When a building has a low-slope roof, homeowners and property managers often hear two common
options: TPO and torch down. Both systems can work, but they are not the same product and they do not
perform the same way on every roof.

What is TPO?

TPO is a single-ply membrane roofing system commonly used on low-slope and commercial roofs. It is
heat-welded at the seams and is known for clean installation, reflective surface options, and broad use on
commercial-style roof assemblies. TPO is often a strong fit when the roof needs a modern membrane
system and the substrate is appropriate for it.

What is torch down?

Torch down is a modified bitumen roofing system installed with heat. It has been used for many years and
can be a reliable low-slope option when installed correctly. It is often selected for smaller low-slope roofs,
certain residential applications, and situations where a multi-layer modified system is preferred.

Main differences

TPO is usually lighter in appearance and often chosen for cleaner, more commercial membrane-style
installations. Torch down is a bitumen-based roof product that has a different look and installation method.
TPO seams are heat welded. Torch down membranes are applied with a torch and rely on proper
membrane bonding, flashing work, and multi-layer assembly details.

Which one lasts longer?

Both systems can perform well when properly matched to the roof and installed correctly. Longevity
depends on drainage, traffic, workmanship, substrate conditions, and maintenance. A bad install can ruin
either system. A good install can give strong service life from either one.

What about foot traffic?

This is a major consideration. Some low-slope roofs are simply weather barriers and not intended for
regular use. Others see service traffic or occasional access. If a roof will see regular foot traffic, the system
should be chosen with that in mind, and in some cases a walkable deck membrane may be more
appropriate than either standard TPO or standard torch down.

What about overlays?

In some projects, an overlay may be considered instead of full tear-off. Whether that makes sense depends on the roof condition, trapped moisture risk, the substrate, drainage, and the type of system already in place. Overlays can sometimes save cost, but they are not always the right choice and should not be used
to hide deeper roof problems.

How to decide

TPO is often attractive for cleaner membrane roofing, broader commercial use, and certain insulation or
low-slope assemblies. Torch down can still be a solid option for the right roof where modified bitumen is a
good fit. The real answer depends on the building, the deck condition, the roof shape, and how the roof is
used.
If you are comparing TPO and torch down for a low-slope roof in Tacoma or the surrounding area, Connelly
Roofing & Gutters can inspect the roof and explain which system makes the most sense for your project.