riv

I have just had a log burner stove installed in ( what was ) the open fireplace of my living room.
The metal pipe lining from the stove exits of course through the traditional chimney on the roof.

What I am starting to wonder is ~ what about the gaps between the round metal pipe, and the oblong chimney space ?

Is there not a danger of insects / bees / wasps / small birds / rats or whatever getting trapped in that gap ?

Is this me worrying about nothing or is it a known issue and something which needs a remedy like maybe concrete or other substance to block the gap at the top of the chimney ?
And how would that substance be affected by heat ?
Does that effect ( heat ) determine what the substance should be ?

pipe emerging at roof level ( before chimney put back in place

showing gaps between metal pipe and masonry

traditional chimney replaced over the metal piping


I am not in Portugal at the moment and have had these pics sent to me by the builder who did the work. It would need a lot of dictionary work to try to explain my worry. [ But maybe there's nothing to worry about ? ]

Pulaski

Short answer, yes, there is a real risk of problems. A neighbour has had several issues including what we think was a squirrel falling down the gap, with no way to get into the chimney/flue area above the firebox, but just enough cracks/gaps between the flue casing and the interior of the home to create an ungodly stink inside the home. The only solution was to pour mineral (clay, entirely non-combustible) cat litter down into the gap to mumify the corpse and absorb the stink.

​​​​​​​The preventative solution? A skirt around the flue, made from "hardware cloth" (the sort of heavy duty wire mesh that could be used for animal cages - smaller gaps, thicker wire, and more rigid than chicken wire), should eliminate most of the possible problems. That said, few dead insects that make their way in won't cause a significant issue.

riv

Thanks - but when you say ' a skirt round the flue' ~ you mean the last couple of inches of the flue pipe at the top where it enters the masonry chimney ?

As the whole thing is already in situ I don't see how one could stuff all the gap from top to bottom.

And I don't suppose you know how that stuff translates into Portuguese ?

BEVS

Your pics don't show the chimney and flue cap.

There should be one. What does it look like?

As Pulaski has written, there really should be a mesh and skirt capping .

Portugal has some very fancy old stone ones .What you need is a good stainless steel one.

riv

Well these are the pictures I have been sent.

As I understand it they indicate that the pipe comes up as far as the lower area of the masonry chimney at roof level ( you see a pic of its jagged edge, within the masonry chimney cavity ) and then the traditional chimney ( which had to be removed to allow the pipe to be pushed down the chimney to the stove below ) was replaced on top.

I think that what you see in the pics is all that there is ( as I said I am in UK so cannot take pics ).

Do you know what 'chimney and flue cap' would be in Portuguese ? But anyway, what exactly does that mean, as the chimney is a different thing from the flue ?

Pulaski

​​​​​​​Yes, a skirt would just be a ring of wire around the flue, to stop things, especially live things, from falling or crawling into the gap. Maybe "collar" would be a better word? But anyway I would take a piece of wire mesh about 12"/30cm wide and generously long enough to go all the way around (I would guess around 10-12 times the diameter of the flue) then wrap it around, bunching the top together and allowing the bottom to flare out. So long as the wire is stiff enough it should hold itself in place, but you could use a few self-tapping sheet metal screws to hold the wire in place so long as you don't pierce the roof. .... IMO 2-3 screws into the flue would be acceptable.

chawkins99

The last pic has the top cut off but it looks like the decorative holes are where the smoke/fumes would come out. Assuming there is a solid cap on top of that section, you only need to worry about 'critters' getting in through those holes.

Covering those holes with a small enough mesh should do the trick although may not look as pretty.

Pulaski

​​​​​​​I agree, I think I misunderstood the pictures, and hadn't realized that the masonry "chimney pot" had been reinstalled. ... I suspect that the chimney pot either blocked off those gaps, or the cement that holds it in place would have blocked the gaps.

BEVS

Ah! Get the sense of it now.
That is the decorative chimney capping being replaced. Odds are it also has a top.

Doubt there is much to be worried about in that case. It is traditionally what works in Portugal. If concerned perhaps some fine mesh around the holes would be the way to go.

Shanorme

As long as he caps it off there shouldn't be a problem.

riv

Thank you for these contributions / suggestions.

I have a feeling ( no more ) that nothing will have been placed around the metal flue to close the gap with the rectangular chimney cavity.

I wish to email the builder to ask him about this and wonder if any of you can suggest appropriate translations for 'wire mesh' and / or 'bridge the gap between the metal tubo and the masonry chimney cavity'.

I can write standard Portuguese but would welcome any help with these technical terms.

Shanorme

You don't need to bridge the gap. What is your concern about the gap?

riv

The concern is that if there is a gap between the circular metal piping and the quadrangular masonry surrounding it then into that gap could crawl any number of insects ( bees / wasps / cockroaches / flies / whatever ) or small animals ( birds / rats ) which would then cause any number of problems ( eg a wasp nest / or dying and causing disgusting odours )

That is the concern about the gap.

EMR

Any gaps should sealed and bird mesh installed over the vents,
We had the very distressing episode of at least one bird trapped in our chimney, the bird mesh had corroded allowing entry.
.I had to devise a way of removng their bodies, not a pleasant task..

Shanorme

Which is why several people have said that it needs to be capped off with a mesh skirt and any holes lined with mesh.