Fire flue pointing

[fernicarry]

As part of my ongoing pointing adventures, I've found a problem that I'm not sure how to tackle. Advice appreciated.

Pictures aren't great but basically after chipping away cement repairs I have a gap in the outer leaf all the way into the fire flues. This sort of straddles the two front flues, upstairs is capped off, but downstains still has a fireplace and I've verified that's where it goes by dropping a stone down...

How should I build this back up? Both of the big stones either side actually slope inwards so the gap is wider the deeper you go. There is the remains of the bit that divides the two flues just to the right of this opening which is quite poor too.

The downstairs fireplace won't be used without a liner. Do I need to worry about building up the masonry dividing the flues? If anything the gaps might be helping ventilate the upstairs flue.

Previously it was repaired by pushing chicken wire into the gap and then cementing over that. Would that be a good approach? With appropriate materials like stainless mesh and lime mortar of course.

Or should I dress those two big stones either side to get a straight edge and give me space to work, then build up the dividing wall back into the front leaf. Then use that as a back-stop to build back the leaf.

This is just about the top course of stone before the chimney stack. I'm fairly certain the chimney stack has been rebuilt in brick and then rendered. How worried should I be about the stability of the chimney if I remove any more stones? A wider shot would probably help answer that.

And finally that big lump of cement with the wire embedded in it won't come back through the hole because of its shape, so I think I'm going to have to drop it down the flue. Would it be better to drop it into the upstairs flue that's capped off rather than having it rattle down the downstairs one that I hope to use one day?

 

[Cubist]

I would be taking the KISS approach on this one - ss chicken wire and drop the unwanted mass down the flue you don't plan to use.

 

[fernicarry]

Thanks. That sounds achievable, panic subsiding slightly...

I guess what the previous builder did was make a sort of net bag out of mesh and then push mortar into it. Then once it had gone off snip away the excess around the edge of the bag. Any recommendation on mesh size? I suppose it needs to be small enough to stop the mortar falling through but large enough to ensure adequate contact with the existing masonry. The gap is big enough that I can add some pieces of stone as I go. I suspect there are more of this style of repair to be uncovered.

58 quid a sqm!!

 

[Stevers]

I'm afraid I just know I'd feel bound to attack the chicken wired lump with an SDS drill, whilst holding onto it via the wire, resulting in it going down the hole in tiny pieces. Cubist's KISS approach would be much easier than that with no real downside.

To put it back I'd use a board on a piece of string to stop the wet mortar from going down the flue as you started to build it up to the point where you could retrieve the board and stone it in conventionally the next day.

 

[Cubist]

I think it was Ivor a long time back who converted me to Stainless Steel as opposed to Galvanised chicken wire. Size, I've found, is unimportant as I tend to 'scrunch' it up into a tight ball with lots of hanging/protruding ends that can be used as pressure anchors to hold said scrunched ball in tightly in place together with any other wedges of additional chicken wire if needed. I then use an old sealant inject gun loaded with a lime mortar or plaster to force that into the wire armature to create the needed solid mass.

 

[a twig]

I’m going to provide the opinion you probably don’t want to hear…

My preference would be “while you’re up there”… pull out a few stones to make the hole bigger and provide access to the feathers (at least that’s what the stones making the internal flue dividing wall were called where I grew up - apparently there are significant regional naming variations), repair them and then make the hole good using new stone if required.

Only because in a similar situation I didn’t bother repairing the feathers and just made the outside wall good as we were “never going to use that flue”…

Until 3 years later we did for an open fire and I ended up having to throw an expensive 6” liner with bespoke gather down it due to the deteriorated feathers ruining the draw and causing smoke to leak into the upstairs bedroom…

 

[fernicarry]

Appears I neglected to hit post last night.

Thanks for the suggestions. Better picture showing the context.

.

I got the big lump out by breaking it up with a tap from the SDS so that was a minor victory. I also stripped off some of the cement render above the stone which confirmed that the chimney stack is brick. It was very. very hard. I'll render that section to match the pink render used on the chimney above the roof.

My preference would be “while you’re up there”… pull out a few stones to make the hole bigger

Well, yes, point taken, but... The stones either side are quite substantial so removing those is well above my pay grade. Tbh I think you'd really need to take down everything above that point to do it safely. I'm loath to even knock out that smaller overhanging white stone as the big one above it would have very little support at one end.

I can quite comfortably get my arm into the hole so I spent today feeling around inside pushing handfuls of mortar into any gaps I could reach. Pushing mortar uphill with your finger tips isn't a very effective technique so it may all have been in vain had to try.

Last time we used the downstairs fire (which was easily 10 years ago) the loft filled up with smoke so it almost certainly needs a liner if its to be usable again. Our plaster is stood off the masonry leaving a void that goes the whole height of the building so the leak in the flue could be anywhere along its length.

I started building up the bottom of the big gap using a variation of the @Stevers board-on-a-string idea, the board-on-a-stick. That worked well so I'll continue tomorrow once its stiffened up a bit.

The plan at this point is to use some long narrow stones with one end bedded into gaps in the feathers (seem to be called bridges in this part of the world) and the other end mortared into the outer face.

 

[fernicarry]

After today's efforts. Most of the gap closed up. I think I got the feathers solid above and below this point with more hand pointing and a few stones bedded into the gaps.

Amazingly no stones, trowels or mobile phones dropped down the flue (yet).



Aware that stone should really be laid horizontally but I figure if it gets pressure from above it will be pushed down into the point of the V and that will keep it compressed. These stones do like to fracture along the grain as I found today trying to chip a little bit off the edge of one only for the whole thing to split in two along a different axis instead.

I have a stone picked out and ready which has a nice flat face and is just the right shape for the remaining gap. I'll need to fashion some sort of restraint so that I can pack the back with mortar before shoving the stone in. Thinking of possibly weaving something out of copper wire on account of I have lots of old red and black stuff to hand.



Won't be back at this for at least a couple of days so that will give this lot time to go off.