Repointing chimney stack...advice needed!

[jungle_jim01]

Hi....i'm afraid the quizzing is going to continue for a while yet. I've just finished pointing the back of the house....i'll post some pictures soon as it's certainly been a joint effort! I'm now starting on the gable end with the chimney stack. The stones aren't as thick and the pointing is horrendous/non-existent! In a lot of places there are gaps all the way through into the chimney. I'm going to point using 3.5 NHL lIme mortar, the same as the rest of the building. I'm hoping someone's got some 'top tips' so that the pointing doesn't just fall away inside the chimney when i push it in...

thanks again for everyone's advice

 

[robgil]

i am by no means an expert but i would say fully dampen every thing down first and make sure there is no soot or dust. do it on a damp day.

 

[d49xc]

I had to do mine some years ago.
Brick built chimney, lime mortar which had crumbled into just sand in many places.

It was so bad on the north side of the Chimney that I ended up almost rebuilding the north face of the chimney using the existing bricks placed back in their existing positions. Once I found the mortar was just crumbling away and leaving not much to re-point the decision was easy to take each brick out.

Lime mortar 3.5 grade as per you, sharp sand , tried to match colour.
Ensure you are back to stable mortar to point onto.
Dampen down the bricks/existing mortar to prevent them absorbing too much of the moisture in the new mortar.
If it is a sunny/hot day you will need to cover your new mortar to prevent it drying out in the sun.

In my case the top of the stack/pots were OK so I could actually rebuild the stack in sections (4 stack chimney) underneath the top without moving/interefering with the pots at all.(supported bricks off blocks of wood onto the scaffolding where neccessary in places).So I started off on LHS and took off a column of bricks down, rebuilt them leaving the RHS un-mortared as this would be adjacent to the next brick column to be removed and so on across the face of the chimney.

The advantage of opening up the north face of the chmney was that I could access to the back of the other sides to check and to point up the back faces, and that I could ensure the back of the face I was building up was OK as I ensured I always had the next section part removed as I was re-building up the previous.
For the last bit at the top it was difficult but my pots are short so I was able to reach down through the pot to 'sort of' do the back at the top on the last flue.

Very careful not to drop mortar down chimney (some did anyway!)
Finally re-made anti jackdaw nest steel netting over top of pots (they had chewed through the original)
Clean your gutters out at the end otherwise any sand/mortar which has been flying about will get into the gutters/downpipes/soakaways and block them

 

[chuckey]

Its a good idea to have a selection of stiff brushes to remove as much grot as possible dry, else when you wet it, a black stream will issue forth and b****r up the next course down. My favourite is a 30mm wide polypropolene brush as sold by Carrefours in France (30 Ecents), old toothbrushes are also useful. I am still after a narrow bottle brush (6mm diam?) after 6 years looking.
For pointing/repairs where there is no back to the mortar line, I have used a flat piece of plastic (from a milk bottle) with a piece of 16 SWG copper wire looped through holes in it. You hold the two wire ends, shove the lot into the gap and pull the wires, if you are lucky the plastic can be made to lodge across the back of the hole to provide the "back" to the hole. The excess wires can be cut of when the mortar has gone off. The difficulty is maintaining tension of the wires while you do the job. I have considered marketing a gizmo it'll be less then a fiver, but real brickies just push stiff mortar across the front of the gap and call it a job done.
Frank

 

[jungle_jim01]

thanks for the tips. Perhaps i should mention that my chimney is made with sandstone blocks...a tad heavier to remove and rebuild so i'm hoping it won't come to that...i like the idea with the plastic...might have a play.I had wondered about stuffing the back of the joint with newspaper but then there would be that small portion without mortar. Any more ideas welcome.

 

[philpjuk100]

I am still after a narrow bottle brush (6mm diam?) after 6 years looking.


Frank

these are available from frost classic car restoration,£8.50 for a set of three.

 

[chuckey]

Thanks Phil.
Frank

 

[LadyArowana]

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