Chimney Pots and Cowls

[cwhaley]

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[stuart45]

When the rain hits the flaunching, there will be a certain amount of rain bounce, some of which will get into the flue. Some will also pool slightly and run into it.
It won't be a massive amount, and as with an open chimney pot, when the flues were brickwork and parged a small amount of water would be soaked into the parging and easily dry out.
However, once a stainless steel liner is in the flue, a small amount of water will run down into the appliance. This can damage the appliance over time, so ideally you try and keep as much water out as possible.
What you've got would be better sitting on top of a chimney pot.

 

[Koolpc]

Again, happy to be schooled but how so? As in - how would the water track into the cowl?

If mine let in the Niagra Falls, the open pots to the right must let in the Pacific Ocean.

The gap on the sides is gigantic!!!!!!!!

 

[cwhaley]

When the rain hits the flaunching, there will be a certain amount of rain bounce, some of which will get into the flue. Some will also pool slightly and run into it.
It won't be a massive amount, and as with an open chimney pot, when the flues were brickwork and parged a small amount of water would be soaked into the parging and easily dry out.
However, once a stainless steel liner is in the flue, a small amount of water will run down into the appliance. This can damage the appliance over time, so ideally you try and keep as much water out as possible.
What you've got would be better sitting on top of a chimney pot.

Thanks Stuart, appreciate the detailed reply.

Two flues as you can see. The one closest in the picture doesn't serve an appliance and has no liner. It serves an open and unused bedroom fireplace. I had the cowl put on to allow that flue to breath.

The liner is in the rearmost flue in my picture. If you look you can see it rising above the level of the flaunching so it's well protected from driving rain or pooling water. It's open end actually sits about 2" underneath the hood on the cowl.

 

[cwhaley]

The gap on the sides is gigantic!!!!!!!!

Absolutely, but that gap sits sideways on. The open pots sit facing the sky like an open bucket.

My cowls have a large overhanging hood and the flaunching slopes away from them.

I figured this must be enough to keep most of the rain out, but I'm not confident enough to say for sure hence starting this thread to see what others thought.

 

[Koolpc]

Absolutely, but that gap sits sideways on. The open pots sit facing the sky like an open bucket.

My cowls have a large overhanging hood and the flaunching slopes away from them.

I figured this must be enough to keep most of the rain out, but I'm not confident enough to say for sure hence starting this thread to see what others thought.

Well, i would be wanting them changed if it were me....

 

[aveatry]

When the rain hits the flaunching, there will be a certain amount of rain bounce, some of which will get into the flue. Some will also pool slightly and run into it.
It won't be a massive amount, and as with an open chimney pot, when the flues were brickwork and parged a small amount of water would be soaked into the parging and easily dry out.
However, once a stainless steel liner is in the flue, a small amount of water will run down into the appliance. This can damage the appliance over time, so ideally you try and keep as much water out as possible.
What you've got would be better sitting on top of a chimney pot.

I agree with this assessment. Rain will get in as described. The flouncing is relatively flat and water will pool and it will get blown down, espicually on the side of the neighbours as that is higher and nowhere for collected water to go except down your flue. If it is to stay like that then possibly add something around the base up to the first 2 mesh holes. 1.5 inch strip of stainless steel bent to a square riveted in place, sealed with lead mastic at the bottom - but that is a bodge fix for something that should of been done better from the start.

 

[Gasguru]

Normally any flue work either remedial or new is notifiable work to the local authority under the building regs.
You must be either Gas-Safe or Hetas registered to self certify your work.
A roofer (or builder) will not have the knowledge or qualifications to do so...and the qualifty of the work shown is evidence of that.
Over the years I have encountered many situations like this that have left the occupants in serious danger (some flues have completely failed to draw through badly installed liners). You should note that all solid fuel and decorative gas fire burn with very high levels of carbon monoxide, cooker and boilers are much much safer.

Those bird guards are designed to fit onto a square section chimney pot. They are normally available in different mesh sizes depending on whether it's serving a gas or solid fuel appliance (the regs specify the size). The suggestion of covering up the lower holes is totally irresponsible.
For a disused flue you would install a rain cap onto the chimney pot - they almost close of the terminal allowing a little air circulation up the flue to ward off damp.

The rear flue liner appears to be sitting at a height that may well obstruct the combustion products. Is it the correct diameter for its use? Have suitable clamps and plates been used to secure it etc. Was the existing flue thouroughly cleaned/swept?
As for the flaunching I normally use a 50/50 building sand/sharp sand at 3:1 with SBR/water to waterproof the capping. Use broken tiles to build up the thickness.

