Chimney stack repair or rebuild?

[Sismithin]

Hi all

Since I bought my first victorian cottage home back in May 2014 I've used this forum no end and have always found an answer to my question without having to post whilst doing my renovation work.

My first question though now...

I'm having my chimney repointed tomorrow and my flashing re done by professionals. Once the work is done however I'm thinking of sealing the whole stack in a water repellant/sealer as I'm starting to get some spalling on the entire stack, and I think it might help? No? I can get up on a ladder after to spray or brush the sealant after the mortar has dried etc.

Would the Screwfix no nonsense water repellant/sealer be a good product to use? It has great write ups. - http://www.screwfix.com/p/no-nonsense-water-repellent-seal-clear-5ltr/57474

Thanks in advance

 

[ree]

It would be worth your time to go up now and take some pics of the stack, the flaunching and the flashing, and post them on here? Is it just one stack?

"spalling" where - inside the flue or on the face of the stack? Are the flues in use - using what?

Have all your flues been swept & smoke tested?

 

[bobby spray]

first off, if you're repointing your stack i hope that you're using a lime based mortar. Cerement based pointing will likely exacerbate the spalling you are experiencing and may even be the cause of it. I would counsel against sealing your brickwork as you would be likely to trap moisture behing the sealant and blow the bricks.

 

[Nige F]

Better off climbing the ladder and taking pics - post here and we can appraise the work

 

[Sismithin]

Sorry guys for some reason I didn't get an e-mail to say I had replies to my question

This image I took in summer, I climbed out of the velux window and snapped these while I was lining the flue.

The chimney stack has 4 flues, two have had the pots taken off and sealed top and bottom, one is lined with a steel flexi liner and is in used with a wood stove, the other is open both ends but not used at all.

Roofers are on hold at the moment whilst I deliberate.

As you can see it's in poor condition and the previous owners like to botch everything and now I'm paying the cost. The cement mortar pointing that had been done looks like it has too much sand in and is just crumbling, there is very little if any lime mortar still there or at least visible...unlike the rest of the house which has been repointed with proper lime.

The other side of the stack is similar but there are 4 bricks together where nearly half the bricks thickness have spalled away and fell onto the neighbours drive way.

Thanks for your help

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• Sismithin
• 14 Mar 2015
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[Sismithin]

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• Sismithin
• 14 Mar 2015
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Here is the full stack which has been cut down by half at some point...again very botched unfortunately.

Also just to note I have repaired the flaunching that is damaged in the picture, it's been built up looks better now.

 

[danielroofer]

If this was a chimney on my house I would get a scaffold tower up and lower the stack down to gutter height and then rebuild it, new bricks and new lead flashing. I accept that this isn't going to be cheap but a good roofing company with an experienced bricky on the team could do this in a day.

Some of those bricks are crumbling, the mortar is shot to pieces and the bricks have collapsed onto each other. The lead has come loose and overall the chimney stack is in a poor condition.

You could save money by cutting out the loose mortar and repointing it, also repair/replace the lead but I suspect that this will only delay the inevitable, it needs a rebuild from gutter height upwards. In my opinion.

 

[Dextraneous]

Are the chimneys in use! Getting an alternative flue for the woodburner and removing them below roof level and getting it slated over might actually be a cheaper option and provide possible alternatives in the future (viz removing the stack entirely and squaring off rooms)

 

[Sismithin]

Hi guys, I had a second opinion from the roofers due to repoint the stack - and its exactly the same as you mention. they said it really needs knocking down and rebuilding.
Just for interest I have just been up on my sketchy scaffold tower and took a few pictures.

On closer inspection you're certainly right it does need rebuilding.

I have no idea why the images have all rotated on upload but you get the picture.

Thanks for all your help, I'm shopping around for builders now.

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• Sismithin
• 16 Mar 2015
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[ree]

No it doesn't. The stack is essentially sound & doesn't need rebuilding. Here's what you might consider doing:

1. Sweeping and smoke testing all four flues.
2. Venting, or leaving open, the flues at their chimney breast base.
3. Removing the flaunching and pots.
4. Dropping the top three courses.
5. Set four pots back on the stack - four pots will give a balanced, traditional look.
6. Build up the flaunching to cast off rainwater.
7. Rake out to a depth of 20mm to 25mm and point up with 3:1 NH lime & sand.
8. Remove all damaged bricks.
9. Re-fix or replace the lead flashing.
10. The back gutter must have a central high point and shed water from the high point to both sides - google chimney cricket pics. You only need a slight fall, say 25mm to nothing.
11. Replace cracked slates around the chimney stack.

