CHIMNEY VENT

[Dave123456789]

Hi I got my gas supply cut off my a professional and then boxed in the sky box etc last year

My chimney was swept and capped off at the top a few years before

My question is do I need a bottom vent too? And if so where?

I haven't noticed anyyhing but it's only been 1 year and I want to ensure the chimney can "breathe" as they say

Pls can you help

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[KenGMac]

Dave123456789, Hi

The accepted thoughts are that an un-used chimney flue can given certain conditions allow condensation to gather in what is an un-vented space.

This condition is called intersticial condensation.

The above does occur in flues that are not vented within the room by means of a vent cut into the chimney flue and importantly a capped but ventilated cap placed on to the top of the chimney pot.

if the chimney vented cap is omitted then rain can get into the chimney flue, when it does, the rain entering the flue will mix with the soot on the inner surfaces of the flue. This soot contains Sulphur which is a natural product of combustion

The mix of rain water, or condensation, causes the sulphur in the soot to form a weak Sulphuric Acid, this acid will corrode severely old lime mortar, to the extent that an exposed Chimney can disintegrate!

The most common effect of Sulphur attack are externally, discolouration of stone or brick, internally dark brown patches appearing on internal plaster.

The dark patches internally smell fairly strongly of tar.

Your problem is difficult to call, It could be that your property will not be affected, but?

Ken.

 

[Dave123456789]

Gym the bedroom above this room also has a chimney - no vent plate/guard thing

 

[Dave123456789]

Hi thanks

Would you just make a hole and put a vent plate thing to be safe?

http://www.screwfix.com/p/map-vent-gas-louvre-vent-white-76-x-229mm/4548d

Perhaps behind me tv so it doesn't show?

 

[Dave123456789]

I've just taken a pic of my chimney

It seems only one chimney has the vent thing cover? :-s

Other than the one with tv hung on All my chimneys are no longer in use no fireplace plaster boarded up no vent plates

BUT I don't see any dis colouring or anything on any chimney??

Untitled

• Dave123456789
• 30 Nov 2014
• 1

 

[KenGMac]

Dave123456789, good evening.

interesting history on this chimney?

If you look at your neighbour's side, you can see that historically someone has applied a coat of smooth cement render, seen between the two brick features, you side does not have this, it begs the question has your neighbour had problems?

if you copy and enhance the photo, I think I can see one chimney cowl the bit above one of the chimneys, but on at least two other chimney pots there appears to be some sort of a seal apparently held on by screw fixings? but possible UN-Vented? whereas the Cowl has a ventilation feature.

Again on an enhanced Photo you can see a thin layer of what could be a mortar or cement or Concrete? this could indicate that the top surface of the chimney head is or was suspect at one time.

But we are getting ahead of ourselves. at present, here is no internal damage, no dark stains, no smell of soot / tar?

By all means, insert Flue vents as a precautionary measure, at the same time I am deeply suspicious of the two pots with the flat possibly UN Vented caps? possibly others on the board can shed some light on what they may be? or indeed what they are called?

There is an old adage if it isn't broke don't spend cast fixing it.

ken

 

[Dave123456789]

hi i am not sure about the neighbor sorry as they are new.

what i also dont get is i have 3 chimneys in my house

the through lounge has 2 - and they run up to 2 more in the respective bedrooms above.

and 1 in the dining room - that runs up to the 3rd and final bedroom.

so why do i have 4 pots????

 

[ree]

Each fire opening has one single flue that runs up to terminate in a pot on the chimney stack.
Flues are never shared.
Chimney breasts might have two or more separate flues divided by brick "feathers".

The Blank Stoppers are caps inserted in the pots. This is bad practice unless an air brick has been inserted in the side of the stack. The flue needs to be vented at its top & bottom. The second pot has a Colt insert vent.

The top surface of the stack is flaunched. The flaunching sand and cement holds the pots in position.

Given that the neighbour's half of the stack appears to lack flaunching, or visible pots or terminals of some kind, it would be possible for water to enter on their side and penetrate to your side of the stack.