All new liners must have a data plate fitted in the property giving details of the liner manufacturer, it's suitable use, compliance etc.
There are multiple standards regarding flues.... Document J, BS 5440, BS715 etc. detailing the requirements.
I suggest you find someone suitably qualified to check/redo the installation.

 

[aveatry]

Normally any flue work either remedial or new is notifiable work to the local authority under the building regs.
You must be either Gas-Safe or Hetas registered to self certify your work.
A roofer (or builder) will not have the knowledge or qualifications to do so...and the qualifty of the work shown is evidence of that.
Over the years I have encountered many situations like this that have left the occupants in serious danger (some flues have completely failed to draw through badly installed liners). You should note that all solid fuel and decorative gas fire burn with very high levels of carbon monoxide, cooker and boilers are much much safer.

Those bird guards are designed to fit onto a square section chimney pot. They are normally available in different mesh sizes depending on whether it's serving a gas or solid fuel appliance (the regs specify the size). The suggestion of covering up the lower holes is totally irresponsible.
For a disused flue you would install a rain cap onto the chimney pot - they almost close of the terminal allowing a little air circulation up the flue to ward off damp.

The rear flue liner appears to be sitting at a height that may well obstruct the combustion products. Is it the correct diameter for its use? Have suitable clamps and plates been used to secure it etc. Was the existing flue thouroughly cleaned/swept?
As for the flaunching I normally use a 50/50 building sand/sharp sand at 3:1 with SBR/water to waterproof the capping. Use broken tiles to build up the thickness.

All new liners must have a data plate fitted in the property giving details of the liner manufacturer, it's suitable use, compliance etc.
There are multiple standards regarding flues.... Document J, BS 5440, BS715 etc. detailing the requirements.
I suggest you find someone suitably qualified to check/redo the installation.

There you go a proper expert. By the way I did not realise the flu was active.

 

[catlad]

What you've got would be better sitting on top of a chimney pot.

Designed to sit on top of a pot, I'm not sure why you didn't reuse the original pots; they look okay.

 

[Deluks]

Designed to sit on top of a pot, I'm not sure why you didn't reuse the original pots; they look okay.

I'm wondering if the builder wrapped them in bubblewrap before placing them carefully in his van.

 

[cwhaley]

I'm wondering if the builder wrapped them in bubblewrap before placing them carefully in his van.

Haha wonder no more my friend, they're in my garden.


Update as of this morning. I'm requesting the pots be reinstated with the cowls fixed to the top. I had bought them specifically to fit these pots after all. I still don't know how much rain would actually end up down the chimney had I left the cowls in place as they are, but while the scaffolding is still up I can't sleep knowing the pots should really be back on.

Lots of input to my post which I really do appreciate as it takes time to write. It's important to note that I am only at the stage of installing the liners and cowls, so nothing else to comment on apart from that.

The stoves will be self-installs, just like the one I put in at my last house. I sought and received building control approval on that and will be doing on these. Equipment was bought by me specially to work with the output of the stoves.

 

[aveatry]

I might be inclined to keep the ornate pots in my garden (or sell them ) and buy modern plain replacements for the roof.

 

[Gasguru]

What are building control charging you to get the install/flue work checked and signed off by a Hetas installer, although any installer is mad to sign off others work (when they can't really see properly whats been done), in the gas trade it's banned.
This could all come back when you sell the property....solicitors want all the paperwork in order.

 

[cwhaley]

What are building control charging you to get the install/flue work checked and signed off by a Hetas installer, although any installer is mad to sign off others work (when they can't really see properly whats been done), in the gas trade it's banned.
This could all come back when you sell the property....solicitors want all the paperwork in order.

£600. Everything I will do in this install (like the last install) will be by following the appliance's manufacturer's guidance and by following the latest revision of document J.

Energy security in this county has a very bleak future, so I'm doing what I can to try and mitigate against all the problems that will bring.

When I sold my last house in May 2024, the stove I'd installed there and ran for 7 years didn't even get mentioned. I did provide the twice yearly sweep certificates, which often involved smoke extraction tests and camera inspections. Should it have been brought up, I'd have just disconnected it. As it happens, there was a poor self install in one of the rooms here, which just exhausted gases into the open flue... They admitted to me what they'd done and it wasn't really an issue, they just took it out. Way bigger considerations.