Updated: Nov 23, 2020
Ed is a do-it-yourselfer who is happy to share some of his ideas and experiences in this monthly column.
Howdy, do-it-yourselfers. The title of this month’s article really should be COUNTERflashing, but that didn’t seem like quite as much fun. Counterflashing is the more-or-less permanent metal attached to a house wall or a chimney, and under which step-flashing is used when installing roofing material. (Perhaps I’ll write more on step flashing in another article, another time.) This month’s article is more on “what I did” rather than a “how you should do it” feature. I’ll begin by apologizing to the professionals who actually do this work and do an incredible job. Remember, as a do-it-yourselfer, my goal has always been to do quality work (myself) and save the cost of hiring it out. Sometimes that means the finished product might not be quite as good or as neatly done as work completed by those who have the skills and tools to do things better than I can. What I’m showing you in this article is my way of doing counterflashing. I’ve always admired work by craftsmen who install counterflashing in a “step” arrangement, into the mortar joints between bricks, rather than those whose counterflashing is straight and parallel to the roof line. Here are pictures of the straight type:
And, here’s a picture of the step type, which to me seems inherently more leakproof and certainly has more “appeal” because of the workmanship involved:
In my situation, here are two pictures of the counterflashing (or really, what’s left of it) on the old house I was restoring:
In the second picture, you can see the ladder arrangement I built to provide me a convenient perch from which to work on the counterflashing. This ladder was built “to the slope of the roof” so that each step/seat was level, comfortable, and safe. The top (that you can’t see) has metal pipe arms that reach over the roof peak to hold it in place. With a little research, I learned that the top of each step should have a double-bend in it, permitting that flange to be driven into mortar joints which have been opened up to accept it. See this schematic:
Okay. So that’s the general concept. So what should the steps be made of? In many countries, lead sheets are used. Those would be easily worked, very long-lasting, and corrosion-proof. I don’t think I’d be able to buy lead sheets here in the U.S.! In my case, the “originals” were what I’d just call “tin”, but they obviously have rusted away. If money was no object (wouldn’t THAT be nice!), copper can be used. It looks great new and gradually turns green as it weathers, but remains corrosion-resistant. Copper is $$$! Some folks swear by aluminum, and some swear that you should never use aluminum. From what I’ve learned, painted/treated aluminum holds up well, but raw aluminum reacts with mortar and is short-lived. Stainless steel would also be great but is expensive. What it seems is used a lot in the industry is “terne metal”. This is a thin steel sheet coated with an alloy of lead and tin. I bought a roll through a local roofing contractor, but I’ve found several sources online, and perhaps through specialty stores or those which supply the roofing industry. Here’s the label from the roll:
I don’t have pictures showing work “along the way”, but essentially, with the shapes figured out (using the old locations as “patterns” when possible), cutting and bending the metal, and hammering into the joints, the work went quickly. Where fitment didn’t suit me as being firm enough, I used Tapcon screws and screwed the metal into place to hold it better. Obviously, overlaps needed to be made in the right direction. I then used a black sealant to further caulk all of the joints and to cover any exposed screws. This is what I used, and is what I prefer over several types that I’ve tried (no endorsement implied or intended):
I knew that to ultimately protect things, I’d be painting over these steps, and in the case of the building end, the whole section. Here’s how things looked after caulking:
I did this work before re-roofing, and found that the counterflashing needs to be a bit “up” and “off” the roof to allow enough room to slip the regular step flashing underneath as shingles are applied. So, don’t be so perfect as to get the work too close to the roof or you won’t have enough space to work things under it. Painted up, here’s the end result. (Sorry, but pic against chimney is at a different location…):
I hope all your projects go well. Thanks for reading, and happy restoring!