TPO and Modified Bitumen Flat Roofing for Additions and Outbuildings
Flat and low-slope roofs live or die by their drainage. We design and install TPO and modified bitumen systems that shed water properly, not just membranes laid over a flat deck.
Where Flat Roofing Systems Make Sense
Flat and low-slope roofing shows up on more residential and light-commercial structures than most homeowners expect:
- Home additions — a low-slope roof section that ties into a larger, steeper-slope house.
- Covered porches — flat or nearly-flat sections that need a durable, waterproof membrane.
- Outbuildings — workshops, sheds, and detached structures where a simple, low-maintenance system fits best.
- Ponding water prevention — the single biggest factor in how long a flat roof actually lasts, addressed through slope and drain placement at install.
What a Flat Roof Install Includes
- Deck inspection and slope assessment to identify drainage paths.
- Membrane selection — TPO or modified bitumen — based on the structure and budget.
- Heat-welded or properly sealed seams to prevent water intrusion.
- Drain and edge detailing checked to eliminate low spots that trap water.
Related Services
Flat roofing projects often connect to these services.
Commercial Roofing
Larger-scale low-slope systems for business properties.
Learn more about Commercial RoofingGutter Installation
Drainage that works together with a properly sloped roof.
Learn more about Gutter InstallationRoof Replacement
Full replacement when a flat roof system has failed.
Learn more about Roof ReplacementWhat Is TPO Roofing, Exactly?
TPO — thermoplastic polyolefin — is a single-ply membrane installed in large sheets and heat-welded together at the seams into one continuous, waterproof surface. It's almost always white or light gray, which isn't just cosmetic: that reflectivity bounces summer heat back instead of absorbing it, easing the load on whatever room sits under that flat section.
Installed cost typically runs $4–$10 per square foot on the lower end (up to $17 for thicker, higher-spec membranes), with a 20–30 year expected lifespan depending on membrane thickness and installation quality.
TPO or Standing Seam Metal?
If your property also has pitched roof sections, you may be weighing TPO against standing seam metal for the whole job. We break down cost, lifespan, and hail performance for both in a full side-by-side guide.
Read the TPO vs. Metal GuideFlat Roofing Questions
What is the difference between TPO and modified bitumen?
TPO is a single-ply reflective membrane, heat-welded at the seams, generally lighter and more reflective. Modified bitumen is a multi-layer asphalt-based system, often torch- or heat-applied, and tends to hold up well on smaller or more detailed roof sections. We'll recommend one based on your structure and budget.
Why does ponding water matter on a flat roof?
Water that sits on a flat or low-slope roof for more than 48 hours accelerates membrane wear, stresses seams, and adds weight the structure wasn't built to carry long-term. Proper slope and drainage design during installation is what prevents it.
Can you install flat roofing on a small addition or porch?
Yes, flat and low-slope systems are common on additions, covered porches, and outbuildings where a steep-slope roof isn't practical or doesn't match the structure.
How long does a flat roof system last?
TPO and modified bitumen systems typically last 15 to 25 years depending on the product, installation quality, and how well drainage is maintained. Regular inspection catches seam and ponding issues before they become leaks.
Need a Flat Roof Installed or Repaired?
Free estimate, drainage designed correctly the first time. We serve Fort Worth 76179 and all of Tarrant County.