Maybe this thread will help make some of you brave enough to cut a big old hole right into your roof. Venting air up high helps to keep the smell and noise away from those nosey folks that stop by.

This is in a shed,and will be used while I dry my plants,it uses a piece of Class B chimney flue pipe, so later on if I want to hook up a gas heater Ill be set to go. Class B is for gas appliances and is double wall, one section around 5 feet long is about 35 dollars, alot more than regular duct, but its required if I do hook a heater to it.

You need stronger pipe if you want to use a wood burner, if your positive it will only be used to vent the grow room, regular duct will work.

If possible if your doing this in a garage or shed, I would put the pipe at the far end of the building, when people look at it, that would be the "normal" spot for a chimney, who would have a heater right in the middle of a 2 car garage?

NOTE..you can use a flush mount attic vent,its the same process,but without the flue pipehere is a flush mount vent ,there are many kinds ,some have flappers to stop a back draft..MAKE SURE THE ONE YOU BUY AS A CONNECTION POINT FOR ADDING DUCT WORK

(PIC1 and 2)
First look outside and find the general area you want the pipe, then go inside and find your rafters, I drilled a hole dead center between my rafters, then pushed a wire up through the hole , this makes it easy to find your spot.

(PIC3)
Position the rain cap up or down so you dont have tiny pieces of shingles lift over when your done, youll see in pic 9 what i mean.


Either use a maker or just scrib around the inside the collar to mark you cutting area

(PIC1)
Its easier to start your cut if you drill a few holes for your saw blade to drop down into, i fine tooth blade cuts slower, but it will vibrate alot less than a rough cut wood blade, use a jig saw , or saws-all to make the hole.

(PIC2)
This is one of the tougher parts, using something thin, like a putty knife,break the seal on the shingles, you have to be able to slip the top half of the rain cap up under the shingles.


The nails or staples that are in the way,will have to be pried out, take your time so you dont tear a shingle, youll only have about 4 to 8 nails to remove.You need a flat pry bar to get this part done, sometime a piece of metal can be used to catch the nail head and you can hammer it out sideways.
(PIC3)
When you can slip the rain cap up under the shingles,its time to replace the nails under the shingles.

(PIC 1 and 2)
It may be easier to to slip a nail into place,and sit the flat bar on top of the nail, then hit the flat bar with a hammer to drive in the nails. Ill have a closer pic later to explain.


When you have the nails replaced you will have to cement the shingles back down, roofing tar ,some brands are called roof jack, can be bought for a chaulk gun, seal the nail heads and the edge of the shingle , stepping on the shingles will get them down flat again.

Slip the pipe up through the collar ,its usually alot easier to do from the bottom side,you may have to have someone hold the pipe,or have something to set under it.Double wall pipe has a arrow pointing up, on its side,this prevent gases from leaking out of the pipe.

When used for a heater you have to maintain a certain height above the roof .

ROOF PITCH - rise/run in inches

MINIMUM HEIGHT*

Flat to 7/12 - 1.0 foot above the roof surface

7/12 to 8/12 - 1.5 feet above the roof surface

8/12 to 9/12 - 2.0 feet above the roof surface

9/12 to 10/12 - 2.5 feet above the roof surface

10/12 to 11/12 - 3.25 feet above the roof surface


Chaulk around the cap, and then slip on a storm collar, chaulk around the pipe , where the collar will set,and slide the collar down into the chaulk, now chaulk the top side of the storm collar, the chaulk in the photo is white, but turns clear when it dries, buy a chualk with the highest rated temp rating you can find,or use flue sealer.

The top is covered with a vented cap to keep out rain and animals , I didnt show mine,no need to give people more to look for...( OG taught me that) only put screws in a double wall pipe at the very top,to hold the cap on.






Double wall classB pipe needs to be 1 inch from flamable material, they make straps to hold the flue, i made my own, i have a 1 inch piece of metal between the wood and flue, thats not shown in the photo.

Use a bubble level on your flue pipe so it straight up and down,befor installing your flue strap..

Heres the photo showing how I nail down a shingle without having to lift it up very high,old shingles will break, very old ones will just fall apart, to replace a broken shingle ,you just have to remove all of its nails and slide in a new shingle.

If your roof is very old, you may not want to try this, you will keep breaking more and more shingles as you try to replace them. If your shingles are that old,its about time for a new roof anyway.

Now you can add on the pipe of your choice, for use with a heater,you need more double wall pipe, if its just for grow room air,use the cheaper duct pipe to finish the connections.

Mine will be hooked to a carbon filter, its another DIY...

[NorCal]

ive always wondered about work like this but never seen it done, great article and the pix are nice, I never cared to attempt anything because of the risk of when it rains if the holes arent sealed properly it could be disastrous, thanx for the tutorial....

[Budweiser13]

Thanks man very helpful......

[Budweiser13]

OK mole what if the roof is concrete tile or that clay tile stuff can this still be done...