GARRDAL 2 piece flashing. When obstacles restrict using a one piece boot

GARRDAL 2 piece flashing. When obstacles restrict using a one piece boot

GARRDAL 2 piece flashing. When obstacles restrict using a one piece bootGARRDAL 2 piece flashing. When obstacles restrict using a one piece boot

Installation Instruction


Garrdal fits most pipe sizes and roof slopes

Until you have installed a few a check list is helpful. Keep in mind that some of the videos are for demonstration and may not show all the necessary steps for a proper installation.

1) Ice and water shield should be on the roof deck and shingles should be installed to the pipe that needs flashed.

2) Dry fit and trim the upper and lower parts of Garrdal 2 piece flashing. Remember that the "collar" of the lower piece needs trimmed so it allows the upper collar to seal around the pipe. 

This image shows IMPROPER TRIMMING. An untrimmed collar of the lower (eaves side) does not allow the upper Garrdal piece to properly seal against the pipe. 

3) Fasten the lower "half" first keeping the fasteners nearer the conical portion (inside). This will allow the upper portion fasteners to be located on the outer portion without worry of striking the already placed fasteners.

4) Dry fit the upper "half" of the flashing.

5) Apply sealant between the upper and lower "halves". This will deter bugs and driving rain. See FAQ for notes on approved sealants.

6) Fasten the upper half of the flashing.

7) Shingle as you would any other flashing. Seal assist where necessary. See FAQ for approved shingle trimming. 

The images below show a properly trimmed collar. Trimming from the outer edge of the rounded part of the collar parallel to the side of the Garrdal unit for the 3-4 inch rib or smaller, you are assured that the upper portion can press against the pipe. Trim larger ribs in a similar fashion, keeping the lower collar out of the way of the upper collar when you dry fit the upper. 


The collar or gasket of the lower, eaves side of the pipe Garrdal flashing needs trimmed not just in a circular fashion on the inside of the rib of the collar but also to prevent the remaining edges from "creeping" or climbing up the pipe and stopping the upper portion from pushing against the pipe. 

Note that many caulks and sealants have different characteristics. Some are meant for an outside bead to air cure and others are OK as a sealant between layers. Read the instructions of what you are using. Look for NP-1 on the label and most should be suitable. 

Recommended sealants based on adhesion, flexibility and compatibility  with Garrdal materials and asphalt shingles. 


NPC #900 Solar Seal

Geocel 4500

3M weatherstrip adhesive (EPDM) compatible.

Karnak-Flex, Rubberized Elastomeric Sealant.

Boss 125 multi-seal

Gardner Neoprene flashing cement

Alpha Sealants 1010 or 1021

Dicor 501 or 551

Henry 900

M1 by Chemlink


Safe on Garrdal materials but not on shingles.

Black Jack super flash cement.

NOTE- If it is not listed here do not use when installing Garrdal 2 piece pipe flashing. Email with your desired sealant and we will add it to approved sealants if we deem it compatible. 


Use this image as a template when replacing a fouled pipe flashing without having to remove the bad flashing or trying to match shingles. Right click and open the image in a new tab, set the printing preference to landscape so the sides of the template are 9 inches across.)

Trim the eaves side of the Garrdal flashing as usual and break the seal of the shingle on the high side of the pipe. Using the template provided, trim the shingle(s) on the high side of the pipe. Test that the high side of Garrdal can slide under the trimmed shingle The underlapping shingle may need trimmed as well or nail popped. Fasten the eaves side of Garrdal (over the bad boot) and slide the high side of the  Garrdal under the trimmed shingle. Seal between the gaskets and fasten the high side of Garrdal flashing to the roof. Seal assist where indicated and any manipulated shingles.


1) Dry fit the pipe flashing parts against the pipe to be flashed. Assure a snug fit. If ribs need to be removed to accommodate a larger pipe, carefully trim one rib at a time to the inside of the rib. 


2) The angle between the pipe and the roof is smaller (acute) above the pipe and larger (obtuse) below the pipe. This means that the flexible collar of the flashing will need dry fit and trimmed. Garrdal flashing parts are made with more collar than needed to allow for trimming of the open end of the collar that meets the pipe. 


3) Dry fit and trim either or both the top or bottom collar before seal assisting and fastening to assure a watertight seal. See the other images in the FAQ and gallery section. 


4) When dry-fitting, the top portion of the collar can be trimmed for neatness as well. 


5) If the hole needs to be larger, nick above rib (toward hole) and carefully tear or trim away flexible portion to seal around larger pipes. Hole will seal up to a 5 3/8 inch pipe. Trim the collar as shown above. 


6) Assure the collar presses firmly against the pipe and fasten lower portion of flashing to the roof. 


7) Dry fit upper portion same as lower. Apply bead of approved sealant to lower portion. 


8) Push flexible portion of upper Garrdal flashing against pipe and gently push down over lower portion, The top should nest over the bottom and sealant. Position fasteners where they will be covered by the shingles. 


9) Your 2 piece flashing is now the same as a 1 piece and shingling from the pipe and above can be done the same as around a one piece pipe boot. 

Hiding the seam with a compatible black caulk is allowable. 


 1 7/8 pipe on 5/12 pitch Garrdal lower install 

 1 7/8 pipe 5/12 pitch upper Garrdal install 

Installation of Garrdal 2 piece pipe flashing on 3 1/2 inch pipe. 5/12 pitch