Repair
Seams, flashings, drains, and limited membrane patches when the field still has life.
Chicagoland flat roofs
Flat Roof Repair & Replacement in Chicago
Leaks, ponding, bad seams, tired rubber — we inspect, write a clear quote, and install modified bitumen when it’s time to recover or replace.
Licensed & insured · IL #104.019788 · Priority for active leaks
Who this is for
Owners and managers of 2–12 unit flats, courtyard buildings, storefronts, mixed-use, and small commercial roofs across Chicago and the Chicagoland suburbs.
- Water in a unit under the roof
- Ponding after every rain
- Open seams, blistered membrane, cracked flashings
- Clogged drains / scuppers
- End-of-life rubber or coating that’s peeling off
Chicago freeze-thaw and ponding kill flat roofs. We look at the membrane, seams, flashings, and drainage — then tell you repair vs recover vs replace in plain language.
Three options
Repair, recover, or replace
Same building. Different scopes. You get all three in writing after we walk the roof.
Systems
We like to install modified bitumen
Modified bitumen (mod-bit) is our go-to for Chicago flat and low-slope work — tough against freeze-thaw, traffic, and ponding when detailing is right. Why modified bitumen?
We specialize in modified bitumen. We prefer it over TPO for Chicago two-flats, courtyards, and storefronts: tough multi-ply seams, good puncture resistance, and straightforward repairs. On recover and replace jobs, mod-bit is what we install.
How we work
- Inspect — leaks, ponding, membrane, seams, flashing, drainage.
- Written 3-option quote — repair / recover / replace after the walkthrough.
- Schedule — priority for active leaks.
- Protect the building — dry-in and site care while we work.
- Drains & flashings — the details that stop the next leak.
- Walkthrough — you see the finished roof before we leave.
Real job photos
Our modified bitumen installs
Torch work, cover board, deck, and field — real Chicago jobs.
More roofing photos in the gallery
Real job photos from our crews. No stock. No fake reviews.
The material
Why Modified Bitumen?
Modified bitumen (often called “mod bit”) is asphalt that has been upgraded with polymers so it stays flexible and waterproof through temperature swings, freeze-thaw cycles, and normal building movement.
Plain asphalt has been used for waterproofing for over a century, but it gets brittle in the cold and can soften in the heat. That leads to cracking. Modified bitumen solves this by blending special polymers into the asphalt during manufacturing. The result is a tough, flexible membrane made in factory rolls and installed in layers on flat and low-slope roofs.
How the Material Works
There are two main types of polymer modification:
SBS (Styrene-Butadiene-Styrene)
A synthetic rubber. It gives the asphalt elasticity so the membrane can stretch and recover instead of cracking. It stays flexible well below freezing, which makes it especially well-suited for Midwest winters and freeze-thaw cycles.
APP (Atactic Polypropylene)
A plastic modifier. It improves heat and UV resistance and creates a more rigid membrane. It’s often chosen for hotter, sunnier climates.
In the Chicago area, SBS-modified bitumen is the common choice because it handles cold-weather flexibility and thermal movement better.
The modified asphalt is reinforced with a mat (fiberglass, polyester, or a combination) for strength and is typically installed as a multi-layer system (base sheet + cap sheet). The extra layers provide built-in redundancy — if the top layer is damaged, the layer underneath continues to waterproof the roof.
Why It Performs Well on Flat Roofs
- Built for temperature swings. The polymer keeps the membrane flexible through freeze-thaw cycles instead of becoming brittle.
- Multi-layer protection. Overlapping reinforced sheets give redundancy that single-ply membranes don’t have.
- Tough and practical. Strong puncture and foot-traffic resistance. Compatible with standard asphalt repair materials, so maintenance and patches are straightforward.
- Proven track record. Developed in the 1960s as an improvement on traditional built-up roofs and widely used in North America since the late 1970s / early 1980s.
- Installation options. Can be torch-applied, cold-adhered, or self-adhered depending on the product and building requirements.
- Typical lifespan. Often 15–25+ years with proper drainage and maintenance. Good drainage is critical — standing water is the biggest enemy of any flat roof.
Why We Use It
At Xterior Specialists we focus on modified bitumen flat roofs because the material is designed for the conditions we see in the Chicago area: hard winters, freeze-thaw cycles, and the movement that happens on real buildings. Combined with careful detailing (flashings, drainage, and edges), it delivers durable, long-term waterproofing that holds up.
Want to know if mod bit is right for your roof? We’ll walk it and give you a written quote.
Flat roof FAQ
How long does a flat roof last?
A properly installed modified bitumen roof often lasts 15–25+ years with proper drainage and maintenance. Ponding, bad flashings, and ignored seams shorten that fast in Chicago, so we detail drains, edges, and parapet walls carefully.
Can you do emergency leak repairs?
Yes. Active leaks get priority. We stabilize when we can, then quote the lasting fix — repair, recover, or replace.
Insurance vs wear-and-tear?
Storm damage is different from an old roof that wore out. We document what we see. We don’t promise a claim outcome.
What do you check on a flat inspection?
Leaks and stains, ponding, membrane condition, seams, flashings, penetrations, drains and scuppers, and how the roof meets walls and parapets.
Do you only install modified bitumen?
It’s what we install and recommend for Chicago flat roofs. We prefer mod-bit over TPO: multi-ply, torch- or cold-applied seams hold up well to foot traffic, ponding edges, and Chicago freeze-thaw, and it’s easy to repair later.
What is modified bitumen?
Modified bitumen (often called “mod bit”) is asphalt that has been upgraded with polymers so it stays flexible and waterproof through temperature swings, freeze-thaw cycles, and normal building movement.
SBS vs APP?
SBS gives the asphalt elasticity so the membrane can stretch and recover instead of cracking. APP improves heat and UV resistance and creates a more rigid membrane. In the Chicago area, SBS-modified bitumen is the common choice because it handles cold-weather flexibility and thermal movement better.
Service areas
We come to your building
Chicago (including Pilsen and Little Village), Berwyn, Cicero, Oak Park, La Grange, Brookfield, Riverside, Oak Lawn, Summit, and Lyons. If it’s leaking, we work to get there this week.
Chicago
Pilsen
Little Village
Berwyn
Cicero
Oak Park
La Grange
Brookfield
Riverside
Oak Lawn
Summit
Lyons
Need a flat roof looked at this week?
Call to book a leak / ponding inspection. Written quote after we walk the roof.