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General Plumbing and Gasfitting Talk => Plumbing => Topic started by: roberto on July 01, 2013, 07:45:13 PM

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Title: vent holes in roof
Post by: roberto on July 01, 2013, 07:45:13 PM
how do you mark a hole in roofing for a vent when going through the sifit?

any ideas???
Title: Re: vent holes in roof
Post by: robbo on July 01, 2013, 08:58:55 PM
hi roberto, i used to use a long pointed metal rod,cheers
Title: Re: vent holes in roof
Post by: roberto on July 01, 2013, 09:29:01 PM
how do u stop that sliding up the inside of the iron? do u have a small level on it and try and hold it in the middle of the hole in the sifit???
Title: Re: vent holes in roof
Post by: robbo on July 01, 2013, 10:15:21 PM
hi roberto,yeah it`s a bit of a guess but a sharp point on a 5/6mm rod and a smack with the hammer will normally do it, once yo have the approx position you can adjust as you cut the hole from above,always worked for me,cheers
Title: Re: vent holes in roof
Post by: anthonyc12 on August 02, 2013, 03:29:07 PM
hey robo by the way nice idea, why i did not think of that. i am facing same problem as roberto. i will try this and update my experience here. thank you
Title: Re: vent holes in roof
Post by: Rodza1 on August 11, 2013, 01:31:47 PM
I've done the same thing for a lot of years myself, metal rod with a decent steel point which you strike with a hammer or such to get a decent reference point on the roof as something to start with. Once you've made a mark,Cut a 20mm hole in roof so you can see down through it then push an offcut of pipe if you have one, up through the soffit hole youv'e already made and wedge it in place. It will show you if you are off centre or not with your initial mark by 10 or so mm, maybe a tad more.

If you do it this way you are almost guaranteed to cut a nice tight hole every time.Works pretty well. Ive done a few where my initial mark is bang on. I think after you've done enough of them you can trust your mark made with the pointed metal rod is really close so never mind checking with a offcut piece of pipe etc. Having the pointed metal rod vertically level and centered with the soffit hole when you make your mark/dent on the roof helps a great deal in being close to centre when cutting the hole in the roofing material for the pipe to pass through.
Title: Re: vent holes in roof
Post by: Badger on August 11, 2013, 04:03:59 PM
Laser level is the best I have found, just follow the red dots...real handy, centre every-time. 8)
Title: Re: vent holes in roof
Post by: Mylesgiraldo on April 09, 2015, 06:52:10 PM
If you cut the vent pipe at the same angle as the pitch of the roof, roof angle, you will end up with an elliptical shape on the end of your pipe. This shape can be used as a stencil to cut the exact shape in the roof sheathing required for the vent pipe to be true and plumb. The hole cut is usually an oblong circle shape, elliptical.
Title: Re: vent holes in roof
Post by: melving.crane on March 22, 2016, 10:07:18 PM
Hey Roberto, I use pencil to mark the place where I'm about to make a hole. Also use a reciprocating saw to cut away the area.
Title: Re: vent holes in roof
Post by: Enn on March 24, 2016, 08:33:51 PM
hey badger how about a .22 with good aim!
 but seriously I use an old motor cycle rear axle that has been sharpened to a point  and thinned down for about a quarter of its length aim for centre and perpendicular and give a good wack and viola straight through the iron!
( just a metal rod but thick and has a good striking surface) I have had good results with this method.
Title: Re: vent holes in roof
Post by: Badger on March 25, 2016, 09:04:38 AM
Enn....a.22 too small...... my 30 30 would be more effective right size hole too ;)

Melvin a tip for you (which you might already know)......if you use a reciprocating saw, or any other method that leaves metal shavings/pieces on the roof (which if you go back some years later you'll see causes rusting)......get a cloth and wrap it around a magnet.....it'll pick up all the shavings and when you get to the bin, pull the cloth off and all the metal pieces go with it.
Title: Re: vent holes in roof
Post by: robbo on March 25, 2016, 10:14:45 AM
hi guys...Excuse me sir you do realise that you are not allowed to discharge a firearm within 50mtrs of a residential area, cheers
..p.s. perhaps we should have a section on `Tips and Tricks` to make our work easier.
Title: Re: vent holes in roof
Post by: Badger on March 25, 2016, 09:40:11 PM
Yes Robbo mate great Idea, spread the experience and built up knowledge ..... tell "Plumber" to add it to the site, brilliant idea mate.



Title: Re: vent holes in roof
Post by: robbo on March 29, 2016, 10:15:31 AM
hi guys, hey Badger i think i should `Ask` Plumber to add a tips& tricks rather than tell him or he may dig his toes in, you know what plumbers are like,, Ha-Ha, cheers and have a good one
Title: Re: vent holes in roof
Post by: Badger on March 29, 2016, 05:14:53 PM
Totally true mate, sorry Plumber..... ;D


I should have said ask....story of my life being misunderstood, lol.