Flat and low-slope roof repair in Schaumburg

Why split-levels leak at the flat part

The tri-level and bi-level houses built across Weathersfield, Hoffman Estates and Streamwood between 1960 and 1980 usually have one section — over the garage, the family room or a rear addition — with a pitch under 2:12. Asphalt shingles need at least 2:12 to shed water, and 4:12 to do it well. Below that, water sits, wicks up under the shingle edges and finds the nails. Add a winter of snow that never slides off and an ice dam that has nowhere to drain, and you have a very common leak in the northwest suburbs.

The other failure point is the transition, where the shingled upper roof meets the low-slope section. Water coming off the pitched roof lands on the flat one at volume, and if the membrane does not run up under the shingles at least 18 inches with a proper flashing, it goes under both.

EPDM, TPO or modified bitumen: what belongs on a low-slope roof

EPDM rubber. A single black sheet, fully adhered, seamed with tape. A long-time standard for residential flat roofs here. Handles Illinois freeze-thaw well, easy to repair. $8–$14 per square foot installed on a residential section, so a 400 sq ft garage roof runs about $3,500–$5,500.

TPO. White heat-welded membrane. Reflects summer heat, seams are stronger than glued EPDM, a little more expensive. Good on larger sections and where the flat roof is visible from an upstairs window and you do not want black.

Modified bitumen roofing. Torch-down or self-adhered asphalt sheets with a granule surface. Looks the most like a roof, tolerates foot traffic, and is the easiest match to an adjacent shingle roof in color. The two-layer self-adhered system suits the small sections on split-levels.

Shingles don't belong on anything under 2:12, and between 2:12 and 4:12 they need two layers of ice-and-water shield under them. Plenty of roofs in Schaumburg have shingles on a 1:12 slope anyway, often because the last roofer had a bundle left over, and those are the sections that usually end up replaced.

EPDM, TPO and modified bitumen roof repair

A low-slope roof that is under 15 years old with a leak at a seam, a drain, a pipe or the transition is a repair: clean, prime, patch with the matching membrane or a cover strip, reflash the penetration. $300–$900 on most sections, whether it is EPDM, a TPO roof repair in Illinois cold or a modified bitumen patch. Ponding water that stays two days after rain is a slope problem, and the fix is tapered insulation under a new membrane, not another patch. If the section has three patches already and the insulation under it is wet, replacement is the answer, and it should be quoted alongside the pitched roof so the transition is done once. See roof replacement for how the two halves are handled on the same job.

How to check the flat section from a window

• Standing water two days after rain. Ponding means the slope or the drain is wrong.
• Blisters and wrinkles. Bubbles in modified bitumen or wrinkles in EPDM mean the sheet has lost its bond or moisture is trapped under it.
• Open seams. On EPDM, the edge of a lap lifting; on TPO, a seam with a visible gap.
• Shingles on the low slope. If you see tabs instead of a sheet, that section is the likely leak.
• Debris at the drain or scupper. Leaves and shingle grit pile up there and freeze.

Don't walk on it to check unless you know it is sound. A soft deck under a membrane can give way.

What a membrane replacement involves

1. The old covering comes off down to the deck, including any shingles that were laid on it.
2. Soft or rotten decking is cut out and replaced at a per-sheet price.
3. Tapered insulation goes down where water has been ponding, so the section drains toward the edge or the drain.
4. The membrane is laid and adhered, with seams taped (EPDM), heat-welded (TPO) or lapped and sealed (modified bitumen).
5. At the transition, the membrane runs up the pitched roof under the new shingles, with metal flashing over the joint.
6. Edges get new metal trim, and the drain or scupper gets a new flashing collar.

On a typical split-level section this is a one-day job, and it is often done the same day as the pitched roof.

Questions to ask about a flat-roof quote

• Which membrane, and what thickness?
• Is it fully adhered or mechanically fastened?
• Will tapered insulation be added where it ponds?
• How far up the pitched roof will the membrane run at the transition?
• What is the workmanship warranty on the flat section, in writing?
• What does the membrane maker's warranty cover, and does it need registering?

Upkeep that keeps a flat section going

• Clear the drain or scupper each spring and fall, and after big storms.
• Keep the gutters on the upper roof clean, so they don't overflow onto the flat section.
• Trim branches that hang over it; they drop debris and scrape the sheet.
• Keep foot traffic off it, and lay a walk pad where someone has to cross to service an AC unit.
• Look at the seams and the transition once a year from a window, and again after hail.

Small problems on a membrane are cheap to patch early. Left alone, water spreads under the sheet and soaks the insulation, which turns a $300–$900 patch into a replacement.

Small commercial

Small commercial buildings along Golf Road, Roselle Road and in the industrial parks in Elk Grove Village use the same membranes, mostly TPO or EPDM on strip retail and small offices. Commercial flat roofing in Schaumburg, IL is its own trade at the larger end, and owners should ask about commercial experience specifically. The commercial roofing basics post explains what a small business owner should know before getting quotes.

Winter on a flat roof

Snow does not slide off a flat roof. About 37 inches a winter, compacted and refrozen, is a real load on a 1965 garage roof framed with 2x6s at 24 inches, and the melt has nowhere to go but the drain — which is frozen. Clearing a flat section after a heavy storm and heat cable at drains and scuppers that freeze every year are common winter jobs. The ice dam work on the pitched roof and the drain on the flat roof are usually the same problem: a warm attic under a cold edge.