Chimney ventilation

[BinE]

Hi Folks,

I'm currently in the process of bricking up my fireplace and having the chimney stack removed down to roof level. The fireplace is built into a chimney that's situated on an external wall on the side of the house, as shown in the photo below.

Having read through many different historical posts where others have done the same, the general consensus appears to be to add an air brick at the bottom of the chimney and one at the top to provide air flow in a bid to mitigate the build up of moisture within.

I've noticed that there is already an air brick with some form of baffle/cover at the base of the chimney just below the damp proof course on the right hand side, as can be seen in the photo below.

The photo below is a close up of the air brick.

Having removed everything from the fireplace to expose the original chimney cavity, I can't see how air could flow from the external air brick into the chimney. The fireplace has no visible ventilation other than the flu above it. My question is whether anyone knows if the air from this external air brick is somehow joining into the flu within the chimney at a higher point where I'm unable to see it, or perhaps its allowing air into the chimney structure surrounding the flu within the chimney, or maybe it isn't related to the chimney at all?

This one has me scratching my head. Any help / insight would be very much appreciated!

As an aside, one idea that came to mind to test whether air is finding its way into the chimney would be to use a smoke pellet. If air is being drawn from the air brick into the chimney then in theory it should eventually escape through the top of the stack?

 

[JohnD]

You have to ventilate both flues top and bottom. When a chimney is being taken down I favour demolishing it below the roofline and leaving it open in the loft. Add a grille to prevent anything falling down it. Putting the roof over it removes the need for future leak and flashing maintenance.

Disused fireplaces can be repurposed ornamentally, or as cupboards or to hold concealed cabinets or wallsafes.

 

[BinE]

You have to ventilate both flues top and bottom. When a chimney is being taken down I favour demolishing it below the roofline and leaving it open in the loft. Add a grille to prevent anything falling down it. Putting the roof over it removes the need for future leak and flashing maintenance.

Disused fireplaces can be repurposed ornamentally, or as cupboards or to hold concealed cabinets or wallsafes.

Thanks JohnD, that's a great idea to go below the rough line and open up in the loft.

The repurposing aspect is also a good shout. However, the Mrs has other ideas. If I'm feeling brave I'll broach it again!

 

[Mrs Ten Names]

The external vent looks to be below DPC level.
Are your floors wooden floorboards on joists, sitting on the level of that DPC?
If so, my guess is that the vent is for underfloor ventilation. That would indicate it has no function as far as the chimney is concerned.

 

[Mrs Ten Names]

You've disclosed your email address with your most recent message. I suggest you correct that immediately.
If you have any problem doing that I suspect the mods will do it for you.

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