Jump to content

Stove flashing


Recommended Posts

Is it typical to buy the upper part of the flue, stays and cowl when your fixing your roof or do you leave the stove till later in the build? Slating will occur in a few weeks and this is the last item that I'm yet to order.

 

Should I:

 

Leave all together till much later in the build?

Fit a flashing and leave a hole in the roof?

Fit a flashing and final flue so it looks like what is shown below

 

image.png.9c97c5ec31a6e409fe9a0577eae35322.png

 

I really like this the charnwood country 4, has anybody purchased this one?

 

https://www.charnwood.com/project/country-4/

 

It describes the flue as being a five inch flue outlet, so without sounding daft, I would need a 5 inch flashing?

 

Any comments would be greatly appreciated.

 

 

 

 

 

 

 

Edited by Thedreamer
Link to comment
Share on other sites

@Thedreamer

You could buy one of these lead flashings and get the roofers to fit it now. You'll need to check with the stove supplier to find out the diameter of the eventual stove pipe that they will be fitting so that you can correctly size the diameter of the lead flashing. The stove pipe will pass through it and they will install a weather skirt at the junction. The lead flashings are available in a variety of sizes. If you want a stove pipe without any bends it will also be important to very precise with the location of the lead flashing.

https://www.roofingsuperstore.co.uk/product/6-lead-roofing-slate-450mm-x-450mm-x-45-degree.html?gclid=CjwKCAjwwJrbBRAoEiwAGA1B_T59_q_aZ-zcEN0Q3W33OElZ6cpUSJqX5FjKsh3wwMYmFJIHcBsv3RoCpjcQAvD_BwE

For a 5" stove pipe you'll need a 6" flashing

Edited by Ian
  • Like 1
Link to comment
Share on other sites

No I don't think you use that sort of flashing with a twin wall flue pipe.  This is what you want https://www.flue-pipes.com/flashing-30-254.html

 

flue-pipes.com is where I got mine from, the cheapest I could find.

 

Depending how air tight and how well insulated you are building, you might want to look for a stove that takes it's combustion air direct from the outside via a duct rather than from the room. 

  • Like 1
Link to comment
Share on other sites

The guy who is currently doing my stove install came and put the bit through the roof in place 18 months ago, so the roofers could fit a lead flashing, and that's how it stayed until this weekend.

 

On the subject of airtightness though, I'm concerned I've made a massive oversight by installing a stove.  I got a room-sealed wood burner and put in an external air supply under the floor, but the installer is telling me that the penetrations between floors need to be ventilated (ground floor to first floor, first floor to loft).  This effectively gives me a ventilation shaft linking my warm, airtight ground floor to the open air....  

 

I naively didn't expect around the flue to be the leaky bit.  Surely there's a better solution than this?

  • Like 1
Link to comment
Share on other sites

  • 4 years later...
On 06/08/2018 at 18:35, Roundtuit said:

The guy who is currently doing my stove install came and put the bit through the roof in place 18 months ago, so the roofers could fit a lead flashing, and that's how it stayed until this weekend.

 

On the subject of airtightness though, I'm concerned I've made a massive oversight by installing a stove.  I got a room-sealed wood burner and put in an external air supply under the floor, but the installer is telling me that the penetrations between floors need to be ventilated (ground floor to first floor, first floor to loft).  This effectively gives me a ventilation shaft linking my warm, airtight ground floor to the open air....  

 

I naively didn't expect around the flue to be the leaky bit.  Surely there's a better solution than this?

 

 

You appear to have had the same concerns as me regarding the ventilated firestop and i was wondering if you came up with a solution.

I have a reasonably airtight newbuild with mvhr. Im installing a stove with external air source. The regulations state you must have a ventilated firestop between floors so i am basically connecting my living room directly to the cold attic space. 

Link to comment
Share on other sites

On 21/03/2023 at 22:11, Elton said:

i was wondering if you came up with a solution.

I did, but not an 'official' one.... where the flue exited the airtight layer into the loft space (first floor ceiling), I replaced the ventilated thing with cement board and sealed it with fireproof mastic.  I can't see as that's significantly different from, say, a twin wall flue exiting a vaulted ceiling tbh.  Between floors is boxed in and ventilated top and bottom.

  • Like 1
Link to comment
Share on other sites

I was thinking of doing something similar. As I understand it the purpose of the ventilated firestop is to stop the build up of hot air in the boxing. So if i block it at the vapor barrier  going into loft space but i put ventilation in the boxing below it should do the same job. Is this what you did? If so what size vents did you put in the boxing?

I does seem silly to me that there is no provision for air tightish houses in the regs

 

Link to comment
Share on other sites

  • 1 year later...

@Roundtuit @Elton Did you find a solution to maintaining the airtighness from ground floor and out of the cold loft?

