Roof
Perimeter and termination conditions where the roof edge needs to stay weather-tight.
Detail libraries
Phase 2 knowledge base
Roof, wall, and valley flashing details explained as a conceptual reference library.
This page gathers the most common envelope transition conditions into one grouped library so estimators and spec reviewers can understand the failure modes before they ask for a fabrication quote.
Reference-only detail. Confirm final dimensions, attachment, and code/manufacturer requirements for the project condition. Need a quote? Use /quote/, call 647-407-0171, or email info@canadianmetalfab.com.
- Grouped by roof, wall, and valley conditions.
- Each detail stays conceptual and fabrication-minded.
- Failure modes and warnings are visible before the handoff.
- Use the library to understand the condition, not to replace project drawings.
Detail context
The page is organized so estimators can find the condition family first, then read the warning signs before a quote discussion.
Reference-only detail
The goal is to help a buyer understand the condition, purpose, failure mode, and fabrication fit of each detail. These are original conceptual diagrams, not stamped project drawings or copied manual pages.
Wall
Transitions where roof water meets a wall, parapet, or projection and needs a clean path.
Valley
Drainage conditions that collect runoff and move it through a shared channel.
Reference-only detail. Confirm final dimensions, attachment, and code/manufacturer requirements for the project condition.
Roof
Roof details
Perimeter and termination conditions where the roof edge needs to stay weather-tight.
roof Conceptual diagram
Roof Edge / Drip Edge
Condition
Perimeter roof termination where runoff needs a clean break from the edge.
Purpose
Direct water away from the eave and protect the edge of the assembly.
Common failure mode
A weak kick, poor fastening, or undersized overhang leaves water tracking back toward the fascia.
Material / thickness note
Commonly formed from 24-26 ga coated steel or stainless when extra durability is required.
Where CMF fabrication fits
Best handled as a project-specific formed trim with the correct hem, leg depth, and drip geometry.
Warnings
- Check compatibility with the panel profile and underlayment sequence.
- Do not treat the profile as a one-size-fits-all standard part.
Reference-only detail. Confirm final dimensions, attachment, and code/manufacturer requirements for the project condition.
roof Conceptual diagram
Gable / Rake Edge
Condition
Sloped roof edge at the rake where wind and rain can load the trim line.
Purpose
Protect the exposed edge and create a durable finish at the roof perimeter.
Common failure mode
Fastener spacing or profile mismatch can leave the edge looking loose or vulnerable to wind uplift.
Material / thickness note
Often specified in 24-26 ga steel or heavier when the exposed edge is long or highly visible.
Where CMF fabrication fits
Custom lengths and profiles help the rake read cleanly against the panel system.
Warnings
- Confirm the rake profile against the actual panel module and slope.
- Detail the termination so the fascia and edge trim do not fight each other.
Reference-only detail. Confirm final dimensions, attachment, and code/manufacturer requirements for the project condition.
roof Conceptual diagram
Penetration / Curb Transition
Condition
Roof opening or curb where equipment, vents, or another projection interrupts the surface.
Purpose
Transition water around the opening cleanly and keep the curb perimeter in control.
Common failure mode
Poor sequencing between curb flashing and counterflashing leaves the opening vulnerable to leaks.
Material / thickness note
Thickness depends heavily on curb height, exposure, and whether the part is visible from grade.
Where CMF fabrication fits
Custom curb flashings and pans are a strong fit when the opening geometry is defined early.
Warnings
- Verify the opening dimensions against the rooftop equipment submittal.
- Treat the curb and flashing package as a coordinated assembly, not separate parts.
Reference-only detail. Confirm final dimensions, attachment, and code/manufacturer requirements for the project condition.
Wall
Wall details
Transitions where roof water meets a wall, parapet, or projection and needs a clean path.
wall Conceptual diagram
Sidewall Flashing
Condition
Roof plane running into a vertical wall along the side of the building.
Purpose
Move water at the roof-to-wall transition and keep the wall line dry.
Common failure mode
Short laps, missing counterflashing, or awkward sequencing can trap water at the joint.
Material / thickness note
Usually formed from 24-26 ga sheet, with heavier material if the wall is exposed or highly visible.
Where CMF fabrication fits
Fabricated step or continuous trim sections should match the wall interface and job sequencing.
Warnings
- Sequence base flashing and counterflashing carefully.
- Check substrate movement and sealant access before locking the profile.
Reference-only detail. Confirm final dimensions, attachment, and code/manufacturer requirements for the project condition.
wall Conceptual diagram
Endwall / Apron Flashing
Condition
Upslope roof plane terminating into a wall or projection at the high end of the run.
Purpose
Carry water away from the wall and keep the termination line from backflowing.
Common failure mode
An undersized apron or poor lap path lets water pool at the upslope termination.
Material / thickness note
Often similar to sidewall flashing, but geometry and leg lengths usually need a custom review.
Where CMF fabrication fits
Project-specific bends and lengths make this a strong fit for fabricated sheet metal.
Warnings
- Confirm the overlap path with the roofing contractor before fabricating.
- If the wall projects forward, check whether the detail needs a longer return leg.
Reference-only detail. Confirm final dimensions, attachment, and code/manufacturer requirements for the project condition.
wall Conceptual diagram
Counterflashing
Condition
Upper protective flashing covering the top edge of a base flashing or reglet.
