SJ-CHRIS:
The 28a has a TPO roof. I confirmed it directly with Thor. Mine's also a 2015 with 116k miles and I had the same thought about dealing with roof maintenance once and for all. I wanted my first season up on the roof to be the last season I'd ever have to go up there again. Collective wisdom found in numerous places around the web led me to go with the Henry 887 100% Silicone Tropi-Cool roof coating and Henry 884 Silicone Roof Seam repair goop, available at most Home Depots (didn't find any at my local Lowes). Lots of videos online to guide you through the experience. Key is doing the prep work thoroughly to ensure the product bonds properly. (But DO NOT USE ACETONE or any petroleum product while cleaning. It will destroy the TPO.) I was concerned about a 50 sq foot area on my roof that was ponding water consistently. The beautiful thing about the Henry is that it is made for this and is 100% waterproof, rain-safe in 15 minutes and lifetime limited warranty. All-in, I probably paid about $500 for product and supplies and applied it myself. My local RV dealer wanted to charge me $5,700 for labor and a comparable 'proprietary' sealant they used, which he would not identify. It was not Dicor. Now I'm not a paid spokesman. I just love how mine worked out, similar to other experiences I've researched. Best wishes however you choose to move forward.