 

[Sismithin]

Hi Folks

Just an update for anyone interested.

I took onboard the great advice on here and also got another opinion from a roofer who gave me an excellent quote for the job and some other work at the same time who I went for.

Basically the stack has been repointed so far, a new lead apron at the back, lead sealed, re lead sealed front apron.

3 more round pots to go on (reclaimed for a total price of £10)

new flaunching to finish the stack.

Rebed all ridge tiles
repoint rear chimney stack and replace lead apron also.

What do you think of the work so far. I'm really impressed with the guys doing, very professional and tidy.

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• Sismithin
• 20 Mar 2015
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• 20 Mar 2015
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On the last picture should I be concerned about that?
Thanks again

 

[Sismithin]

PS forgot the picture of the chimney pots - there not matching but they cleaned up well. Not bad for £7.50 including the pepper pots.

Even though 2 of the flues are sealed off I want them all to match.

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• Sismithin
• 20 Mar 2015
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[ree]

All the spalled bricks have been replaced.


1. Do you have pics of the flaunching?

2. The last pic doesn't show lead soakers - pics of that side of the stack would help? Does it show sand and cement or a fillet of bitumen? It needs investigating.

3. Some of the lead is the old lead re-used - i presume you know that?

4. You have 4 flues but only 3 pots, unless you re-used the square pot? The smaller pot(s) should go in the middle for balance.

5. The old, smeared on, thin ribbon of pointing has been "pulled off" - but not raked out to a depth of 20mm to 25mm.

6. The back gutter and the house gutters need cleaning out.

7. Patination oil would have helped.

8. Above i left you a list of 11 suggestions - not all have been carried out. Just saying.

How much were you charged? DIY'ers following this thread like to know costs.

 

[Sismithin]

Hi Ree thanks for your input.
Flaunching is being completed tomorrow.

I'm going to investigate the soakers tomorrow when the guys return to finish it all off.

The lead hasn't been replaced as it's not in bad condition, but the a new piece has been used on the new rear apron. (Had a roll of lead already)

The square pot is coming down, the round pot with the cowl/rain guard is staying and the 3 pots pictured separate are going up. I know they are not matching but will look ok from the ground and better than current combo.

All the pointing has been raked out to about 25mm - the whole street and roof/gutter is full of the old sandy mortar, it took one chap 5 hours to do and burnt out an angle grinder in the process.

Gutter and back gutter cleaning to follow after flaunching is completed.

They are going to finish it off with a waterproof breathable membrane applied all over also.

Ridge tiles and rear chimney to be completed tomorrow (Saturday)

All in everything for £500 including materials and VAT and apparently guaranteed. (I supplied replacement slates and bricks, lead, and chimney pots.
Scaffold tower was borrowed as a favour from my neighbour which has helped keep the costs down


I really appreciate your expertise and help

All the spalled bricks have been replaced.


1. Do you have pics of the flaunching? -

2. The last pic doesn't show lead soakers - pics of that side of the stack would help? Does it show sand and cement or a fillet of bitumen? It needs investigating.

3. Some of the lead is the old lead re-used - i presume you know that?

4. You have 4 flues but only 3 pots, unless you re-used the square pot? The smaller pot(s) should go in the middle for balance.

5. The old, smeared on, thin ribbon of pointing has been "pulled off" - but not raked out to a depth of 20mm to 25mm.

6. The back gutter and the house gutters need cleaning out.

7. Patination oil would have helped.

8. Above i left you a list of 11 suggestions - not all have been carried out. Just saying.

How much were you charged? DIY'ers following this thread like to know costs.

 

[Sismithin]

Right chaps the work is finaly complete. Now I'm reverting back to the original question slightly. My roofer hasn't sealed it with the Thompsons Ronseal breathable water seal stating it didn't need doing since it's all be re pointed despite saying at first he would. I'm not going to ask him back to do it as he has worked very hard and done a great job anyway.

Whilst I still have the scaffold and for the sake of £10 is it worth doing anyway just to prolong the life a little more or will it cause more harm then good on nice new mortar??

I was thinking of using this and spraying it on with a pressure pump sprayer?
[/url]http://www.screwfix.com/p/thompsons-water-seal-clear-5ltr/52043
I can get it much cheaper than that at my local hardware store. 2.5 litres for £5


Thanks