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Weatherization Nation 6: Roof Dry-In, Flashing, and Underlayment

Protect the edges from sideways rain, and overlap like you've done it before!
February 24, 2023

Welcome to ProTradeCraft’s Weatherization Nation. A show about building smart from the start.

Last week, we were flashing a window with flexible flashing. We talked about the importance of rolling flashing tapes into their substrates before we stuck the window in the hole and sealed it into the home wrap using flashing tape and smart overlapping.

This week, we’re jumping up on the roof to try out a high-tech underlayment with a no-skid surface.

Before we test out the skid resistance, let’s go to animation land, where it’s always safe and sunny.

Sketch Desk: roof flashing and roofing underlayment installation

First, the team flashed the existing roof with a peel-and-stick membrane before framing the additional roof.

With the new roof framed, we can turn to sealing the critical spots against water infiltration, beginning at the eave and folding the edge of the membrane down over the edge of the roof sheathing. This is a great practice in places with sideways rain or ice dams.

Now, cover the rakes with peel and stick, folding up the existing roof, but not too far. This crotch will be sealed later, and the rake flashing should not extend above the upper edge of the crotch membrane.

But first, we’re going to flash the eave with metal drip edge flashing and install the roofing membrane over it along the bottom edge of the roof.

Cap staples are recommended on this underlayment, every 12 inches along the bottom and every 24 inches in the middle. For high-wind zones, put a fastener everywhere you see a marking on the underlayment.

For all but low-slope roofs, overlap each course four inches and overlap seams six inches.

Now the crotch membrane can seal the intersection of roofs while also sealing the top of the underlayment.

Above that flashing, the underlayment continues to the ridge.

Now we can run drip edge flashing up the rakes, over the edge of Protec underlayment.

Git ‘er Done: Installing Protec roofing underlayment on the roof

Up on the roof, the roofers begin the process. To keep the peel and stick in a straight line, they snap a line to follow.

As he aligns the sheet, he pulls a little piece of the release sheet, which allows him to stick it in place while his partner positions the long end.

He positions the bottom corner, set the sheet on the line, and peels off one side of the split release sheet.

He staples the sheet down to hold it while the adhesive sets up, and he peels off the second release sheet.

Now they can roll out the underlayment.

Because this roof is a lower slope than four in 12, they must overlap the courses significantly, Normal overlap of four inches. For slopes lower than 4, the overlap is 18 inches, half the width of the roll.

He staples the bottom corner, stretches the roll out, and staples it off using button cap staples. Protec will accept regular slap staples if the roof is going to be covered right away.

If you don’t know about hook blades, you should. They are an excellent way to cut roofing products without damaging the layers below.

The guys work their way up the roof to the peak, and they call it a day.

Next Time: Rainscreen on a Roll!

Next week we’re going to jump back off the roof and cover the walls with a high-tech rain screen product called DrainVent.
It creates a drainage space behind the siding so any water that sneaks back there can be directed away from the house.

Previously: Leak-Free Windows

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