Step Flashings – Code calls for 4 in. legs
Every time I crack my code book I see something I overlooked on the first pass. This morning was no different as I thumbed through the Roof Assembly – Chapter 9 – of the IRC 2009.
Before the 2009 IRC was published the only section that specifically addressed Sidewall Flashing (R905.2.8.4 in the 2006 IRC) said “Flashing against a vertical sidewall shall be by the step-flashing method.” Not a whole lot of detail there. Around where I work in southern New England that meant 5 in. x 7 in. mill finish aluminum cards bent with 2 1/2 in. wall and roof legs. I can’t count the number of times I’ve been called out to fix a roof leak problem that traced back to these puny step flashings.
Hopefully inspectors start enforcing the revised 2009 IRC section (R905.2.8.3) that calls for step flashings with wall and roof legs of 4 in. The extra 1 1/2 in. may not seem like a lot but when you consider that several manufactured sidings require that their product be kept off the roofing surface by 1 in. to 2 in., we need tall wall legs.
I still consider 4 in. legs inadequate and prefer to see a minimum of 5 in. on the wall and 5 in. on the roof. I start with 10 in. square flashing cards made of colored aluminum or copper and gang-bend nice crisp corners on a break. The nice thing about colored metal or copper is that the 1 in. to 2 in. exposed portion doesn’t cause you to squint when the sun reflects off as it will with mill finish aluminum.
And one other notable part of the the Sidewall Flashing section. “At the end of the vertical sidewall the step flashing shall be turned out in a manner that directs water away from the wall and onto the roof and/or gutter.” Wow – they codefied kick out flashings! This is a major major step in keeping water out of walls. For more info on how to install kickout flashings, see the video we did last year:
Or the Kickout Diverter review:
Or the Master Carpenter piece:
5x7 flashing cards don't cut it with the 2009 IRC. The wall and roof legs need to be at least 4 in. (middle flashing). But bigger is better - think 5 in. or more on the wall and roof.