EPDM Roofing Problems: Ballooning & Blistering Explained (and How to Fix It)
Main Causes of EPDM Ballooning or Blistering
1. Trapped Moisture or Air During Installation
If the substrate wasn’t completely dry when the EPDM was installed—especially in fully-adhered systems—moisture can become sealed underneath. Over time, it evaporates, expands, and creates bubbles or “balloons.” When walked on, these areas often feel spongy or soft.2. Poor Adhesion
A roof membrane relies on strong, even bonding to the substrate. If adhesives were applied unevenly, or if dust, dirt, or humidity interfered during installation, air pockets may form and lead to blistering.3. Vapor Drive from Inside the Building
Without a proper vapor barrier, moisture from inside the building—such as steam from bathrooms, kitchens, or poorly ventilated attics—can rise upward. That vapor pressure can push against the membrane and create blisters, especially in older buildings.4. Improper Substrate or Decking
Porous materials like unsealed wood or fiberboard can gradually release air or moisture. Uneven decking can also create gaps where air becomes trapped, making it difficult for the membrane to adhere properly.What Happens If It’s Not Fixed ?
Blisters may start small but can grow and eventually rupture. This can:- Allow water infiltration, leading to roof leaks.
- Compromise the integrity of the EPDM membrane.
- Increase the risk of wind uplift, since the roofing isn’t fully secured.
How to Fix or Prevent EPDM Blistering
- Inspect and Assess – Determine if blisters are small and dry, or if moisture is trapped inside.
- Small, Dry Blisters – These can sometimes be slit open, dried, re-adhered, and patched with proper seam tape or adhesive.
- Moisture-Filled Blisters – The affected membrane and wet substrate must be removed and replaced before patching.
- Improve Ventilation & Vapor Barriers – Inside the building, ensure proper airflow, insulation, and barriers to control vapor drive.
- For Larger Issues – Widespread blistering may require partial or full re-roofing under corrected conditions.
What This Means for You
EPDM roofing is built to last, but if you notice blistering or ballooning, it’s usually a sign of hidden moisture or installation issues. Catching the problem early can save you from leaks, structural damage, and expensive repairs—while also helping your roof last much longer.To ensure lasting results, work with a licensed roofing contractor who specializes in EPDM systems. Alpha Design Services, a licensed and experienced Maryland roofing contractor, can pinpoint the cause, provide the right repair, and make sure your roof stays strong, secure, and watertight for years to come.
Contact Alpha Design Services today for a free roof inspection and expert advice on keeping your EPDM roof in top condition.