 

I'm planning the same for an airtight house with MVHR, ground floor 5Kw stove, direct air intake, twin wall that passes through to the first floor bedroom, then through the airtight barrier of the first floor bedroom into the cold loft.

Link to comment
Share on other sites

As above: I used cement board at loft joist level (fixed to joists, with a hole cut in it for flue, assembled in two halves) sealed with fireproof mastic around the twin wall flue and across the joint, and then taped the airtight membrane to the cement board at a safe distance fron the flue.

  • Thanks 1
Link to comment
Share on other sites

On 05/08/2018 at 23:15, Thedreamer said:

Is it typical to buy the upper part of the flue, stays and cowl when your fixing your roof or do you leave the stove till later in the build? Slating will occur in a few weeks and this is the last item that I'm yet to order.

 

Should I:

 

Leave all together till much later in the build?

Fit a flashing and leave a hole in the roof?

Fit a flashing and final flue so it looks like what is shown below

 

image.png.9c97c5ec31a6e409fe9a0577eae35322.png

 

I really like this the charnwood country 4, has anybody purchased this one?

 

https://www.charnwood.com/project/country-4/

 

It describes the flue as being a five inch flue outlet, so without sounding daft, I would need a 5 inch flashing?

 

Any comments would be greatly appreciated.

 

 

 

 

 

 

 

We are currently planning to install a Charnwood Aire 3 with direct air kit.  To attempt to future proof I’m going to price up converting immediately above the fireplace to 6” twinwall insulated flue.  
 

The top section will go in as early as I can and before roofing as I want the roof on and scaffold down pronto. 

I will be doing the instal myself as I can under building regs, no need to pay for a Hetas dude.  
 

I talked through the instal with a technical guy from a local company that I’ll use for supply and I understood I have to ventilate each void, section by section.  But from what he described as long as I ventilated each section there is no need for sections to interconnect. 
 

So I’ll be putting a metal ceiling closure plate just below my cold loft, thus preserving my airtight layer. 
 

Unless of course, I’ve completely misunderstood!

 

Link to comment
Share on other sites

15 hours ago, Roundtuit said:

As above: I used cement board at loft joist level (fixed to joists, with a hole cut in it for flue, assembled in two halves) sealed with fireproof mastic around the twin wall flue and across the joint, and then taped the airtight membrane to the cement board at a safe distance fron the flue.

Great solution. Thanks.

Link to comment
Share on other sites

15 hours ago, Iceverge said:

You can get an airtight grommet to join to your airtightness layer. 

 

 image.jpeg.47e9f5a99cf10e752784a2e4572fcb95.jpeg

Thanks. I thought these were just for the external roof outlet but probably provides a better seal than a DIY job. At least theres a way forward with it. Do you have a name for this so i can check if they do a 200mm I.D for the twin wall.

Link to comment
Share on other sites

@G and J You need to have the twin wall boxed in after it leaves the room with the burner in, and in a cold loft it requires boxing or a cage around it so i believe. For future proofing leave at least 70mm clearance between the twin wall and combustibles and ensure the twin wall starts lower than 450mm from the ground floor ceiling if using single wall before it. Make sure there's no more than 4 bends or offsets in the complete flue.

 

I priced building control to sign mine off at £300 but they were really trying to put me off explaining theres an 8 month waiting list due to only 2 inspectors for a large area. 

Link to comment
Share on other sites

59 minutes ago, ruggers said:

You need to have the twin wall boxed in after it leaves the room with the burner in,

Is that a new requirement?  My twin wall is visible passing through the bedroom above and BC who signed it off were happy with that.

Link to comment
Share on other sites

1 hour ago, ruggers said:

Thanks. I thought these were just for the external roof outlet but probably provides a better seal than a DIY job. At least theres a way forward with it. Do you have a name for this so i can check if they do a 200mm I.D for the twin wall.

 

Try googling something like "twin wall flue grommet".

  • Like 1
Link to comment
Share on other sites

Link to comment
Share on other sites

1 hour ago, ProDave said:

Is that a new requirement?  My twin wall is visible passing through the bedroom above and BC who signed it off were happy with that.

It's one of those case by case, area by area things I think. I don't think it's a strict rule, but B.C seem to like it boxed in to prevent fire spread from floor to floor through the vented plates or people resting things against it. 

Link to comment
Share on other sites

1 hour ago, ProDave said:

Is that a new requirement?  My twin wall is visible passing through the bedroom above and BC who signed it off were happy with that.

Don't think there's any requirement to box in, just need to maintain distance to combustibles. I think you can get the aesthetics for the firestop and vent like so image.png.8c94a97164242c12bf305ce8199cf540.png

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
×
×
  • Create New...