Is re-pointing the chimney in lime needed if it’s believed to be newer?

[Woodpecker2]

Old part of the house is mid 1800s, however there is a rear extension which the surveyor (not a historic specialist) seemed to assume was also old, however scouring old maps, the extension doesn’t seem present (pre 1900 - it’s not present on the OS map dates 1989-1939 although does that mean it could have been added in 1900 but not there in 89? That’s probably a separate question!!). It also seems to be newer block like the rest of the extension.

the chimney (on the back/newer part of the house) needs repointing due to water ingress and damp on the inside beneath the chimney.

Surveyor has advised repointing the chimney in lime - I am wondering if this is still necessary if it’s a more modern construction? Or what should we look at to determine what material is best? I’ll try and add a photo!

Essentially happy to do with lime if that’s the best material (we also need other parts of the house repointing), but mindful it might be harder to find a professional to do it in lime, and potentially more expensive?

 

[Woodpecker2]

Not the best photos as taken from the ground but gives an idea

 

[Lacan07]

Not the best photos as taken from the ground but gives an idea

View attachment 13843

don't rely on the surveyor, he's guessing. It could equally be something else like faulty flashing, get some roofers up there to inspect. Unfortunately chimneys can be tricky to diagnose and fix.

What you use to repoint is often up for debate, as chimneys are exposed its generally insisted you use a slightly harder material to combat weathering. For old houses a good compromise is something like an NHL 3.5 or even a 5. NHL is much harder than lime putty based mortar but is also breathable. It's a modern form of lime that comes in powder form and is knocked up with water so you don't necessarily need a traditionalist to apply it, anyone competent in pointing can do it providing they observe the instructions.

For modern houses its usually a cement based mix and occasionally they'll chuck a bit of hydrated lime in, whether you believe it makes a difference or not. I think Stuart on here is the resident expert when it comes to mortars and bricks.

 

[aockenden]

Agreed with Lacan, NHL is a happy compromise for a chimney and also agreed that you should have somebody get up there and actually confirm it’s the pointing not the flashing that’s allowing moisture ingress.

Also how refreshing to have a surveyor even use the word “lime”. That’s more than ours did.

 

[Woodpecker2]

Thanks both - that’s really helpful. Yes we do need to get someone actually up there to look. It’s 2x surveyors that report gaps in the chimney mortar essentially so it think that can be seen, but there’s lots of other suggestions (inc replacing the flashing) so do need someone to look. Just want to be ready with an idea of materials for when they come back.

@aockenden we specifically looked for a damp surveyor that said they never recommend damp proof chemical injections and seemed to have an idea about older properties, so there were lots of suggestions around lime, ventilation and lowering ground levels!

 

[aockenden]

Thanks both - that’s really helpful. Yes we do need to get someone actually up there to look. It’s 2x surveyors that report gaps in the chimney mortar essentially so it think that can be seen, but there’s lots of other suggestions (inc replacing the flashing) so do need someone to look. Just want to be ready with an idea of materials for when they come back.

@aockenden we specifically looked for a damp surveyor that said they never recommend damp proof chemical injections and seemed to have an idea about older properties, so there were lots of suggestions around lime, ventilation and lowering ground levels!

Great choice

 

[Lacan07]

Thanks both - that’s really helpful. Yes we do need to get someone actually up there to look. It’s 2x surveyors that report gaps in the chimney mortar essentially so it think that can be seen, but there’s lots of other suggestions (inc replacing the flashing) so do need someone to look. Just want to be ready with an idea of materials for when they come back.

@aockenden we specifically looked for a damp surveyor that said they never recommend damp proof chemical injections and seemed to have an idea about older properties, so there were lots of suggestions around lime, ventilation and lowering ground levels!

If you can actually see gaps in the mortar beds then yes it may well be finding it's way in via these routes.

 

[stuart45]

The blocks like the more modern dense concrete blocks, rather than earlier coke breeze ones, which suggest post WW2. If so, it's likely the mortar was cement/lime/sand mix.

 

[Woodpecker2]

Thanks, that was my thinking that they were newer and stronger