Flat Roof - Chimney Flashing Question

[Danno7]

6 in 12 for the roof pitch. Thanks again for the post, sincerely.

Dan

[Danno7]

Good point and thanks for the message. Here, if the structure is less than 10 x 10 x 8' high, which it is, it is up to the owner as to how it's built. Anything over that and the municipal by-laws kick in, the structure needs an inspection, etc. Having said that, even though it's not required, I'd still want to also make sure it's conforming to my local by-laws. There are a lot of buildings with flat roofs here, as well, but the more I researched , the more timid I got about flat roofs...Gulf's advice has been very sound and I was just curious what he might suggest . I'm definitely finishing it with a gable roof.

On another note, we had our first pizzas this evening! I used 2 rolls of ceramic fibre (4 layers in the dome and 3 on the sides) and it was barely warm to the touch only at the hottest spots! Very pleased and very thankful for this forum!

[UtahBeehiver]

You need to check your local requirements. Ontario is snow country so snow load and pitch are different than Gulf's area where wind load is more of a concern than snow.

[Danno7]

Hi Joe, thanks, you are the voice of reason! I am switching back to the first plan - gable roof! Question: what would you suggest for minimum roof pitch? I need to keep everything under 8'.

I've got some steel panels (see photo). I am just trying to figure out what to finish the walls with, to match (any suggestions, I'm all ears). Probably go with stucco. I am thinking that the steel would be the most Maintenance-free (it was pulled from an old barn). I will probably end up painting them, but there's nicer ones underneath.

Again, thanks sooooo much!!!

Dan

[Gulf]

I want it to last and be waterproof.

Dan,

I haven't seen much long term success with flat roofs. Even those with proven roofing materials. I'm not sure that flagstone is a viable opton for even a sloped roof, considering your region. Freeze/thaw will probably do a number on the joints. Is there any possibility of rethinking the flat roof design and opting for another choice of roofing material?

[Danno7]

Hey Joe, thanks for your message! This is the solid way to do it. I have a couple follow-up questions: The finished material on top will be random flag which is very uneven on its surface. Underneath will be a scratch coat at least 5/8" thick. Underneath the scratch coat will be the pond liner with molded rubber chimney flashing which I was going to put over the backer board (Densglass on roof and Durock for the chimney enclosure). I was also going to have the finished chimney enclosure flush with the front wall of the oven enclosure.

Should I still do a rigid flashing, or just rely on the pond liner/scratch coat/mortar? I am thinking the water will be pooling slightly because of the flat roof, and because the rigid flashing will only be on three sides (because the front chimney wall and front oven wall will be flush). I think I am probably missing something regarding finishing. I really appreciate your comments and advice, Joe. I am totally willing to go the extra mile on this because I want it to last and be waterproof. So, given that it will be random flag on top, and front of chimney will be flush with front wall of oven, what would you recommend? Thanks again!!!

Dan Lewczuk

[Gulf]

A metal bender can be easily made by clamping wood or metal at the exact spot of the bend. Sorry, I have no pics for this. HF has a very reasonably priced bender if you don't want to dyi. The bender can be used for the eaves drip and the metal taht conforms to the roof. The below pic shows the flashing as it conforms to the roof in my application. Since yours is a flat roof, it will look like this on all for sides.

That being said, many contractors nowadays will just butt the roof to the brick veneer and silicone the heck out of it without any flashing. That gets them past the 1 year call back for the insurance. I like permanent fixes myself. I hope that this helps. I may be able to elaborate if there are more questions.

[Gulf]

For your application, another bend in the eavesdrip flashing is needed to turn it vertical up the backer wall. You can rip and place scraps of 3-4" backer board on all four sides of your chimney. One run will work, but two layers may work better with the bead that is in most eaves drip. It doesn't matter if it is thicker than the veneer that you choose.

[Gulf]

Check back with the manufacturer of your liner for the recommended glue for seaming. Since it is a pvc product, I don't think that the temperature is as much of a concern as dampness and humidity. Even if temperature does figure into your product, you can maintain heat for the short times that pvc glues need to bond. Seaming the liner 360 degrees around your chimney is only a failsafe. That will be the last line of defense. You will still need to do a rigid flashing

To cap the flashing around a chimney, I always use "shingle eaves drip flashing". I embed this into the brick. It caps which ever custom made flashing that I use that conforms to the roofing material. I use a punch to make holes that will help it set firmly into the into the mortar. Placing the flashing over a wood board works for punching the holes fairly quickly. A drill would also work.

This is going to take couple or so posts due to pic size.

[Danno7]

Hello everyone. Much thanks to all the helpful answers on this forum! I could not have gotten to this point without you people!

I am now at the stage I will be cladding my frame work of my enclosure. I will have a flat 5' x 6' roof with a 6" 24" long ss duravent chimney. I will be enclosing the chimney also and covering with either brick or stone veneer. I've ordered a pond liner from HD for the roof.

Question I have is, what is the best way to weather proof around the chimney? I will have to cut the pond liner to accomodate the chimney. I can fold the membrane up the wall on one side of it but will need to figure out flashing for the other 2 sides (chimney will be flush with the front face). I will have some pond liner left over when I trim for the roof. Given the colder weather (hovering around freezing and getting colder), is there a product that will make a weatherproof seal if I overlap the membrane at the chimney, or should I wait until spring and use a pond seam kit? I looked at Blueskin WB tape, but since it is bitumin-based, it may not work with the pond liner which is flexible pvc. Any suggestions most welcome. Thank you!

Dan