Blisters are raised spots visible on the surface of a floor, similar in shape to a blister on human skin. How soon after installation a blister develops can help determine the cause. Blisters are also referred to as bubbles.
- Within a few hours, blisters are usually due to a concentration of trapped air. Possible causes:
- Not rolling a floor when it is required; improper rolling
- Placing the flooring into the adhesive too soon; not allowing the proper open time (preset adhesives)
- Irregular subfloor
- Change in atmospheric pressure (may occur at any time)
- At a later time, they often indicate water or vapor pressure in the substrate. Moisture can be present even with a vapor barrier due to punctures in barrier, installing floor before concrete is dry enough, sealer or curing compound on concrete holds water in slab until it eventually breaks down and allows water to escape.
If due to moisture, little can be done. However, if due to moisture because installation was done on green concrete, the slab can be allowed to dry and installation redone. If due to trapped air, puncture blister with a needle or divider point to allow air to escape. If blister is small, it should go down readily by itself. If it is large, the process can be accelerated by heating the area and weighting it down.
Visually, it is better to repair air blisters within the first few days. Injecting additional adhesive under the air blisters is sometimes recommended, but is not always necessary.