Hi ,
Looking to install a wood stove and need to take the pipe thru an old stone wall which is rendered but I know is made of a varied mix of sizes.
The hole will be quite low down leaving approx 2.5 metres above and I am just a tad worried that something bad could happen.
Anyone done this ?
To be honest it would pay you to get a professional maçon to do the work if you don’t feel confident or understand what is involved to stop any collapse. OH carried out gros oeuvre contracts back in Bretagne where it was thick granite walls but usually the centre of all those walls were loose rubble and cowshit so it was done very carefully and supports where necessary so any openings would not go larger than what was wanted. You can’t mess with a gable end if that is the case here so best get a pro and the work will be covered for ten years too as flue pipes get very hot and he will know how to line the wall inside to prevent any other damage from the heat.
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Depends on what your local stone is, I hit flint part way through which was a pain as even diamond core bits struggled, the rest was limestone which crumbles and can jam up the core bit so regular clearing is neccessary. Ended up removing the flint and casting a refractory cement ring around the hole for strength and durability.
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You shouldn’t have any structural problems making a round hole through a stone wall. I did one last year for a 150mm flue by using a 100cm 13mm diameter SDS bit. I drilled a central hole, marked a circle about 175 mm diameter around the central hole from both sides and then drilled every 25mm or so from both sides. Then knocked the bits out with a lump hammer and cold chisel
You can hire a core drill, but over 100 mm tends to be a professional rig that needs clamping to the wall and lots of water
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I have knocked out a few widows in old walls to enlarge them in the past, making a hole for a flue pipe if your quick and pack in cement is not going to make much difference to the integrity of a wall
Errrr you can go to prison for that 
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I have made three doorway size openings in old stone walls made of irregular ‘field stone’ (and whatever else was handy at the time of original construction), over the last 20yrs and have never had a problem with any serious collapse. Of course the odd stone will fall out from above the opening which is to be expected, but as you only need a relatively small hole it shouldn’t be too much of a problem for you. It is really quite amazing the way that a wall built without the use of mortar will hold together under the onslaught of a Kango Hammer.
The fact that you have a good height of wall above where you need to break through it is actually a good thing as the weight will it hold together well. Having to break through near to the top of a wall is far more problematic.
First, drill a 20mm hole all the way through the wall, and then work from both sides alternately towards the middle to enlarge the hole to the size you need. What you will end up with is two roughly cone shaped holes that meet in the middle.
For info; If the Kango or drill suddenly takes on a ‘ringing’ note then STOP IMMEDIATELY, hopefully before you break either the tool or your wrist ! Such a pinging noise means you have hit something really hard such as big lump of marble, and you will probably have no choice but to excavate around it and take it out whole.
For your task, I recommend that you find yourself a length of concrete drain pipe that has a larger internal diameter than the exterior diameter of the flue pipe you wish to pass through the wall. Make the hole through the wall, install the concrete pipe, and then (from both sides of the wall), pack around the outside of the pipe with a not too wet concrete mix. If you have any concerns at all about the integrity of the structure (or just for your peace of mind), then add some lengths of steel re-bar along the outside of the concrete pipe amongst the wet concrete that you pack around it.
The air flow through the concrete pipe will help to shorten drying time.
Once all is dry, you can then thread your flue pipe through the concrete pipe with ease, packing around it with some non combustible material of your choice to stop any draughts.
The important thing is to accept that you are going to end up with a larger hole through the wall than you actually need, and so you will have to spend some time packing the wet concrete around the concrete pipe. Ram the wet concrete in with a length of wooden batten, and add in some of the stone bits from the debris, and you will end up with a structure that will still be just fine 100yrs from now.
Basically, making the hole will be the quick and easy part, and it will be the making good afterwards that will take the time.
By the way; Handling wet concrete is very drying to the skin of the hands, so add a bottle of good quality hand cream to your tools and materials list. 
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Wear gloves
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Not a hole in a wall but your explanation did make me think of this
https://www.youtube.com/watch?v=yShvgXZQBTs&feature=share&utm_source=EJGixIgBCJiu2KjB4oSJEQ
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Wot he sed!
Yes, indeed at first glance that would seem to be the obvious answer. However, I have never found a pair of gloves that are both robust enough to withstand the sharp edges of the gravel in wet concrete, AND, thin enough to allow the placing of a handful of the stuff deep into a hole in a confined space. I start off wearing them, but then there always comes a time when they either tear at the finger tips, or just become an annoying frustration to manual dexterity.
So just like a kid in a sandpit, I invariably end up with mucky hands that I rinse fairly frequently in a handy bucket of tepid water.
Or perhaps the short answer is that I just like playing in the muck.
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Grown ups use tools and not their hands
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I agree, I rarely use gloves except when it is cold for anything, use what I always called a mortar board or a Plasterers Hawk and a trowel
Try telling that to a Potter, Baker, or Pastry Chef to name but a few John.
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Except none od those are using a caustic substance
we all have our own way of doing things…
I always use gloves when using eau de vie in my recipes… don’t want to leave my fingerprints on the bottle/glass… hic 
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I suppose some folks must have more sensitive skin than others. Never really had a problem with it myself, but then I do rinse my hands frequently simply because they are all mucky. Same thing with using bleach. I can clean a sink or bath with a cloth and neat bleach and not have a problem apart from smelly hands. The wife marvels at how I can seemingly handle hot plates which she needs oven gloves to pick up.
Probably boils down to the old adage of ‘Where there’s no sense there’s no feeling’.
Anyway; Hope you are doing OK John. Not like you to be online here at past 3am.
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The hole in the wall - Of course a boring tool would make a neater hole, but I would say it isn’t necessary. Break away the joints around the stones and remove the stones, with a hammer and chisel if the mortar is reletively soft, with a small jackhammer if it’s very hard, work from both sides of the wall if possible. The wall is unlikely to collapse, a stone or 2 could drop down.
Hands - I have always worked with bare hands for everything, but recently (since about 50 years old), cement and plaster makes my hands very dry and cracks the skin, strange!
By the time you have read all these posts you could have finished by now😀
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Hi ,
Thanks for all the encouragement - I have done some stone work here in the past just not this specific thing - a bit of a one off .
So its looking very likley that I shall be going ahead in the coming weeks and fingers crossed no disasters .
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