On a multi-tenant flex building, the roof is the one asset every tenant shares and no tenant owns, which is why it gets repaired late and bid badly. The fix is a roof plan that assigns every curb, penetration and drain to a unit before anyone calls about a leak. A tilt-up flex building with a parapet on all four sides has to carry the city's 60 psf design snow and 115 mph design wind in full. Send the plans and the sheet. We return a priced scope by bay.
The call: map the roof by unit before the first leak
Riverbend Commerce Park in Post Falls has tilt-up concrete industrial and flex buildings, including a 50,000 square foot warehouse that holds up to five tenants. A building that size can put one roof over as many as five businesses, each with its own rooftop units, vents and skylights. Over time tenants add equipment, and each addition is a hole.
Draw the roof, number every penetration and tie it to a unit. When a leak shows up in bay three, the owner and the tenant both know which curbs sit above it. That one drawing saves a week of arguing and hours of crew time hunting a leak that is not where the stain is.
Add the dimensions and the core results to the same drawing. Where the insulation is wet, shade it. Where the slope is flat, mark the pond. Over a few years, the drawing becomes the building's roof history, and it is the first thing a buyer or lender asks to see. Keep it with the lease file, not in a contractor's drawer, so the next property manager inherits the answer along with the building.
What it costs: tenant turnover, rooftop units and shared drains
The cost drivers on flex space are the penetrations and the schedule. Every rooftop unit is a curb to flash and a shutoff to coordinate. Every tenant change can mean a new unit, a new vent or a relocated line. Price the roof with a unit price per added curb, so the owner knows what a tenant improvement costs the roof before the lease is signed.
Shared drains are the other item. Water from one tenant's bay can run to a drain over another's. We map the drains, check the slope and price any tapered insulation or added drain as an alternate. The owner decides whether to fix the slope now or carry a repair line each spring. That is a cost-and-timing call, and we put both numbers on the page: the one-time price of tapered insulation, and the annual price of patching the same pond for five years.
What the code sheet says: 60 psf, parapets and the frost line
The city sheet rates weathering as severe and adds a 24 inch frost line, and ice barrier underlayment is required where it applies. Roof submittals are checked against that sheet under the statewide 2018 International Building Code.
On a tilt-up building the parapet is the key detail. It holds drifts against the wall, and the through-wall scuppers must be sized and flashed to pass meltwater. Wet snow is dense, so a drift behind a tall parapet loads the roof near the wall far more than the open field. Price the drift check and any added framing as a line.
Where it fails first: scuppers, curbs and the wall joint
Scuppers fail first. They freeze, back water against the parapet and push it under the flashing. Rooftop-unit curbs come next, since each has been flashed by a different trade. Then the joint where the roof meets the tilt-up wall, where sealant dries and the membrane pulls away.
We probe the flashing at every wall and curb and test the drains with a bucket. For a building with several units, a commercial roof inspection before the bid gives the owner a ranked list. Rebuilt rooftop equipment curbs and supports raise the flashing above the drift line and end the repeat leaks.
Light industrial tenants also bring exhaust, make-up air and process vents, and some of those carry heat, fumes or moisture. A vent that discharges against the membrane ages it fast. We check what each tenant vents, look at the membrane around it and recommend a deflector, a taller stack or a protective pad. Those are small lines that prevent a large repair.
Alternates: white membrane, cover board and walkway pads
White TPO single-ply sheds summer heat and is welded at its seams. A cover board resists hail and foot traffic. Walkway pads protect the membrane along the routes service technicians already use. Each is a priced alternate.
We recommend, then let the owner choose. An owner with several buildings can package the alternates across them, the way a warehouse owner does when long runs and few penetrations lower the unit cost. A building with heavy loading activity picks up the dock canopy and truck-traffic details of a distribution center.
Schedule and snow window: one dry season, many tenants
The dry window for roofing is short, with Post Falls seeing about 59 inches of snow a year. A flex building with five tenants needs a schedule each tenant can plan around: which days are loud, which bays have crane access, which doors are blocked. Book in winter, because crews fill with Rathdrum Prairie work from Riverbend Commerce Park to Rathdrum.
Perimeter fastening and tied-down edges at every shift end are priced in the base. For a building along State Highway 41, which runs about 8 miles north from Post Falls to Rathdrum, the delivery route and the crane lane go on the site plan with the schedule.
Tenant moves complicate the calendar. A new tenant who needs a rooftop unit installed the same month as the reroof is a scheduling puzzle, and the answer is to install the curb first, flash it with the new membrane and set the unit afterward. We ask for the tenant improvement calendar at the start and build around it.
Closeout: a roof file that follows the building
The owner gets photographs of every seam, flashing and drain, a roof diagram with penetrations numbered by unit, a punch list and a maintenance schedule. The diagram also shows which drains serve which bays, and which curbs belong to which lease, so when a tenant calls about water, the property manager can name the curb or the drain above that bay before anyone climbs a ladder, and the call becomes a short repair order instead of a long search. The file passes to the next owner or property manager with the building.
Commercial Roofing Questions
How do we stop tenants from damaging the roof?
Require notice before any rooftop work, log every access and add walkway pads on service routes. Price a curb detail for each new unit. A short written roof-access rule in the lease backs it up.
Who pays when a leak affects a different tenant's bay?
That is a lease question. From the roof side, we show which curb or drain caused it, so cost goes to the right place. A numbered diagram and a hose test usually settle it in a day.
Do tilt-up parapets cause more leaks?
They hold drifts and meltwater, so scuppers and wall flashing carry more load. We probe both on every inspection.
Can one roof plan cover several buildings?
Yes. We number each roof, grade its condition and rank the work, so the owner funds the worst roof first. Packaging the work across roofs lowers the cost of crane, mobilization and material per building.
What goes in the closeout file?
Photographs, a numbered roof diagram, the punch list and a maintenance schedule.