Question about flashing

[Yokosukadweller]

Hello, I am new here. I am basically joining in search of information for my small studio project here in Japan.
I would like to ask your opinion / advice on the following.

I am putting roofing on my little studio that I am building. This is all DIY and I am just a weekend warrior.




The studio will have a wood fired oven, and so I need to run a double walled chimney through the roof. s

I got this type of flashing:

My roofing is stone coated steel sheets. I think that is the tricky part.
It's a steel roof but acts more like a shingle roof with the grainy top surface.

Here is my situation, showing the chimney hole and its position in relation to the roofing sheets.



My question is: with this kind of roof shall I adhere to the normal approach of keeping the bottom of the flashing on top of the roofing, and the top half of the flashing under the roofing? Or should I try to put the entire flashing under the roofing and just caulk around the hole? Has anyone here experience with this type of roofing, any advice would be very helpful and help avoid another too long analysis paralysis situation.

Cheers,

Simon

 

[stoveliker]

I see no good reason to deviate from the normal approach?

 

[FramerJ]

Standard installation- flashing goes over bottom piece of roof tile, under top piece. Caulk will fail in time.

 

[stoveliker]

What is the ID of that flashing? Does it fit with chimney pipe (class A) rather than stove pipe?

I.e. what is the rest of your flue system composed of?

 

[Yokosukadweller]

Thank you for confirming that my intended approach (above below piece/below above piece) is right. Someone somewhere else commented that maybe I could cut the matching hole in below and above pieces and simply put the entire flashing entirely below the roofing plates. I thought if executed well, that could look good and only require caulsking and flashing tape around the seams of that hole.

But now I think it is really the only good option to route the flashing out on TOP of the below piece, so that any water that might come in will flow back out on the roof.

Stoveliker- the flashing is 8" hole. It matches the chimney system I have which is a Seklirk shure temp 6 inch double wall system. You're thinking the boot/flashing doesn't match? I have tested it and it fits, it may have a quarter inch too large diameter hole, but I am hoping some silicon caulking and a stormcollar will work alright there.

 

[Yokosukadweller]

By the way, the flashing has three screw holes that would be on the lower edge of the flashing and would be exposed. Do you recommend I use those to fasten screws through the roof, or better avoid? I mean holes are a potential leakage, so if I can avoid screwing through the roof, I would...

 

[stoveliker]

I thought the flashing looked small (and was afraid you'd be sticking stove pipe thru it). Seems like you are doing things right.

Yes I'd put screws on the bottom holes. And put caulk (flashing cement, something specific for roofing applications) on top. Opinions may differ though. For me the risk of it catching wind is too much to not screw it down.

 

[Highbeam]

I avoid exposed fasteners whenever possible so would not use those screw holes because caulk fails and then you have a leak. With your big roofing panels though, you might not have a choice.

 

[begreen]

Yes, use screws on the bottom holes. The penetration of that size screw is minimal. It's a little messy, but if you put a dab of a good qualtiy silicone on the hole and screw through it, that will seal the hole for longer than we are around.

 

[Hogwildz]

Urethane caulk with hold better & last longer than silicone. You also have the option of making 3 cleats that you could slide the bottom edge of the flashing into, eliminating the need for surface screwing. The use screws as normal on area under the course of shingles over the upper flashing.

 

[Yokosukadweller]

Hello gentlemen - thank you for your inputs. I think there are pros and cons to using those screws, as we see from your advice.

For the moment I selected not to drill through those screw holes. I just put some roof caulking. Then there are 5 screws holding the flashing boot down to the roof, those 5 screws are all under the roofing. I felt more comfortable that way. We have a rainstorm coming mid next week, that will be a test to see.

I am just copying some photos to show the approach used. Now the chimney sits fine and dandy. I have to admit I am kinda proud it worked out and looks alright. I still have some heavy duty flashing material. I don't know the name of it, but it is real heavy and has a sticky side. I plan to put that on the upper part, where roof panel meets flashing. Just have to find a tutorial to see how to stick rectangular flashing material to a rounded surface without having all sorts of folds and mess-ups.

The chimney stands 92cm proud of the roof - that is just about 3 feet. I do not have support brackets on there. We do have some intense storms in spring and summer. I am not sure I need the supports, and I think I am still below the local code requirements for supports. I will confirm that and add them if that's better.

