Torch Down vs TPO for the Valley Flat Roof in the San Fernando Valley (Part 4)
Choosing between systems in the Valley, with a flat roof as the benchmark, with pitch and exposure taken into account.
Every roofing material works somewhere. The useful question is whether it works here, so this looks at a flat roof against the alternatives in the San Fernando Valley.
What actually matters
Flat roofs are not flat. They are built with fall, and the fall is what keeps them alive. Every other detail is secondary to whether water leaves the roof.
The difference that shows up later
Two systems that cost within a dollar of each other on the quote can differ by a decade in service, and the difference is in the detail rather than the material. Drainage does not fail in the storm; it fails in the eight dry months beforehand. A drain that has been dry since April collects grit, leaves and debris, and nobody looks at it until water is coming through a ceiling. Ask how it is fixed down and how it drains before asking what it costs.
How the San Fernando Valley settles it
Summer is the problem here. The Valley runs ten to fifteen degrees hotter than the coast and holds it for weeks, so a roof surface that reads 90 degrees in Santa Monica is well past 160 in Van Nuys by mid-afternoon. Everything on the roof expands into that heat and contracts again overnight, and it is that daily movement, not the peak temperature, that opens laps and backs fasteners out. Most of the housing went up between 1950 and 1975, which means original decking, undersized ventilation and at least one previous layer that somebody roofed straight over rather than tearing off.
What we look at on an inspection
- Fall across the roof, and any area holding water beyond forty-eight hours
- Drain and scupper clearance, including underneath every strainer
- Membrane condition across the whole field, not only at the edges
- Flashing at every penetration, curb and item of rooftop plant
- Parapet termination and counterflashing along the full perimeter
- Insulation moisture, established by probe rather than by eye
- Evidence and quality of previous patching
Common questions
Can systems be mixed on one property?
Frequently, and on complex roofs it is often the right answer. Low-slope sections and steep sections genuinely want different materials.
Which option is best overall?
There is no overall. There is best for this roof pitch, this exposure and this budget, and those three narrow it down fast.
The honest summary
Ponding, blocked drainage and failed penetration detail account for nearly every flat roof call we take. If a quote does not mention drainage, it is a quote to recreate the same problem in a new material. In the San Fernando Valley the thing to watch is attic temperature and intake ventilation, because a Valley attic that cannot breathe cooks the underside of the roof as hard as the sun cooks the top.
Free inspection, drone photography where access is difficult, and a written estimate with deck repair priced per sheet. No obligation.
More on Flat Roofs
- Torch Down vs TPO for the South Bay Flat Roof in the South Bay (Part 2)Flat Roofs
- Torch Down vs TPO for a Ventura County Flat Roof — Before You CommitFlat Roofs
- Torch Down vs TPO for a LA Flat Roof — Materials ComparedFlat Roofs
- Torch Down vs TPO for a Long Beach Flat Roof — Before You CommitFlat Roofs