Cap Flashing (Ridge cap)

Definition: Cap flashing, also known as ridge cap, is a protective barrier installed at the intersection of a roof and vertical surfaces like walls or chimneys. Its main purpose is to deflect water away from these joints, preventing water infiltration.

It’s typically placed over step flashing or kick-out flashing to provide extra protection, ensuring water doesn’t penetrate where different materials meet, such as at roof-wall intersections or around chimneys.

This helps maintain the integrity of the roof and prevents leaks.

Materials of Ridge Cap:

• Metal: Asphalt shingle roofs as well as metal tiles roof with ridge cap are most likely to use metal as the ridge cap material, typically fabricated from galvanised steel, aluminium, copper, or stainless steel. 
• Flexible Membrane: A flexible membrane material might be used in some cases, especially when placed on top of newer roofing systems such as EPDM (formerly known as rubber roofing) or TPO (thermoplastic polyolefin).  

Installation of Cap Flashing:

• Ridge Cap Combined Operation: this flashing is used jointly with step flashing more frequently – under the shingles around a chimney or dormer. Step flashing is run in a stair-step pattern up the slope of the roof, and ridge cap is placed over the step flashing to add protection. 
• Surface Mounting: With ridge caps, you can take it either a step further by having it surface-mounted or by recessing it into a groove (reglet) cut into the vertical surface, by doing this, your cap flash will not move easily and will prevent more water from penetrating into the wall. The edge of your metal piece will usually be caulked (or sealed) with some type of sealant/caulk that will ensure no water gets through.
• Overlap and Secure: The ridge cap (or roofing) should overlap the base flashing to ensure that any water running down the surface goes over the flashing and not behind it. The flashing is then fastened to the substrate by fasteners that are sealant-sealed to avoid leakage.

Ridge Cap Applications:

• Ridge Cap is typically installed around chimneys to seal the joint where it meets the roof, so water can’t get in.
• Roof-Wall Intersections: And also where the roof wall junction (in dormers and parapets).
• Ridge Cap for parapet walls is also an important roof feature that keeps your flat roof dry. Parapet walls are along the perimeter or sides of a flat roof – we’re talking those ‘walls’ that extend upward, like the waist-high walls around the perimeter of commercial and industrial roofs. Without it, the elements will quickly damage this wall, erode it, and cause leaks below.