Modified Bitumen Roofing
Common on older Chicagoland commercial buildings. We know exactly what to do with it.
If your building has a mod-bit or BUR roof, you're not alone. It's one of the most common legacy systems we encounter in the field. Our work starts with understanding what's on your roof, then matching it to the right path: coat, recover, or replace.
Serving the Chicagoland Tri-State AreaAn Asphalt-Based Flat Roof System.
Modified bitumen (mod-bit) is a multi-ply asphalt-based membrane that evolved from traditional built-up roofing (BUR). Polymer modifiers (APP or SBS) are blended with asphalt to create reinforced sheets applied in two or more plies. It was the standard commercial flat-roof specification from the 1970s through the early 2000s and remains on a large share of Chicagoland's older industrial, retail, and institutional buildings.
A typical mod-bit system includes:
- Base sheet: asphalt-impregnated foundation ply
- Modified bitumen membrane: APP or SBS polymer-modified asphalt sheets
- Cap sheet or gravel surfacing: for UV and weather protection
- Flashings: torch or mop-applied details at curbs, edges, and penetrations
What to Do With an Existing Mod-Bit Roof
Every mod-bit roof eventually needs a decision. Which one is right depends on substrate condition, budget, and hold period. Our Proof-of-Value roof inspection gives you the data to choose.
Coat & Restore
If the substrate is structurally sound, a silicone or acrylic coating can extend service life 10-20 years at 25-50% of replacement cost. No tear-off required.
Recover With Modern System
Install a new TPO, EPDM, or standing seam metal system directly over the existing mod-bit (if conditions allow). Eliminates tear-off cost and earns a modern NDL warranty.
Full Tear-Off & Replace
If insulation is wet or the deck is compromised, full tear-off is the right call. Rebuild with insulation, cover board, and your choice of single-ply membrane.
How to Know Your Mod-Bit Needs Attention
When you see any of these, schedule a Proof-of-Value roof inspection before the next storm.
Frequently Asked Questions
Three paths depending on condition. If the substrate is sound, coat it to extend life 10-20 years. If it's aging but deck and insulation are intact, recover it with TPO, EPDM, or standing seam metal. If insulation is wet or the deck is compromised, full tear-off and replacement. Our Proof-of-Value roof inspection determines which path fits your asset.
A well-installed mod-bit system typically delivers 20 to 30 years of service. Many Chicagoland buildings have mod-bit roofs that are already past that window, which is why granule loss, alligatoring, ponding, and leaks become common signs it's time to act.
Yes, if the substrate is structurally sound. Aging mod-bit is one of the best candidates for coating restoration. See our Coatings & Restoration page for qualification criteria.
Depends on the building. TPO is the default for most commercial roofs. PVC if you have grease or chemical exhaust. EPDM on large industrial decks where cost-per-SF matters most. Metal on long-hold assets where eliminating cyclical replacement is a priority. We model cost-per-year for the viable options before specifying.