What’s going on with this Pinhole-Pocked Membrane?

Have you ever seen a membrane look like this? What you’re looking at are tiny bubbles formed due to concrete outgassing. Outgassing happens when air and moisture trapped within concrete escape to the surface, often during the curing process. This leads to pinholes and blisters, which can compromise the membrane’s integrity.

The main causes? Outgassing typically occurs when temperatures rise, increasing the pressure inside the concrete. The warmer it gets, the more air and moisture force their way out. It can also happen when coatings or membranes are applied too early, before the concrete has had a chance to fully dry.

How to prevent it?

• Proper surface preparation: Make sure the concrete has been allowed to fully cure before applying a membrane.
• Control temperatures: Try to apply coatings when temperatures are stable, ideally in the cooler parts of the day.
• Use primers: Primers can help seal the surface, reducing the chances of outgassing. Applying 2 coats of a moisture vapour barrier like WPA 560 will greatly increase your success rate in preventing outgassing from occurring.

While outgassing can be tricky, the right precautions can help prevent these defects and ensure a smooth, long-lasting membrane.

What’s going on with this Natural Stone Surface?

The handy thermal camera reveals there is moisture trapped under this natural stone surface. This causes a 'picture frame effect' as the moisture tries to find its way out of the weakest points, which in this case are the grout joints. In this example, there is a high chance of efflorescence forming. Efflorescence is a crystalline deposit of salts that can form when water is present within certain building surfaces. The probable cause is a rain event prior to grouting the natural stone.