PC-04
Cap Flashing
Caps the top of a wall so water sheds instead of pooling.
A parapet or freestanding wall has one job at the top: shed water off both faces before it can pool, freeze, and work its way into the wall assembly below. Cap (coping) flashing is what makes that happen.
Cap flashing sits on top of a parapet, freestanding wall, or chimney, formed with a positive slope and hemmed edges so water runs off cleanly instead of sitting on the ledge. It's a small detail that does a lot of work, especially on flat and low-slope commercial roofs, where a leaking parapet cap is one of the most common sources of hidden water damage.
We form cap flashing to your wall width and profile, with splice plates or a continuous cleat depending on the run length and how it needs to perform against wind uplift.
Flat and low-slope commercial roofs are common across Edmonton's industrial and retail buildings, and parapet caps on those roofs take a specific kind of abuse: standing water from spring melt, repeated freeze-thaw right at the cap edge, and wind that gets funnelled and accelerated along a flat roofline. A cap that's pitched correctly and lapped so water always moves toward the outside face, never pools against a seam, is what keeps that water out of the wall assembly instead of finding its way in through a hairline gap.
The choice between snap-lock coping and a surface-fastened cap usually comes down to run length and budget. Snap-lock systems use a continuous concealed cleat, so there are no exposed fasteners for water or wind to work against over time, which is why they're the standard on longer commercial runs. Surface-fastened caps are simpler to install and cost less up front, which makes them a reasonable choice for shorter residential or small-building runs where the extra wind performance of a cleat system isn't needed.
Thermal movement is worth planning for on any long parapet run. Metal expands and contracts with temperature swings across an Alberta year, and a cap that's fastened rigidly along its full length without expansion joints or properly designed splice plates can buckle or pull fasteners loose after a few seasons. We build splice joints that allow for that movement rather than fighting it, so tell us your total run length and we'll lay out the joint spacing accordingly.
Corners are where cap flashing is most likely to fail if they're treated as an afterthought. A mitred corner cut and formed to match the field profile keeps the slope and drip edge continuous around the turn, while a poorly fitted corner patch tends to open a gap right where two runs of water converge. We fabricate corner pieces as part of the same order as your straight runs so the whole cap reads as one continuous system rather than a series of separately sourced parts.
Footage & Piece Calculator
Enter the total run length you need to cover. We'll estimate how many stock-length pieces to order, with a waste allowance for laps and cuts.
Estimate
4
pieces of 10 ft stock
40 ft
total footage to order
Estimate only. Call the shop to confirm before ordering.
Spec Sheet
What You're Ordering
- Materials
- Galvanized or prepainted steel, aluminum on request
- Width range
- Formed to your wall thickness plus overhang, send us the dimension
- Attachment
- Snap-lock coping or surface-fastened, with splice plates or continuous cleat
- Finish
- Mill, galvanized, or prepainted to match your building envelope
Questions
Cap Flashing FAQ
Snap-lock or face-fastened coping, which do I need? +
Snap-lock coping hides all fasteners under a concealed cleat system and holds up better long-term; face-fastened is simpler and less expensive for smaller jobs. We can form either.
How do you handle wind uplift on longer runs? +
Continuous cleats and properly lapped/sealed splice joints are the main defence. Tell us your run length and wall height and we'll spec the joint pattern accordingly.
What width of wall can you cap? +
We form to whatever wall width plus overhang you specify. Send the dimension and we'll quote it.
Can it match the rest of the building's trim? +
Yes, any prepainted colour from our line can be run for cap flashing.
Do you supply the splice plates too? +
Yes, splice plates and corner pieces are formed as part of the same order.
Do I need expansion joints on a long run? +
On most commercial-length runs, yes. We space splice joints to accommodate thermal movement rather than fastening the whole run rigid, which is what prevents buckling as temperatures swing through the year.
Can you form inside and outside corners? +
Yes, mitred or fabricated corner pieces are formed to match your cap profile so the whole parapet reads as one continuous, clean line.
What if the existing cap is leaking, can you help diagnose it? +
Describe what you're seeing, or send photos of the failure point, and we can usually tell you whether it's a lap, seam, or fastening issue before we quote a replacement or repair section.
Do you cap chimneys as well as parapet walls? +
Yes, chimney caps use the same basic principles, positive slope and hemmed edges, just at a smaller scale. Send us the chimney dimensions and we'll form it to fit.
Also See
