--- title: Why has the flooring/coating got blisters/bubbles in it? (Osmotic Blistering) description: Diagnosis, Causes and Solution to the bubbles, blisters, osmotic, moisture imperfection issues in epoxy resin coating/flooring --- [Skip to content](https://help.resincoat.co.uk/why-has-the-flooring/coating-got-blisters/bubbles-in-it-osmotic-blistering#main-content) - [English](https://help.resincoat.co.uk/why-has-the-flooring/coating-got-blisters/bubbles-in-it-osmotic-blistering) - [Deutsch](https://help.resincoat.co.uk/de/warum-hat-der-bodenbelag/die-beschichtung-blasen-oder-blasenbildung-osmotische-blasenbildung) English Show submenu for translations Open main navigation Close main navigation - - [English](https://help.resincoat.co.uk/why-has-the-flooring/coating-got-blisters/bubbles-in-it-osmotic-blistering) - [Deutsch](https://help.resincoat.co.uk/de/warum-hat-der-bodenbelag/die-beschichtung-blasen-oder-blasenbildung-osmotische-blasenbildung) English Show submenu for translations - [Back to resincoat.co.uk](https://www.resincoat.co.uk/) [Back to resincoat.co.uk](https://www.resincoat.co.uk/) How Can We Help? - There are no suggestions because the search field is empty. 1. [Resincoat Info Hub](https://help.resincoat.co.uk/?hsLang=en) 2. [FAQ](https://help.resincoat.co.uk/faq?hsLang=en) 3. [Potential Issues (and Solutions!)](https://help.resincoat.co.uk/faq?hsLang=en#potential-issues-and-solutions) # Why has the flooring/coating got blisters/bubbles in it? (Osmotic Blistering) ### **What is it?** This is an issue known as “Osmotic Blistering”, often identified by pockets of swelling in the coat of resin paint. ![Osmotic Blistering](https://help.resincoat.co.uk/hs-fs/hubfs/Osmotic%20Blistering.jpg?width=688&height=688&name=Osmotic%20Blistering.jpg) this can occur in an epoxy coating due to moisture, either from rising damp or moisture contamination. ### **Common Causes:** **Lack of preparation -** A poorly prepared concrete surface is the main cause of epoxy blistering, the number one problem associated with this is a bad surface profile. Surface profile is the roughness and porosity of the substrate that allows for a mechanical bond of the epoxy. With all coatings, we would recommend ensuring a Damp Proof Membrane is installed. If you do not have one, you run the risk of rising damp. **Moisture** - Osmotic blistering occurs after the coating has cured, water is pushed up through the substrate but cannot pass through the coating as pressure builds up forming fluid filled blisters. ### **So, how would I resolve this?** - It is recommended that you to sand the coating back, ensuring all blisters are popped to release any water/moisture and rectifying the underlying cause of the damp before recoating. - Applying a damp tolerant primer where there is any residual moisture present is then recommended, the primer will form a bonded layer with the substrate prior to applying the topcoat. - If there is excessive moisture rising from the surface, you may have to consider applying a damp proof membrane, which is a physical sheeting to prevent moisture. - Once the damp-proof membrane is installed and the primer has cured, you will be able to apply the new topcoat. - [Guides](https://help.resincoat.co.uk/guides?hsLang=en#main-content) - [How-To Videos](https://help.resincoat.co.uk/guides?hsLang=en#how-to-videos) - [Application Guides](https://help.resincoat.co.uk/guides?hsLang=en#application-guides) - [Useful Videos](https://help.resincoat.co.uk/guides?hsLang=en#useful-videos) - [Preparation Guide](https://help.resincoat.co.uk/guides?hsLang=en#preparation-guide) - [FAQ](https://help.resincoat.co.uk/faq?hsLang=en#main-content) - [Frequently Asked Questions](https://help.resincoat.co.uk/faq?hsLang=en#frequently-asked-questions) - [Potential Issues (and Solutions!)](https://help.resincoat.co.uk/faq?hsLang=en#potential-issues-and-solutions) - [Gallery & Case Studies](https://help.resincoat.co.uk/gallery-case-studies?hsLang=en#main-content) - [Case Studies](https://help.resincoat.co.uk/gallery-case-studies?hsLang=en#case-studies) - [Product Case Studies](https://help.resincoat.co.uk/gallery-case-studies?hsLang=en#product-case-studies) - [Colour Guides](https://help.resincoat.co.uk/colour-guides?hsLang=en) - [Safety Data Sheets](https://help.resincoat.co.uk/safety-data-sheets?hsLang=en) - [Delivery Information](https://help.resincoat.co.uk/delivery-information?hsLang=en#main-content) - [Delivery Information](https://help.resincoat.co.uk/delivery-information?hsLang=en#delivery-information) - [Returns Policy](https://help.resincoat.co.uk/delivery-information?hsLang=en#returns-policy) [![Chill listening crop-3](https://help.resincoat.co.uk/hs-fs/hubfs/logo_2020_transparent-1.png?width=118&height=24&name=logo_2020_transparent-1.png "Chill listening crop-3")](https://www.resincoat.co.uk) Copyright © 2026, Trade Price Decking