TPO, modified bitumen and low slope
Flat and Low Slope RoofingAcross The Triangle.
TPO and modified bitumen for porches, additions and dormers, detailed correctly at the terminations, which is where low slope roofs actually fail. Correct drainage, properly flashed edges.
- TPO membrane
- Modified bitumen
- Ponding correction
- Porch and addition specialists
Free Roof Inspection
Forty five minutes. Every slope photographed. The report is yours whether you hire us or not.
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Flat and Low Slope Roofing done the way it should be
Very few Triangle homes are entirely flat, but a large share have a low slope element: a porch roof, a rear addition, a dormer top, a bay window cap, a garage connection. These are the areas that leak, and they leak because they were built with steep slope materials and steep slope thinking.
Asphalt shingles need pitch to work. Below roughly a 2:12 slope they stop shedding reliably and start relying on the underlayment, which was never designed to be the waterproofing layer. The fix is not better shingles. It is a membrane system designed for water that sits.
Almost every low slope failure we are called to has the same two causes: a termination detail that was never properly flashed, and a drainage plan that does not actually drain. We rebuild both rather than resurfacing over them.
What Flat and Low Slope Roofing Includes
Every line below is in the written scope, not implied by it.
- TPO membrane systems
- Heat welded single ply in white or grey. The welds, not adhesives, make the seams, which is why a properly installed TPO seam outlives the field.
- Modified bitumen
- Torch down and self adhered multi ply, appropriate where foot traffic and mechanical abuse are expected.
- Ponding correction
- Tapered insulation built to actually move water to the drainage point instead of holding it in the middle of the roof.
- Termination and edge detailing
- Wall terminations, counter flashing, drip edge and gravel stop. This is where low slope roofs fail, so this is where we spend the time.
- Scupper, drain and downspout work
- Making sure the water that reaches the edge has somewhere deliberate to go.
- Porch and addition transitions
- The junction between low slope and steep slope, which is the leak point most contractors seal rather than flash.
- Skylight and curb flashing
- Curbs rebuilt and flashed properly rather than buried in sealant.
- Tear off, not overlay
- Existing failed membrane comes off so we can see and correct the substrate underneath.
When Flat and Low Slope Roofing Is The Right Call
- Standing water twenty four hours after rain. Ponding is the defining symptom of low slope failure. Water that sits will eventually find a way through any seam.
- Blisters or bubbles in the surface. Trapped moisture between layers, which expands with heat and pulls seams apart.
- Seams lifting at the edges. Failed adhesive or a failed weld. On an adhered system this is often the beginning of the end.
- Staining on the ceiling below a porch or addition. The single most common low slope call we get in the Triangle.
- Granule loss on a rolled roof. The old rolled asphalt roofs on 1960s and 1970s additions fail this way and are rarely worth repairing.
- Soft spots underfoot. The substrate below the membrane has taken on water and the deck is compromised.
Your Options
What we install, and when each one is actually the right answer.
| Option | Specification | When it fits |
|---|---|---|
| TPO single ply | 60 mil and 80 mil | Our usual recommendation for residential low slope. Heat welded seams, reflective white surface, strong service life in our heat. |
| Modified bitumen | Two ply, torch or self adhered | Where the roof sees foot traffic or mechanical abuse, or where a granulated surface is wanted for appearance. |
| Tapered insulation | Polyiso | Built up to create positive drainage on roofs that were originally built dead flat. |
| Liquid applied flashing | At complex penetrations | For geometry that sheet flashing cannot follow cleanly, used deliberately rather than as a substitute for proper detailing. |
What Flat and Low Slope Roofing Costs
Low slope pricing is driven by area, access, the amount of tapered insulation required and the complexity of terminations. Small porch roofs carry a higher rate per square foot than large open areas because the cost is in the edges.
| Scope | Typical range | Notes |
|---|---|---|
| Porch or bay roof, TPO | Quoted per project | Small area, high proportion of termination detail |
| Rear addition, TPO | Quoted per project | Depending on area and drainage correction |
| Modified bitumen, residential | Quoted per project | Installed, two ply |
| Tapered insulation for ponding | Quoted per project | Added where the existing roof holds water |
| Low slope to steep slope transition rebuild | Quoted per project | Per transition, including flashing |
Financing. Plans including 0% APR options for qualified homeowners, approved in minutes, with no prepayment penalty. Most customers who finance are replacing ahead of failure rather than after it, which is the cheaper moment to do it.
Flat and Low Slope Roofing Across The Triangle
Sixteen towns across Wake, Durham, Orange, Chatham, Johnston and Granville counties.
Other things we do
Flat and Low Slope Roofing Questions
Why does my porch roof keep leaking when the main roof is fine?
Because it is almost certainly shingled at a slope too low for shingles to work. Below roughly 2:12, asphalt shingles stop shedding water reliably and the underlayment becomes the waterproofing, which it was never designed to be. The permanent fix is a membrane system, not another layer of shingles.
How long does a TPO roof last?
Twenty to thirty years for a 60 mil membrane installed correctly with good drainage, and longer for 80 mil. Service life on low slope is governed far more by drainage and detailing than by the membrane itself. A perfect membrane on a roof that ponds will still fail early.
Can you fix ponding without rebuilding the whole roof?
Sometimes, by adding tapered insulation in the ponding area and re terminating locally. Whether that is worth doing depends on the age and condition of the surrounding membrane, and we will tell you when it is cheaper to do the area properly once than to chase it twice.
Is a flat roof more expensive than shingles?
Per square foot, yes, particularly on small areas where most of the cost sits in the terminations. On a small porch the difference in total dollars is modest, and it is the difference between a roof that leaks every few years and one that does not.
Do you do commercial flat roofs?
Yes. Our residential work is the larger share of what we do, but we install and repair TPO and modified bitumen on commercial buildings across the Triangle.
Can a flat roof be walked on?
TPO can take reasonable foot traffic, and where regular access is expected we add walkway pads. Modified bitumen handles traffic better if the roof is genuinely used, for example for equipment access.
Free roof inspection
Find Out What Your
Roof Actually Needs.
Forty five minutes, full photo documentation, and a straight answer, including the answer that you do not need us yet. No obligation, no sales theatre.
307 S. Salem Street, Suite 300 · Apex, NC 27502 · Open 24/7