Monsoon season roof prep: a checklist for Phoenix homes

What monsoon storms do to a Valley roof

Monsoon season officially runs from June 15 to September 30, and it brings a mix of weather that's hard on roofs. Strong outflow winds lift loose tiles and shingles and drive rain sideways under flashing. Haboobs, the big dust storms, coat roofs and clog drains with fine grit. Then a storm cell parks overhead and dumps a lot of rain in a short time, sometimes with hail, testing every weak spot at once.

The roofs that leak during monsoon season usually had a small problem beforehand: a cracked tile, a dried-out sealant joint, a scupper half full of debris. A dry spring hides those problems because there's no rain to reveal them. The point of prepping is to find them while the weather is still calm.

Your ground-level checklist

You don't need to climb on the roof for most of this. In fact, we'd rather you didn't, since tile breaks underfoot and summer roofs are dangerously hot. A pair of binoculars, a walk around the house and a few minutes in the attic will tell you a lot.

Take photos of anything that looks off. If you call us later, those pictures help us figure out what to bring and where to look first.

Do the walk-around in the morning, when the light is low and the roof is still cool enough to look at comfortably. Shadows show slipped tiles and lifted shingle edges better than the flat glare of midday. Check every side of the house, including the narrow side yards most people skip, since those are often where a cracked tile or a clogged downspout has gone unnoticed for years.

• Scan tile and shingle rows for cracks, gaps, slipped pieces or missing ridge caps
• Look at flashing where the roof meets walls, chimneys and parapets for gaps or rust
• Check that scuppers, canales, gutters and downspouts are clear and draining away from the house
• On flat or foam roofs, look for bare foam, blisters or ponding marks from last season
• Trim tree branches that hang over or rub against the roof
• In the attic, look for old water stains, daylight through the deck and damp insulation

Tile roofs: the hidden layer matters most

On a concrete or clay tile roof, a cracked or slipped tile is the visible problem, but the real risk is underneath. Monsoon rain pushed through a gap in the tile lands on the underlayment, which is what actually keeps water out of the house. If that underlayment is 20 years old or more, it may be brittle and cracked, and a storm will find every weak spot. That's why some tile roofs that look perfect still leak in July.

If your tile roof is past 20 years, consider a pre-season check that includes lifting a few tiles at eaves and valleys. Small fixes like replacing broken tiles are quick. If the felt itself is failing, our article on how long tile underlayment lasts explains what comes next.

Flat roofs, parapets and drains

Flat and low-slope roofs are common across the Valley, and their weak points are different. Water has to find its way to scuppers or drains, so anything that blocks them causes ponding. Dust from haboobs, leaves and debris from birds collect at the low spots and turn to sludge with the first storm. Clearing scuppers and drain screens before the season is one of the most useful things you can do.

Parapet walls are the other trouble spot. The cap on top and the flashing where the wall meets the roof take a beating from sun and wind, and cracks there let water run inside the wall. On foam roofs, check whether the coating is thin or worn through. If the surface looks chalky with tan foam showing, a recoat before monsoon season is worth scheduling. Our parapet wall repair page covers what we do when those joints have failed.

Roof-mounted equipment deserves a look as well. AC units, evaporative coolers and their curbs, along with vent pipes and solar mounts, all pierce the roof, and the sealant around them dries out in the heat. A curb that has shifted or a pipe boot that has cracked is an easy entry point for wind-driven rain. Make a note of anything that looks loose, and have it checked along with the drains.

Gutters, scuppers and where the water goes

Many Phoenix homes have partial gutters or none, and that can be fine. What matters is where the water ends up. During a heavy monsoon burst, a roof sheds a surprising amount of water in a few minutes. If it pours off a valley onto your front step, splashes against stucco or soaks the soil next to the slab, it can cause damage that has nothing to do with the roof leaking.

Clear any gutters and downspouts you have, make sure downspouts have extensions or splash blocks, and watch where water lands during the first storm. Grade matters as well. Soil or gravel that slopes toward the house sends runoff straight back to the foundation, so a few minutes with a rake can do as much good as new hardware. If you see a problem spot, adding a short gutter run over that area often fixes it without gutters around the whole house.

When to call a roofer, and what to do during a storm

Call a roofer before the season if you find cracked or missing tiles, flashing gaps, worn coating on a flat roof, past leak stains or an older roof you haven't had looked at in years. Spring scheduling is easier than in August, when crews are booked with storm calls. We're reachable at (602) 878-3594 around the clock, and we'll tell you honestly whether something can wait.

If a leak starts during a storm, move belongings, put a bucket under the drip and, if the ceiling is bulging with water, carefully poke a small hole to let it drain into the bucket rather than letting the drywall give way. Stay off the roof until the storm passes, since wet tile is slick and lightning is common in monsoon cells. Once it's calm, take photos of the ceiling, the attic and anything on the ground that came off the roof, because those pictures help with repairs and with any insurance claim later. Our article on what to do after a monsoon leak walks through the night of the storm and the next morning.

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