Waterproofing FAQ’s

Q: How does Isothane EM behave differently from other waterproofing coatings?

A: Isothane EM cures by reaction with atmospheric moisture. In this case urea bonds are formed which promote hydrogen bonding. Water borne or solvent borne coatings dry by evaporation and do not chemically crosslink.  Isothane EM coating is very tough and elastic with multi dimensional stability.

Q: How is Isothane EM affected by atmospheric conditions?

A: Provided that atmospheric moisture is present the coating will cure. However, cold temperatures will show the cure rate and hot temperatures will accelerate it. The application limits are 5°C – 50°C. The moisture curing reaction allows Isothane EM to remain fluid and therefore workable for a long period.  Isothane EM does not change chemically over time once cured. Isothane EM will not embrittle at low temperatures nor will it suffer flow at high temperatures.

Q: Where can Isothane EM be used?

A: Isothane EM adheres well to all standard roofing materials. Isothane EM is immediately waterproof once applied and will not wash off a roof.

Q: What surface preparation is required?

A: All surfaces should be touch dry. Gaps, cracks and voids must be treated with a proprietary mastic or foam filler. Overlaps and upstands should be reinforced with proprietary nylon mesh. Blisters in roofing felt should be made good prior to coating.

Q: What about priming?

A: Isothane PU Prime is a one pack, moisture curing polyurethane primer which promotes adhesion and consolidates porous or friable surfaces.

Q: I need to take advantage of a gap in the weather to complete a job. What is the overcoating time for Isothane EM range?

A: Overcoating may begin as soon as the first coat is cured. This will take between 12 and 48 hours. Isothane PU Primer will be ready to accept a top coat in between 2 and 48 hours, in typical conditions in around 4 hours. Typically, Isothane EMA and EMB will need to be left overnight before overcoating. In the event that more than 72 hours elapses between coats, re-priming with Isothane PU Primer is recommended.

Q: What pot life can I expect from the Isothane EM range, and do you have any tips on storage?

A: As soon as Isothane EM is exposed to atmospheric moisture, it will start to cure and we recommend immediate usage. If a tin is partly used and resealed, a skin will form on the surface which will impede further ingress of moisture. The skin must be removed before use. Any residual Isothane EM in a 25kg pail may be decanted into clean, dry paint tins or similar for use in the future. The tins must be inverted prior to storing.In the event that air enters through the lid the Isothane EM around the lip will cure and impede further ingress of moisture. A 12-month shelf life is quoted for unopened containers.

Q: How do I tackle an area that needs repair, without recoating the whole area?

A: Cut back to a well adhered area. Ensure that the surface is dry and free from dirt, grease and loose materials. Clean the surrounding area with solvent. Prime with Isothane PU Primer. Coat with Isothane EM membrane ensuring that an overlap of 150mm is achieved to the existing material.

Q: Are there any Health & Safety considerations with Isothane EM?

A: All precautions are listed on the relevant Safety Data Sheets.



Need more details?

Call a member of our team +44 (0)1254 872555


Newhouse Road,
Huncoat Industrial Estate,

General Enquiries

Tel: +44 (0)1254 872555Email: info@isothane.com

Sales Enquiries

Tel: +44 (0)1254 872555Email: sales@isothane.com

Technical Enquiries

Tel: +44 (0)1254 872555Email: technical@isothane.com

Prepolymers & Export Enquiries

Tel: +44 (0)1254 872555Email: international@isothane.com


Enter your email to receive latest newsletters and industry updates

This website uses Cookies to improve your browsing experience. View Cookies Policy

I'm fine with this