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Frequently asked questions.


Does Garrdal need any trimming? Yes, the angle between the pipe and the roof deck is smaller on the peak side than the eaves side. This leaves parts of the lower flexible collar that need trimmed to allow the  upper piece to snuggly fit against the pipe.  Different slopes and pipe sizes will need different trims to neaten the upper part. There are some before and after images. There is a trimming guide for the eaves side GARRDAL section on the installation page. Optional trimming for the upper piece is dependent on the slope of the roof.


12/12 pitch 2 1/4 inch

When the lower Garrdal part is dryfit there is an edge of the collar that will foul the seal of the upper Garrdal piece so it should be trimmed.



Marked for trimming

After dryfitting the upper Garrdal piece the part of the lower Garrdal piece was marked for trimming.


Trimmed and ready

After the lower portion of the collar is trimmed, the upper part of the Garrdal collar can snuggly hug the pipe.



Untrimmed is a potential leak

Trimming allows the upper sleeve to hug the pipe.

Crisp installation of the lower (eaves side) Garrdal piece by Champion Roofing, Altoona PA.

Upper is installed and it is ready for shingles. 

Does Garrdal install easier on some slopes compared to others? Yes. The steeper the roof slope the greater the difference in the pipe to roof  above and below the pipe (12/12 roof is 45 degrees above the pipe and 135 degrees below) A 3/12 pitch roof is about 14 degrees so the angle between the pipe and the roof on the peak side is about 75 degrees and 105 degrees on the eaves side so it is faster to dry fit and prepare for installation. Note that the Garrdal pieces are already manufactured for a slope so these differences in angles are even less. The images below are of a 3 1/2 inch pipe on a 6/12 roof.


Does Garrdal install easier on larger or smaller pipes? Below is a 3 1/2 inch pipe on a 6/12 pitch. A larger pipe will have the pipe closer to the rigid part of the Garrdal flashing portions. The structural stability of the base makes Garrdal easy to install around all pipes but larger pipes tend to be a little easier to work with.

Does  the old electrical mast boot need to be removed? Normally we would say yes but...The rubber collar can aid in helping seat a Garrdal 2 piece flashing providing it can safely be removed from the metal portion. It can be a resting place for the lower portion of the Garrdal collar allowing the installer a more rigid base to apply pressure to when sealing the top and bottom collars. Alternatively it can be slid down to apply downward pressure when sealing the two pieces and if the condition warrants, the rubber collar of the old mast boot can be left there as an added protector.


Can the pipe be built up under the Garrdal collar? Yes, using a Garrdal flashing on a small pipe might leave a couple inches of flexible collar between the pipe and the rigid thermoplastic base of the Garrdal flashing. Securing a piece of EPDM or other method of creating a "shelf" under the flexible (like the rubber collar of the old mast flashing) can aid in sealing. Building up the pipe and sandwiching the sealed Garrdal collars with the old boot rubber can also work.


Should Ice and water shield be installed on the roof deck? Yes, recommended for most penetrations including Garrdal.


Where is the recommended shingle placement? Water should have a means of shedding off the roof and the installed accessories. Leaving a 1/4 to 1/2 inch space around the conical "riser" of Garrdal will allow for shedding onto the shingles.


Apart from sealing the collars of the top and bottom, should I seal anything else? Exposed fasteners should be sealed. We also recommend the horizontal hump on the upper portion that goes over the rigid lower portion get a dab of sealant or silicone to stop water from running sideways. Seal assisting is a good idea for most accessories or shingle manipulations. The hump is necessary so the pieces nest together. A dab on the hump (under the shingles) will prevent rain from running horizontally. Images below

The collars or made from a vulcanized TPE from Delta Polymers.
delta poly tpv.pdf
Adobe Acrobat document [49.9 KB]
The base fastened to the roof is made of Copylene.
Santoprene is the best known brand of the material used for the collars.
copylene santoprene.pdf
Adobe Acrobat document [282.2 KB]
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