The type of stain used was Cabot's Semi Solid. The contractor has stated that he would not use that stain again. He's used it on three projects and it has not performed well. It's ability to resist UV is not acceptable.

Thank you very much for the prompt reply! That is very helpful information.

You're welcome! I just spoke with the contractor again and he noted that he'd taken great care to get maximum stain coverage by dipping each shingle and letting them dry before installing them. He said the north side got mildew while the south side stain just disintegrated. He's working with the owners to make it right.

FYI, as we're based in California some of the problem may be due to our focus on low/no VOC's in our products. That can create a problem for manufacturers who are trying to play catch up when new laws negate their earlier formulation recipes.

Thank you! I will look into the VOC regulations in Rhode Island.

Does the person in California have a follow up recommendation for stain - would you use a solid stain with clear primer instead? Or another brand of semi-solid? Please advise!