Flat Roof Replacement (Modified Bitumen) in Chicago & Lyons, IL

This page is about full replacement

If your roof has a leak or two, or the membrane is worn but the layers underneath are dry, start with our flat roof repair and recover page. This page covers the bigger job: removing everything to the deck and installing a complete new roof.

When replacement is the right call

• Soft or spongy spots that mean wet insulation or a damaged deck
• Multiple roof layers already in place, so another recover is not an option
• Leaks in several places, or leaks that come back after repair
• Ponding that sits for days because the roof has sagged or drains sit high

What a full tear-off includes

Tear-off to the deck. All old layers come off — the only way to find rot and trapped water.

Deck repairs. Damaged or rotted deck boards are cut out and replaced with new sheathing before anything goes on top.

Insulation and cover board. Rigid insulation goes down over the deck where the scope calls for it, followed by a cover board that gives the membrane a firm, even surface and helps protect the insulation underneath. Boards are mechanically fastened with plates.

Two-ply modified bitumen. A base sheet goes down first, then a granulated cap sheet on top, with laps offset so seams do not line up. Modified bitumen is our preferred system for Chicago flat roofs: two plies give redundancy and it handles freeze-thaw and foot traffic well.

Flashings. Every place the roof meets something else gets new flashing: parapet and roof-to-wall transitions, HVAC curbs, vent pipes, skylights, and roof edges with new metal. Most leaks start at flashings, so this is where we spend the most time.

Drains and scuppers. Drains are reset or replaced and flashed into the new membrane so water leaves the roof.

Combine with masonry work

If the brick at the roof edge needs work, we can pair parapet repair with the replacement so new flashings go onto sound brick.