The Importance Of Routine Maintenance For Flat Roofing In Oakville

Nanzuhzaugewazog still calls itself a town at 230,000+ people, 1 of only 4 places in Canada that size which refuse the word city, and the town has a by-law for the roof the same way it has a by-law for the trees. Most owners of a plaza, a warehouse off the QEW or an office block on Trafalgar have read neither, and both of them are going to decide what happens on the roof this winter.

Oakville’s Property Standards By-law Already Requires A Weathertight, Clean Roof

By-law 2023-074 applies to all property in the town, and section 13 of it is short. A roof and all of its components shall be weathertight, free of leaks and free of loose, unsecured or unsafe objects, damaged roofing has to be repaired or replaced, the roof has to be kept clean and free of debris, and roof drainage may not be discharged onto a walkway, an entrance, a neighbouring property or the road. In the town, then, a flat roof is weathertight by law or it is an Order, and the Order has a price, $100 the second time, $250 the third, $500 for every one after that.

• The maintenance visit is cheaper than the second Order, and it is the only thing that keeps the first one from arriving.

Most of us in Ontario can still call the Elliot Lake mall on the news in June 2012, the rooftop parking deck that had leaked for years and then came down through the food court on a Saturday afternoon, and the inquiry afterwards heard that the owner had known about the roof and chosen not to fix it. That is the picture sitting behind every property standards clause on roofs in this province, and it is why the Oakville by-law bothers to say “loose, unsecured or unsafe objects” as well as “leaks”.

The Tree By-law Keeps The Maples, So The Leaves Land On Your Drains Every October

You cannot take down a tree with a trunk over 15 cm in Oakville without a permit and a visit from the town’s forestry people, which is why the maples along Speers Road and up Trafalgar are still standing over the parking lots, and why they land on the roof drains in the last week of October. A flat roof has 2 or 3 drains on it and each one has a strainer the size of a dinner plate, and 1 wet afternoon of leaves will cover a strainer completely. The water behind it has nowhere to go, so it sits, and a roof carrying standing water is carrying about 10 kg on every square metre for each centimetre of depth, which the deck was never asked to hold for a week.

The 2013 ice storm is the one Oakvillians still measure winters against. The Beaver’s front page that Christmas week had 20,000 Oakville Hydro customers in the dark and the town counting more than 3,000 damaged trees, and the limbs that came down that weekend went onto flat roofs as much as onto cars, where they sat under ice until somebody went up in January.

So the fall visit is mostly a drain visit, booked for the week after the maples drop, and it has to include the overflow scuppers, because a scupper that is blocked is the one that would have saved the deck.

Snow Drifts Against Rooftop Units, And The Code Will Not Let You Count On Shovelling It

Sarnia’s Lambton Mall is the other December Ontario remembers, a store roof that came down under more than 50 cm of snow in 2010 and killed a woman at work before the doors had opened. Oakville gets about 81 cm of snow in a year, 28 cm of it in January, so the even blanket is rarely the problem here, the drift is, because wind off the lake pushes snow across a flat roof until it meets an object standing up, a parapet, an HVAC unit, a skylight curb, and it piles against the windward side of that object at 2 or 3 times the depth on the open deck, so a roof under 20 cm of snow could have 60 cm leaning on 1 unit and the drain for that section sitting underneath it, frozen.

The Ontario Building Code has a line on this drift. Article 4.1.6.14 of Part 4 says the design snow load on a roof may not be reduced on the assumption that the snow will be removed, so the deck was designed to hold the drift, and the question is only whether the drains and the membrane under it have been kept in a state to survive the melt. Where the drift forms on an Oakville roof:

• On the north and east side of every rooftop unit, the lee side of the lake wind.
• Along the inside of the parapet on the side facing the lake.
• In the valley where 2 roof sections meet at different heights, where the upper roof sheds onto the lower.
• Around a skylight curb, which also happens to be the seam most likely to be open.

A Winter Beside The Lake Opens And Closes Every Seam

An Oakville January averages minus 0.4 by day and minus 8.9 at night at the Southeast station, which means the average January day in town goes above freezing in the afternoon and comes back under it before morning. Barrie’s roofs freeze in December and stay frozen. Oakville’s thaw and refreeze, and a seam on a TPO or EPDM membrane that has lifted 2 mm at 1 corner will take water in at 2 in the afternoon and have it turn to ice at 2 in the morning, and the ice is 9% bigger than the water it came from, so the corner lifts a little more, every day, until March. That is the full mechanism behind the leak that appears in April on a roof that was dry in November, and it does not need a storm, only the ordinary rhythm of a winter beside the lake.

Flashing around a vent or a curb does the same thing in metal, the sealant at the top edge cracks on the first hard freeze, the crack takes water on the next mild afternoon, and the water goes under the flashing and into the insulation, where it stays wet and heavy and invisible from above until a thermal camera finds it.

What A Spring And Fall Inspection Should Cover On An Oakville Roof

Twice a year is the standard, and in this town the dates choose themselves, the fall visit after the leaves and before the first hard freeze, the spring visit after the last thaw and before the May rains, with an extra walk after anything like the July 9 storm this year, when the trees came down on Seneca Drive and Seville Crescent in Bronte and Glen Abbey and Highway 5 was shut at Dundas under a fallen tree, because that was a week a lot of flat roofs in town had a branch or a panel on them that did not belong there. Anyone doing commercial roofing in Oakville will have the fall visit booked for the week after the maples drop and will want to be back as soon as the ice has gone.

The fall visit:

• Every drain strainer lifted and cleared, every scupper checked from the parapet side.
• Leaves and branches off the deck, and off the lee side of every rooftop unit.
• The sealant at the top of every flashing pressed with a thumb, and recoated where it has gone hard.
• Seams walked, with a hand run along the laps where the drifts will sit.
• Anything loose on the roof, a satellite dish, a dropped panel, a ladder, tied down or taken down, because the by-law names loose objects.

The spring visit:

• The same drains, because the melt brings down everything the fall missed.
• Blisters and open laps on the membrane where the ice worked all winter.
• Ponding marks, the pale rings left where water stood, each one over a drain that was slow or a low spot that has grown.
• A thermal scan if the roof is more than 15 years old, which finds the wet insulation that a dry surface hides.

From inside the building the roof speaks first, a tea coloured ring on a ceiling tile, paint lifting at the top of a wall, a smell in a stockroom that goes away in a dry week and comes back after rain, and any of those in Oakville is a call to make before the next thaw. The first ring on the tile is the cheapest the repair is ever going to be. Put the fall date in the diary now, for the week the maples finish, and the spring one for the week the last ice leaves the north side of the units.