My home has a fiberglass roof deck with parapet wall surrounding it. The parapet wall is covered in aluminum (at least I think its aluminum) that matches the vinyl siding and color of the fiberglass roof deck. There are distinct sections that cover the parapet, and at the seams - in most places - there are small ~3" wide covers. You can see one in the photo here:

Parapet "joint cap"

When we bought the house, for some reason about 4 of these were missing. Which is very strange because we are in a row of 5 houses, all exactly the same, but only our house has these missing, and it's only on the very front wall. So they now look like this:

Missing "joint cap"

And here you can see both a missing one, and others that are in place:

Wider view of seam with and without caps

How can I go about getting something to replace the missing caps? They seem to be aluminum (though I'm not 100% sure). A roofer told me to ask at a building supply store, but they were totally baffled. I can't seem to find anything like this online. In fact, I'm having trouble even figuring out what the call these things. I've found a handful of terms in my research, including:

  • Joint Cap
  • Cap Flashing
  • Cover Plate / Cover Strip
  • ERC Strip (no idea what that stands for)
  • Slip Expansion Cap
  • Slip Cleat
  • Drive Cleat Expansion Joint

But I don't know if any of these are the appropriate term for what I'm looking for, and I haven't been able to find anything that would work to replace these. I'm unable to find any markings on the siding or elsewhere to indicate who might possibly make these (I'm guessing something like that would be under the siding?). I'm at a complete loss on how to replace these things.

Does anyone have any idea how I might find something to replace these? I don't even care if the color doesn't match, because anything would look better than how it looks now.

2 Answers 2


On the jobs I have done like this we used scraps and folded them with duct work pliers (wide flat jaws). If they were fastened at all it would have been on the underside with a small #4 or #6 nail on each side to hold them in place, but usually just a bead of calking to seal the seam and nails that hold them in place. Don’t nail through the top or you have an ugly spot again.

I would check around any place that does siding and take a photo of your material with a white piece of paper in the shot for color balance. They may have some pieces of a similar material and may cut you a couple of strips for $10. I have gotten pieces for next to nothing in the past for being polite and just asking if they have something close. Good luck.


My suggestion is to rent a metal brake. Buy a roll of white aluminum fascia foil. Bend/form a piece of the foil to match the shape to the existing pieces. Cut the formed piece into multiple pieces the width you desire (or to match existing ones). Then caulk the joint and install the new pieces with beads of white silicone underneath the edges (about 3/8" from the edge).

I would rivet the overlaps together on the side and forego the use of nails on the top. Liquid nails should be sufficient to hold them in place.

It seems almost impossible to believe you will be able to find these on a store shelf, pre-made for your dimensions.

  • We don’t use nails on the top of the cap it is there to hide the nails and joint if nailed they are on the underside. We used to use duct forming pliers I just looked and vice grip sells an 8” set for 12$
    – Ed Beal
    Oct 29, 2019 at 21:01
  • 1
    The total cost of what you suggest is around 200 dollars. I’d say that’s a bit high for a few pieces of joint cover
    – Kris
    Oct 29, 2019 at 21:48
  • @EdBeal-- I noticed in his pics there were nails in the top. I don't like that either.
    – peinal
    Oct 30, 2019 at 11:14
  • @Kris- Potentially expensive yes. I just did a quick look on HD site and it is possible to rent the brake and get the metal for ~$100. I am sure prices vary by locale. Hopefully he can find scrap somewhere as isherwood suggests. If not, what other options are available?
    – peinal
    Oct 30, 2019 at 11:26

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