Suitability of Lime Mortar to bed in Chimney Pots

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Suitability of Lime Mortar to bed in Chimney Pots

We have a brick built grade 2 listed house (built in 1760) where recently we had a new log burning stove fitted by a professional company, that included a new chimney liner and pots.

To do this, we had to obtain listed building consent, where the conservation officer insisted on lime mortar for jointing, pointing & flaunching (flaunching is the setting in of the pots on top of the chimney). As we viewed lime mortar work as a specialist trade and the stove installation company included this as part of their package, I was happy to let them proceed.

Work was carried out in the summer of 2009, but in April this year we noticed quite a lot of lime mortar flakes around the house and on the roof. I sent photo’s to the stove installation company, but they blamed the fragility of Lime mortar (frost damage) and suggested I may like to change to a more robust cement mix, should the local conservation officer allow, pointing out they had only used Lime Mortar because the conservation officer had insisted.

I put this to the conservation officer, who thinks there must be a problem with the mix and it should be re-done, with the correct mix this time.

On a previous house where I had carried out this work, for the flaunching I had used a frost inhibitor with the cement mortar mix & would have preferred this, but I can see the argument it would not be suitable for a listed building.

The Installation company are now being non-responsive when I put it to them the mix may have been wrong.

Should I expect this from Lime Mortar flaunching ?
Where do I go for advice on the suitability of Lime Mortar for flaunching ?

Any advice would be appreciated.
 
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Martin

Like you, I have a listed property to restore. My understanding is that they should have used Hydraulic Lime (NHL) on an exposed place, not plain lime (and definitely not hydrated lime which is totally different). NHL can set in damp conditions and is harder wearing, I understand.

I suggest you find out exactly what they used and ask a company who supply lime products such as Mike Wye in Devon for their expert view - find them or others on Google.

Matthew
 

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