capping chimneys (bump)

[mary]

just a thought about my last post.

I cap my disused chimneys with lead (actually they already are) but sort of squeeze in a length of rigid hosepipe (a bit like Elvis used to do) and sort of *clingfilm* it in with the lead which is fairly malleable as well as being unlkely to blow off -would that provide enough ventilation? One end of the hosepipe (about 1 foot in length would be in the chimney pot and the other would be on the outside of the pot .

[Tim S]

mary coughed up some electrons that declared:

If I cap my disused chimneys with lead (actually they already are) but

I don't think 1/2" hosepipe is really enough.

2" waste pipe or pond hose might be better, but I feel even that is borderline.

Cheers

Tim

[neverwas]

Agreed. A typical flue vent has 10+ holes each around 25mm diameter. See eg

2" waste pipe or pond hose might be better, but I feel even that is > borderline.

I'm a numpty on chimneys (and most everything else) but, having "been here" lately, wonder if a 2" pipe might look like nesting heaven to a range of local wildlife?

If there are lead cappings in place, and they have been there some time without blowing away, do they already provide some ventilation simply by not sitting flat all the way around?

One way to check that might be to check the draught from the fireplaces. But I'll not recommend a smoke tablet to test that (especially not if you have guests in the house).

PS Are the photos here

right? So we are talking not about 5 or 6 flues but 5 or 6 *stacks* ?

[Andrew Gabriel]

> If I cap my disused chimneys with lead (actually they already are) but

As I mentioned in the earlier thread, I cut a half-brick sized vent at the top. I was concerned that might be too small, but it seems to be OK. Wouldn't want to go much smaller though. Didn't go any larger incase it affected stability of the chimney. Bottom vent is a full brick (to the outdoors).

[mary]

yes those are the right photos,There are 5 pots sticking out of the top of the far right ^stack* I think there are 3 stacks (not quite sure what stack means...)There are 2 white marks on the left of photo that look like chimney stacks but are just paint or reflections One stack has 5 pots ,another has 3 and another has 2.. On the largest stack with 5 potsthe farthest pot has been cemented (I am afraid to go near it as it is a bit precipitous) and 2 of the others serve 2 downstairs rooms. So 2 others are a mystery as there are only 2 bedrooms they might have served and it seems too big a job to investigate where all the firerplaces were in the past I might try and loosen some of the lead cappings and maybe raise them up a half inch with a bit of putty maybe (trim the overhang a bit also?) Hopefully the weight and aerodynamics of the lead caps would prevent them flying off in a storm . (I have emailed a few local chimney firms to see if they know where I can buy a commercial 13" cap but no reply as yet)

[neverwas]

Thanks for clarifying that.

Belated question. Is it definitely 13" *internal* diameter at the top of the pots?

[mary]

I am pretty sure it is 13" -but external (I didn't realise those measurements were normally internal) So without remeasuring I guess that would make it 12" internal.

[neverwas]

I don't know if there is a convention as such on that. From browsing a few catalogues last year, most modern pots seem to be classed by their use (solid fuel, 125mm flue, etc) and by their height.

But the catalogues do give both internal and external measurements. They suggest 13" external is possibly (very probably?) a lot less than

12" internal. Even the pots on our little Victorian terrace had walls over 1" thick. Modern pots (eg Red Bank) are often 2~3" smaller inside than out (more for some bigger pots).

So I thought it worth asking in case someone who really knows about this stuff can advise you better.

[mary]

just remeasured and is is 11" internal (still 13" external)

[Mark]

If I cap my disused chimneys with lead (actually they already are) but

I would suggest you would be better fitting elephants foot caps, they will keep the stack ventilated but keep birds and water out. If ever the need arises to open up the fireplace at a later date you only have to lift off the cap. They are listed as Flue Ventilator on this URL

much cheaper from a builders merchant :)

-

[neverwas]

I think that is too big for the run-of-the-mill spigot flue vents. But I recalled at least some manufacturers made bigger ones and found Red Bank list one with a 235mm spigot and 325mm overall width. See item 120 on

I can't tell from that if the holes would be covered by the pots or not. But a local supplier (or Hanson's own technical support) might be able to tell you. May not be cheap though (unless lots of pots are so big in Connemara).

[mary]

thanks for that.I think I will give a ring to the main hardware shops in Galway City ......

[Phil L]

If I cap my disused chimneys with lead (actually they already are) but

This is a waste of time and will look dreadful.

Remove all the lead and remove half a brick from opposite sides of the chimney. lay a flagstone or slate in cement over the perimeter of the brickwork. If you use slate, you will need to add somemore weight on top, two bricks with cement inbetween wil be heavy enough.