Okay, so I jacked up my porch roof and it was time to replace the roof flashing I removed.

Porch Roof Progress

“So what? … a couple courses of flashing; how big of a deal can that be?”

Well … getting it right is pretty important. I mean – in my experience, it’s the flashing and not the roof that is actually to blame for most leaky roofs. In other words, not getting these little details right can often lead to surely more extensive, and in some cases – very costly, damage.

And with that said, the procedure I used here is very much a hack, I know. In an ideal world, you remove a few courses of siding and place flashing on the side wall behind. I didn’t have that patience here. Read on to see What I Did.

The best action I could have likely taken here would have involved removing a course or two of my siding. Next best, cut in a kerf channel. In either case, I could have tucked my new flashing in and/or behind the siding. Frankly, though, I didn’t want to get into all that. So I had to seek out other options.

Now, as I searched the internet, I could find some very decent articles on the topic. But none spoke directly to my situation. As was the case previously, when I Installed Window and Door Cap Flashing, none applied to a 19th Century farmhouse and flashing to/at wood siding.

Ironically, when I cut open my ceiling, again earlier in the process of jacking up the roof, there were definitely signs of a roof leak/water damage on the porch’s roof deck. So … even though I didn’t have a clear how-to going in, I knew it had to be different than what was previously in place.

What I Did :: Replacing Roof Flashing

First, I took a few minutes and applied a little spray primer to what was essentially bare wood siding. The thinking – this would provide a minimum of protection to the wood that lives behind the flashing.

Next, I installed pre-bent step flashing, weaving into each course of shingles. As with a new roofing install, you start at the bottom of the roof and work upward so that each subsequent course overlaps the one below it. I held each piece of step flashing (in my case measuring 3x4x7) just about 3/8” above the bottom edge of the shingle. Where needed, I trimmed the top edge of the wall leg to fit neatly up under the siding’s lap.

Backer Rod behind Step Flashing

Don’t Forget Kickout Flashing

Prior to installing my steps, I installed a pre-bent kick out flashing – an Amerimax steel product bought at the Home Depot (and installation instructions printed right on the price label – love).

After my last post I received a friendly note from contributor Sean Lintow directing me to a prescriptive article he wrote about, well, roof flashing. He said, “Just saw the jacking up the porch roof post & nice job explaining it & how you did it. I am pretty sure you know to add a kick-out flashing, but just in case you don’t. See Penny Wise – Pound Foolish 2 (Getting Roof Flashing Details Right).

Would This Article Also Help?  Tips and Lessons Learned with Repairing Dutch Lap Wood Siding

kickout diverter

This little bit of metal is sometimes also called a diverter, keeps water from getting behind and moves it to its intended location in the gutter. Absolutely essential in this type of installation.

To give the step flashing a little extra stiffness, I slide some backer rod behind it. I then took a peel and stick flashing (and watch out it can be a little sticky) cut it in half, lengthwise, and applied it to the top edge of my step flashing.

Note: I call this a Grace product, but honestly as it was surplus, I’m not really sure. The point though – this may not have been the exact product I would have used if I were purchasing materials new, it’s just what I had on hand and it would offer a bit of added insurance all the same .

peel and stick flashing over step and diverter flashing

Peel and stick flashing

Nailing the step flashing into the roof shingles. ha! not really a good idea, but the previous set up did this, I did not. For me, the self-seal flashing keep my step flashing where I wanted it.

For counter flashing, I cut and bent mine from a roll of 10″ valley flashing. I used long-cut aviation snips and a pair of hand seamers, first cutting to the pitch of my roof and then bending – 1) a caulk ledge at the top & 2) a one-inch leg and hem at the bottom. This leg is something you’d more likely see with apron flashing (as opposed to on a pitch). For me it didn’t make sense to have the counter flashing just fade into the roofing shingles. (Another Note: I probably could serve myself and redo all of my counter flashing in this area in this manner.)

counter flashing installed

Counter flashing

I used Henry’s 212 behind. DAP 3.0, which I’ve reviewed and is paintable, was used instead at the siding’s and the flashing’s lap at the top and the sides. Though I opted not to smooth it with a finger here.

I finished by lapping this flashing by about an inch and nailing with four each aluminum trim nails. After I painted to match the siding color, and I can report that everything seems to be functioning excellently.

roof flashing at wood siding


I know while not really a sexy project, it’s very important all the same. And while l suspect someone will come along and find issue with how I approached it, I hope it helps. Up next – installing the gutter. Happy Weekend and Happy Home Improving. Thanks. ~jb