COP:penetrations; collar-or-boot-flashings

8.4 Collar Or Boot Flashings 

Proprietary EPDM pipe flashings are in common use in NZ but they have some disadvantages.
  • They are lapped over the roof cladding, creating a dam that holds moisture and dirt.
  • They rely on sealant alone for their weathertightness.
  • They obstruct the rainwater runoff if they block more than 50% of the pan.
  • The E.P.D.M. flashing is flexible and requires structural support for the pipe.
  • Their longevity is jeopardised if they are distorted or under stress.

To overcome some of these disadvantages, follow these directions.

  • The square base should be turned at 45° to the fall of the roof cladding. This will minimise the obstruction, and dirt and debris are more likely to be washed away. See 8.4B Larger Vent Pipe Flashing and 8.4C Prefered Flashing Design for Larger Vent Pipes
  • All surfaces should be cleaned, and sealant should be placed around the flange base of the flashing before it is placed in position.
  • All surplus sealant should be removed.
  • The penetration hole in the roof cladding should be made through the rib, and the hole should be cut close to a purlin.
  • Only one rib of a profile should be cut out, as any further cutting severely depreciates the performance of the cladding. If more than one rib has to be cut, additional structural support is required and an alternative penetration design should be used. See 8.4C Prefered Flashing Design for Larger Vent Pipes.

Because of the disadvantages these flashings offer, they should be avoided in certain situations.

  • Never use this on a side lap.
  • This type of flashing is unacceptable on asymmetrical trapezoidal profiles if the size of the pipe and flashing restrict or obstruct the passage of water to less than half of the normal draining area.
  • This type of flashing is unacceptable on symmetrical trapezoidal and corrugated profiles if the size of the pipe and flashing obstruct the passage of water greater than one rib.
  • E.P.D.M. flashings should not be used for single flues, and for high temperatures, 60° - 200° HT silicone flashings should be used.
Other tray type proprietary EPDM flashings are available to suit larger pipes or custom-made flashings and can be used as shown and described below.

 

8.4A Small Vent Pipe Flashing

Small vent pipes can be installed using a hole cout through the rib close to a purlin, using a propietary Flashing placed at 45°.

 

8.4B Larger Vent Pipe Flashing

Bigger vent pipes that would obstruct more than 50% of the available pan width can be used up to 300 mm in width.
If more than one rib has to be cut, additional structural support is required and an alternative penetration design has to be used.

N.B. This penetration design can be used down to the minimum pitch of the roof cladding.

8.4C Prefered Flashing Design for Larger Vent Pipes

A large proprietary 250 mm diameter EPDM flashing, which would obstruct drainage from the catchment above. It has been designed with a self-cleaning 45° diverter flashing, while still providing the flexibility offered by this proprietary flashing.

8.4D Alternative: Large Vent Pipe Flashing

A Square fixed over fitted boot flashings can be used to a minimum pitch of 10°.

 

 

8.4.1 Plant Room And Conduit Penetrations 

Where flexible power conduits or telecommunication cables are required to penetrate the roof cladding, accessibility can be improved by using P.V.C pipe fittings and an E.P.D.M. flashing to weather a number of conduits.

8.4.1A PVC and E.P.D.M Flashing

This flashing should be fixed next to the purlin for support.

 

Safety bollards for fall arrest anchorages are required where regular maintenance is required, and these can be weathered by E.P.D.M. flashings.

Where plant room supports are required to penetrate the roof cladding, the designer should provide the support framing from Circular Hollow Sections (CHS) in preference to Rectangular Hollow Sections (RHS) or other hot rolled steel sections, because it is easy to flash the CRS with E.P.D.M. flashings. This procedure allows the E.P.D.M. flashings to be slid over the pipe framing during erection, and avoid the necessity of using retrofitting types.

The support framing should be in place, but below the top of the purlin, before installing the roof cladding. That allows the cladding installation to proceed without having to weatherproof multiple penetrations at the same time.

Proprietary support systems are available for lightweight support through to the purlins.

These types of supports provide clearance for cleaning but should not create an unwashed area underneath them.