Chimney Pointing/Flaunching

[cycloneuk]

I knew the 1 pot was leaning, but now have scaffold up and have been able to take a better look. I need to redo the flauncing and reset the pots, I did the other chimneys flaunching in 2/1/1 of sharp sand, builders sand and cement.

The top 3 exposed courses are going to likely need rebuilding on this, it looks like an engineering brick. Will a 4/1 mixed of sand/cement be ok or should I use something like this https://www.diy.com/departments/blue-circle-quality-assured-ready-mixed-mortar-20kg-bag/35726_BQ.prd thats got lime in it.

I was hoping to do this tomorrow and no where near me stocks lime.

 

[^woody^]

3:1 using sulphate resistant cement, not any old ready mix - which is for general building

 

[Dereekoo]

3:1 using sulphate resistant cement, not any old ready mix - which is for general building

I assume the pots don't belch out sulphurous smoke anymore so sulphate resisting cement a waste of time if indeed there was any need for it in the 1st place. 3:1 ordinary mortar (due to its exposed position) will more than likely see you off to your grave. Use plasticiser if you want a buttery mortar as with lime

 

[stuart45]

Sulphate attacks were quite common on chimney stack joints. This was a cause of the lean where the joints on one side expand more because of the direction of the driving rain.
Certain bricks contain sulphates as well.

 

[cycloneuk]

I used 4:1 with a bit of plasticiser, that was recommended on another forum. Nearly every single one of them exposed bricks I could wiggle and pluck out straight out. I think the flaunching had been done in the past, but somone had just gone over the top of lime by the looks of it, it was white and crumbly under it.

I haven't had time to get the pots on, I presume it will be ok for a few days even if it rains? as the flue holes are not much bigger than the top of the pots anyway.

 

[^woody^]

I assume the pots don't belch out sulphurous smoke anymore so sulphate resisting cement a waste of time if indeed there was any need for it in the 1st place.

Ther flue will, and the chemical will migrate through the stack

 

[Bouy]

Ther flue will, and the chemical will migrate through the stack

Their flue will what, belch out sulphurous smoke?

 

[^woody^]

Their flue will what, belch out sulphurous smoke?

Traditionally, a flue "belches" out flue gases, which may include smoke and may contain sulphur [dioxide].

It's equally traditional for past belching to have deposited the same chemicals into the flue structure.

 

[Bouy]

Traditionally, a flue "belches" out flue gases, which may include smoke and may contain sulphur [dioxide].

Natural gas mainly methane with a smattering of other ingredients including sulphur but not anywhere near like the quantities coal fires would produce.

It's equally traditional for past belching to have deposited the same chemicals into the flue structure.

But without the rain to make it into a sulphuric acid solution

 

[catlad]

I always add a waterproofer to the mix when I'm flaunching a chimney.
You could do with a few bits of broken slates to balance the pots on whilst you are casting the mortar. ( check the feathers are stable whilst you are at it )

 

[cycloneuk]

I need to get the pots back on and do the flaunching, how long will it take before it's safe if it rains? chance of scattered showers for next day or so but will be hit and miss.

 

[^woody^]

It depends how heavy the rain is