Purpose
Hide and protect the attachment line and help keep the base flashing watertight.
Common failure mode
Poor substrate attachment or a bad sealant interface can defeat the detail quickly.
Material / thickness note
Typically a moderate-gauge trim piece, but masonry, panel, and curb conditions can call for different stiffness.
Where CMF fabrication fits
Formed counterflashing can be built for masonry reglets, panels, or curb conditions with clean returns.
Warnings
- Do not assume the same attachment method works across all wall assemblies.
- Check whether the project wants a reglet, receiver, or face-mounted approach.
Reference-only detail. Confirm final dimensions, attachment, and code/manufacturer requirements for the project condition.
wall Conceptual diagram
Parapet Coping
Condition
Top of parapet wall where the wall needs to be capped and shed water both sides.
Purpose
Cap the wall, drain water away, and keep the parapet edge from absorbing runoff.
Common failure mode
Flat coping, weak joints, or loose splices can create leak paths and movement issues.
Material / thickness note
Often heavier than edge trim, especially on long runs or when wind exposure is significant.
Where CMF fabrication fits
Coping lengths, splice strategy, and cleat compatibility should be planned together before release.
Warnings
- Check slope and splice strategy before fabricating long lengths.
- Thermal movement matters on larger commercial parapet runs.
Reference-only detail. Confirm final dimensions, attachment, and code/manufacturer requirements for the project condition.
Valley
Valley details
Drainage conditions that collect runoff and move it through a shared channel.
valley Conceptual diagram
Valley Flashing
Condition
Low-side intersection where two sloped roof planes direct runoff into the same channel.
Purpose
Collect and carry water through the valley without letting it spill into the assembly.
Common failure mode
A valley that is too narrow or poorly lapped can overload the drainage path during heavy rain.
Material / thickness note
Can be formed in 24-26 ga steel or thicker where the valley is long, visible, or load-bearing from runoff.
Where CMF fabrication fits
Long formed valley sections and controlled width choices make fabrication fit the actual roof geometry.
Warnings
- Confirm valley width with the roofing system and slope before release.
- Do not rely on a generic photo detail for the final size or lap count.
Reference-only detail. Confirm final dimensions, attachment, and code/manufacturer requirements for the project condition.
Quick spec reference
Typical gauge and material guidance for common flashing conditions. Confirm final specs against the project condition and manufacturer requirements.
| Category | Typical spec | Fabrication note |
|---|---|---|
| Roof edge / drip edge gauge | 24–26 ga coated steel | Lighter gauges suit low-exposure conditions. Increase to 22 ga for long runs or high wind. |
| Wall and parapet gauge | 22–24 ga coated steel | Longer coping and counterflashing runs benefit from stiffer material to hold profile. |
| Valley flashing gauge | 24–26 ga steel or heavier | Match gauge to drainage load and visibility. Heavy runoff valleys may require 22 ga. |
| Aluminum alternative | 0.040–0.063 in | Worth specifying when weight reduction, anodize color match, or galvanic isolation is required. |
| Stainless alternative | 22–26 ga | Specified for extended durability or aggressive corrosion exposure. |
| Lap length | 4–6 in minimum | Confirm with the roofing manufacturer for warranty compliance. |
| Sealant placement | Upslope side of laps | Never fully embed. Leave the downstream edge open to allow drainage. |
Values are reference ranges only. Final gauge, material, and lap call-outs require project-specific review.
Flashing FAQ
These are the questions estimators and spec reviewers most often ask before a fabrication discussion.
What is the difference between base flashing and counterflashing?
Base flashing runs along the roof-to-wall transition and manages water at the surface. Counterflashing sits on top and covers the attachment edge of the base. The two pieces work together as a layered system — each doing a different job.
What gauge is typically used for commercial roof flashing?
24 to 26 gauge coated steel covers most conditions. Longer runs, exposed parapets, or high-wind zones may call for 22 gauge or heavier to keep the profile rigid over the life of the installation.
What causes most flashing failures?
Short laps, inadequate attachment, and sealant applied in the wrong location account for most failures. Thermal movement that was not accounted for in long coping or valley runs is a common secondary cause.
Do the details on this page replace project drawings?
No. These are conceptual reference details. Final dimensions, lap lengths, attachment patterns, and code compliance all require project-specific drawings or manufacturer documentation.
Can the same profile serve as both base flashing and counterflashing?
Not usually. Base flashing and counterflashing have different leg depths, returns, and attachment requirements. Custom fabricating each piece to match the actual condition is almost always the correct approach.
How do I decide between steel and aluminum for a flashing condition?
Galvanized steel is the practical default for most commercial flashing. Aluminum becomes worth considering when weight matters, when a specific anodized color is required, or when galvanic isolation is already built into the assembly design.
Detail check
Need CMF to review a flashing condition with the project team?
Send the roof, wall, or valley condition through the existing quote flow when you want fabrication-minded input. It keeps the next step low-pressure while still giving the detail a real project review.
- Good for trim, coping, curb, and transition questions.
- Keeps the discussion educational before it becomes a quote.
- Useful when the detail needs a fabrication-minded review.
Request a Quote Email info@canadianmetalfab.com
Use /quote/ for the cleanest handoff, or email info@canadianmetalfab.com if that is easier.
For quick contact, use /quote/, call 647-407-0171, or email info@canadianmetalfab.com.