Thank you again!

Simon

 

[stoveliker]

Looks nice.
I have never caulked the.bottom edge of such flashing; I always figured it would be good if whatever gets under there can flow out from under the bottom.

 

[Highbeam]

Looks nice.
I have never caulked the.bottom edge of such flashing; I always figured it would be good if whatever gets under there can flow out from under the bottom.

I don’t like to use caulk/goop on it at all except on the actual storm collar.

 

[begreen]

Hello gentlemen - thank you for your inputs. I think there are pros and cons to using those screws, as we see from your advice.

For the moment I selected not to drill through those screw holes. I just put some roof caulking. Then there are 5 screws holding the flashing boot down to the roof, those 5 screws are all under the roofing. I felt more comfortable that way. We have a rainstorm coming mid next week, that will be a test to see.

I am just copying some photos to show the approach used. Now the chimney sits fine and dandy. I have to admit I am kinda proud it worked out and looks alright. I still have some heavy duty flashing material. I don't know the name of it, but it is real heavy and has a sticky side. I plan to put that on the upper part, where roof panel meets flashing. Just have to find a tutorial to see how to stick rectangular flashing material to a rounded surface without having all sorts of folds and mess-ups.

The chimney stands 92cm proud of the roof - that is just about 3 feet. I do not have support brackets on there. We do have some intense storms in spring and summer. I am not sure I need the supports, and I think I am still below the local code requirements for supports. I will confirm that and add them if that's better.

Thank you again!

Simon

View attachment 291614View attachment 291617View attachment 291618View attachment 291619 View attachment 291615

I like that style metal roofing better than what is standard here in the states.

A roof brace is installed at 5 ft above the roof penetration. This does not need it, unless more height is needed to meet the 10-3-2 rule.



Also, what stove is going to be connected to this chimney system? Some stoves need 15+ ft total flue system height for proper draft.

 

[Yokosukadweller]

I like that style metal roofing better than what is standard here in the states.

A roof brace is installed at 5 ft above the roof penetration. This does not need it, unless more height is needed to meet the 10-3-2 rule.

View attachment 291642

Also, what stove is going to be connected to this chimney system? Some stoves need 15+ ft total flue system height for proper draft.

This roofing might not be the prettiest, but I got it cheap from a surplus I I kinda like it the way it is. Also it is much lighter than shingles or other roof systems. So that is good in case of earthquakes, to try to make it less top heavy.

About the chimney installation: I realised that it was wrong to caulk the bottom of the flashing, so cut some slits to allow exit point for any water. Then I put sponge packing (?) around the top between roofing plate and flashing to close off the gap, and then put some heavy duty wakaflex around the top side. It seems pretty solid for now, but not sure how this will hold up to sun and weather over time. We will see.



The chimney in my case is almost precisely like the one to the right in your image example, so it looks like I am okay per code, but maybe I will install braces to avoid storm damage. The chimney in total is around 9-10 feet, you can see it connects to a wood fired (pizza) -another project, and it draws very well.

 

[begreen]

If it stays that height then no need to brace. That's a pretty cool pizza hut.

 

[Hogwildz]

You should have installed the neoprene flashing direct to the pipe's roof flashing, then installed the upper section of shingle over it, may be ok as is, as long and it doesn't pull away from the granulars on the shingle. Make sure you seal the storm collar all the way around, or it will leak down around the piping into the house.

 

[Yokosukadweller]

You should have installed the neoprene flashing direct to the pipe's roof flashing, then installed the upper section of shingle over it, may be ok as is, as long and it doesn't pull away from the granulars on the shingle. Make sure you seal the storm collar all the way around, or it will leak down around the piping into the house.

I agree the neoprene flashing on the granular of the roof is not the best match. If it pulls away too much I will replace it with a metal sealant, but for now it should be okay. I disagree on installing the neoprene directly onto the flashing boot and then rooing over it, since the steel flashing boot itself is quite large so it would then just be sticking on top of the steel flashing (the flat bit). So I don't think that would have made a difference. Again, the cleanest look would have been to forego the neoprene and just find a strong rubber type of metal sealant. I do not have access to such at the moment.