Rooftop Equipment Curbs and Supports in Rockford, IL
Rooftop unit curbs, equipment rails and pipe supports in Rockford, IL, flashed for freeze-thaw and snow, with plain advice on who pays when a unit swap leaks.
Rooftop Equipment Curbs and Supports
Rooftop Equipment Curbs and Supports
Rockford, IL
Snow does not melt evenly on a Rockford roof. It lets go first around the rooftop units, where warm exhaust and dark metal cabinets open little channels, and the water runs straight down the sides of each curb. With about 134 freezing days a year, that meltwater refreezes overnight, builds ice in the corners of the flashing, and lifts the metal a little more with every cycle. By spring the flashing at one corner has pulled off the curb wall, and every rain after that goes through the roof instead of off it. Owners blame the membrane, but the weak spot is often a curb or a support that somebody added years after the roof went on.
Before you sign for equipment work or a repair near a unit, have the curbs and supports looked at as their own line item. They cost little to fix when found early and a great deal when found by a ceiling stain.
Watch what winter does around every unit
A curb is a short box that lifts a rooftop unit above the roof surface so the membrane can run up its sides and tuck under a counterflashing. That makes it the tallest detail on the roof other than the parapet, and it takes the worst of the weather. Wind-driven snow drifts against the upwind side of the curb and sits there into March, which keeps the flashing wet for months. Freeze-thaw cycles work on the corners, where the membrane folds, and a corner bent that often will crack. July does the opposite damage: the cabinet heats and expands against the curb cap, and a sealant that was soft in August is brittle by January.
On a winter walk we check each curb for four things: gaps where the counterflashing no longer touches the curb wall, sealant that has split, rusted fasteners, and ponded water on the uphill side. Any one is a repair you can schedule. All four on one curb usually mean the flashing was built wrong, and our flashing failure repair starts from exactly that finding.
Match the curb to the equipment above it
A prefabricated curb ships with the unit, while a site-built curb is framed by whoever happens to be on the roof that day. Either type has to match the footprint of the cabinet, carry its weight without sagging, and rise high enough that the roofing flashing clears the water and the snow that sits on the roof. A too-short curb leaves flashing at the cap, an easy leak path.
When a unit is replaced, the new cabinet often has a different footprint from the old one. Mechanical contractors solve that with an adapter, and an adapter that is not flashed into the roof becomes a fresh leak path. Rockford follows the 2021 International Mechanical Code, which governs how equipment is installed and reached, so the roofer and the mechanical contractor should agree on clearances before anything is cut. Insulate curb walls to prevent winter condensation. At the Rockton Avenue corridor medical campus or a production roof in Loves Park, a curb leak can interrupt critical work; inspect the flashing and condensate routing together. A hospital roof also needs the drain and equipment curb checked in the same visit.
Get pipes, conduit and supports off the bare membrane
Gas lines, refrigerant lines, conduit and condensate piping all end up on the roof, and they are usually set down by trades who do not roof. A pipe laid straight on the membrane rubs a hole in it as the pipe expands and the roof moves. The better approach is a support that spreads the load, rides on a protection pad bonded to the membrane, and lets the pipe slide.
- Pipe stands or rollers with a pad under each base, spaced so the pipe cannot sag into a low spot.
- Equipment rails that are flashed like curbs, not set on the membrane and screwed through it.
- Pitch pockets and boots only where a better flashing will not fit, with a note to look at them every year.
- Walkway pads wherever service crews cross the roof to reach a unit.
Anything else that goes through the membrane needs its own penetration flashing, not a bead of sealant.
Pay once for the roof work around a unit swap
The easy money mistake is treating the equipment replacement and the roof as two separate jobs. A crane day is expensive, and the roof around the old unit is exposed the moment the cabinet lifts out. If the roofer is not there, the mechanical contractor patches the opening with whatever is on the truck, and you pay a second crew later to undo it. Put the roofer on the same schedule, price the new curb or adapter, the flashing and the membrane repair around it as one scope, and ask for each item on its own line so a change order has nowhere to hide.
If the membrane around the unit is near the end of its life, a swap is the cheapest moment to replace that section, because it is already open. If the rest of the roof has years left, do not let anyone turn a curb job into a replacement upsell. Get the condition in writing from a roof condition report and decide.
Ask these questions before the crane arrives
A few answers up front save an argument later. Put these to the mechanical contractor and the roofer before either one brings equipment up the ladder.
- Who flashes the curb, and who answers if it leaks?
- Does the new unit fit the existing curb, or does it need an adapter?
- Will the roof manufacturer's warranty be affected when someone else cuts the roof, and who calls the manufacturer first?
- Where will the crew stage materials so nothing crushes the membrane?
A 200,000 square foot aircraft maintenance facility like AAR's at Chicago Rockford International Airport is large enough that its curbs, fans and piping deserve a dedicated walk, and so do the five renovated manufacturing buildings in Phase 1B at Colman Yards.
Schedule curb work ahead of the freeze
Sealants and adhesives need dry, mild surfaces, so the best months for curb flashing run from late spring through early autumn. If a unit dies in January, a temporary dry-in around the curb keeps the building dry until the weather lets the permanent detail go on. A spring walk lets you replace tired curbs before the next winter, and a fall visit catches sealant that failed over the summer. A preventive maintenance program puts both visits on the calendar.
Do not wait for a leak to tell you which curb is bad. Snow load and refreezing will find it before you do.
Questions Owners Ask
Who is responsible when a new unit leaks at the curb?
Whoever flashed it. Get that named in writing before the crane is booked, because a leak at a curb is the easiest one for two trades to blame on each other. If the roofer flashes the curb, the roofer owns the leak.
Can a curb be raised without replacing the roof?
Often it can. A taller curb or an extension is framed on the existing deck, the membrane is cut back, and new flashing is tied in around it. The test is the condition of the roof next to the curb, so look at the insulation there before you price the work.
Do I need a roofer present when the HVAC contractor swaps a unit?
Have one there. The moment the old cabinet lifts out, the opening needs a temporary seal, and the new curb flashing has to go in before weather arrives.
How can I tell whether pipe supports are hurting the membrane?
Look for flattened or shiny worn spots under the pipe, standing water pooled at the base of a stand, and wood sleepers that have gone soft. Any of those means the support is wearing the sheet, and a pad or a new stand is a small fix compared with a hole.
What does reflashing a curb cost?
Size, access, curb condition and how much old flashing must come off all move the number, so a fair price comes from a walk on the roof, not a phone call. Ask for each curb priced separately.
