Mixed-System Roof Project - Flat Membrane + Asphalt Shingle Combination

A lot of LA homes have geometries that need both a flat roof system AND a pitched shingle system on the same property. Original construction with a pitched roof, then a flat-roofed addition off the back. Or a modern remodel that combines a flat main roof with a pitched dormer or garage.

This 14-photo project shows both systems together. The flat section was installed as a single-ply white membrane (Polyfresko) with heat-welded seams and parapet-wall integration. The pitched section was an asphalt shingle install with proper underlayment, step-flashing, and architectural shingles. The transition between the two - where the flat roof meets the rising wall of the pitched section - is the most important detail of the entire project.

At a flat-to-pitched transition, the membrane must lap up the wall and tuck behind the shingle field, with counter-flashing over the top to seal the upper edge. Done wrong, this is where 90% of mixed-system failures happen. Done right, it's invisible and watertight for decades.

Our flat membrane: tear-off of the existing flat-roof assembly, polyiso insulation for code compliance, fully-adhered Polyfresko membrane, heat-welded seams, and welded transitions up onto the parapet and wall surfaces.

Our shingle system: tear-off down to deck, synthetic underlayment, ice-and-water membrane in valleys and at the flat-to-pitched transition, factory-spec step-flashing, and architectural shingles coordinated with the home's exterior.

Fourteen photos cover both systems plus the critical transitions where they meet.