
  • Site visits if required

For more general enquiries please contact the LRWA Here

Technical Site Support

Competent Roofer

LRWA manufacturer members provide assistance on site either at the request of the contractor or as part of their guarantee procedure. Such site support should be properly documented and any proposed actions followed up and signed off in accordance with the manufacturer’s quality control procedure.

The LRWA are proud to support the NFRC’s Competent Roofer Programme.

Guarantees and Lifespans

All LRWA members must offer a minimum 10 years materials guarantee. Most manufacturers however offer material and workmanship guarantees up to 25 years, based on the system specified under the terms and conditions of their recommended contractor schemes.

The lifespan of the system will usually be well in excess of the guarantee period. In many cases the life of the system can be extended by the application of additional coats at the end of the guarantee period.

Practical things to think about when pricing a project using a liquid applied waterproofing system:

  • The type and condition of the substrate is the only part that can be variable when pricing liquid applied waterproofing. The rougher the substrate the more material will be required. Most manufacturers base specifications on:
    • Smooth – coating onto existing coated surfaces/asphalt or black felt.
    • Medium – Mineral surface felt or easily scabbled surfaces.
    • Rough – Difficult de-chipped roofs or heavy mineral surfaced felt.
  • What type of primer is required if any (dependent on substrate and manufacturer’s recommendations)?
  • Is there a reinforcement required within the liquid applied roofing system that you have chosen?
  • Coverage rate of the topcoat(s) will be specified by the manufacturers.
  • Is the roof clear of obstruction and penetrations?
  • Are there an abundance of obstructions and penetrations (the busier the roof the slower the progress – but using a liquid will be significantly quicker than using a sheet)
  • Thought must be given to the termination details and to any cost considerations that may occur with the provision of chases, trims, termination bars, and mastic pointing.
  • Include for the cost of night seals.
  • Because of the nature of liquid applied waterproofing the waste factor is minimal.

Other General Considerations

For any technical queries please email us at

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