Don't reroof. Restore.

The cost-effective, long-term solution for restoration of structurally sound metal roofs


The HydroStop® System

A liquid-applied acrylic elastomeric system for recover and reroof applications.


Want to learn more about HydroStop® before your next project?
Talk to GAF first.



5 Simple Steps to Metal Restoration

with the HydroStop® System

QUICK SPEC  |  CSI SPEC

Step 1: Prep the roof | GAF HydroStop Metal Roof Restoration
Step 2: Prime rust areas | GAF HydroStop Metal Roof Restoration
Step 3: Seal seams | GAF HydroStop Metal Roof Restoration
Step 4: Detail penetrations | GAF HydroStop Metal Roof Restoration
Step 5: Coat the roof | GAF Hydrostop Metal Roof Restoration
The HydroStop System Project Profile | GAF Roofing

1. Prep the roof

  • Ensure the roof is clean, dry, and tight.

  • Make any necessary repairs to the sheet metal. All loose or missing fasteners must be secured or replaced.

  • Power wash the roof using GAF United Cleaning Concentrate (UCC).

  • To divert water away from areas of the roof susceptible to leaks, install sheet metal crickets as needed.

    Application rates:
    Dilute with water at a 1:10 ratio. Apply the diluted cleaning solution to the substrate at the rate of 1.5 Gal/Sq.

2. Prime rust areas

3. Seal seams

4. Detail penetrations

5. Coat the roof

  • Apply HydroStop® Finish Coat per the warranty length. HydroStop offers warranty options of 10, 15, and 20 years. HydroStop FinishCoat can be applied using a brush, roller, or sprayer.

  • A minimum of two coats is required. The second coat should not be applied until the first coat has dried (which can take up to 24 hours). 

    Application rates:
    10 year Warranty: 1.50 Gal/Sq (two coats of .75 Gal/Sq. each coat)
    15 year Warranty: 2 Gal/Sq (two coats of 1 Gal/Sq. each coat)
    20 year Warranty: 3 Gal/Sq (three coats of 1 Gal/Sq. each coat)



5 Products in the HydroStop System

GAF United Cleaning Concentrate (UCC)

For the proper cleaning of existing elastomeric coatings on roofs, metal surfaces, concrete, and masonry substrates as well as uncoated roof, deck, and wall surfaces. UCC Cleaner will help to remove debris from the roof improving adhesion during the application process.

HydroStop Foundation Coat

A water-based acrylic base coat used in conjunction with the HydroStop Fabric. HydroStop FoundationCoat will help improve adhesion to the metal substrate and is the first layer of defense in the HydroStop system.

HydroStop Butter Grade Flashing

A water-based, high-solids elastomeric sealant used to properly seal seams, penetrations and other vulnerable areas of the roof.

GAF Acrylex 400 Primer or LockDown Primer

Acrylex 400 Primer is a water based primer formulated to protect areas of the roof with light rust. LockDown Primer is a Urethane based Primer used to treat more severe rust that is spreading. LockDown Primer protects severely rusted areas and stop them from continuing to rust

HydroStop Finish Coat

HydroStop FinishCoat used in conjunction with HydroStop FoundationCoat, and HydroStop Fabric creates the HydroStop System. It is low VOC, has superior UV, and weather resistance, and is simple to apply and maintain.
*See HydroStop® PremiumCoat® Liquid-Applied Roofing Manual for specific requirements and restrictions.

When you need industry-leading products, training & expertise

Talk to GAF first — from products designed for rooftop efficiency, to dedicated technical support that can facilitate the specification process, to training designed to improve installer productivity, GAF provides solutions to support your business growth and profitability.

To save time, money and hassle on your next roofing project, talk to GAF first.