Using Torch down when installing roofing

We have a situation where our builder installed shingles (IKO Cambridge) on a very low slope section of our roof (1/12 pitch) and we had multiple roof leaks as a result. Finally after repeated complaints the builder has agreed to fix it by changing shingles to a torchdown product. They are suggesting specifically CertainTeed Flintlastic SA. We consulted another roofer who suggested using TPO/PVC over torchdown. Does anyone have experience with installing torchdown for low slope roof areas? We are concerned about the life of the product. Any feedback about that specific torchdown product? Would you recommend PVC/TPO over torchdown? Also any issues with having two different products in different sections of the roof?

John Stout answered this question:

Sorry to hear of your leak problems.  It appears that you are well on your way to solving the problem.

CertainTeed FlintLastic SA has a very good reputation. TPO, PVC, and Modified Bitumen are all good roofing systems,

if Properly installed.  The “SA” in CertainTeed refers to the application of the product, the product is Self-Adhered

not Heat Applied or Torched Down.

It is important to have the existing shingle roof removed (from the flat section) and an Approved Roof installed.

I’m sure that the system will give you good service for the life of your Shingle Roof.

It is important to have your roof cleaned of trash and debris and minor maintenance taken care of by  your

Local roofing contractor.