What material is suggested for sealing membranes to irregular surfaces?

The suggested material for sealing membranes to irregular surfaces is a flexible adhesive. This type of adhesive can accommodate movement and variations in surface texture, which is crucial when dealing with irregularities. Flexible adhesives are designed to create a strong bond while allowing for some expansion or contraction that might occur due to temperature changes or structural shifts.

Other materials such as standard plywood or furring strips lack the necessary flexibility and adaptability to effectively seal irregular surfaces. While acrylic caulk can be useful in certain applications, it may not provide the robust bond required for sealing membranes under various conditions. Therefore, a flexible adhesive is the most suitable choice for ensuring an effective seal on irregular surfaces during a radon mitigation process.