The pics are of a 65 year-old chimney in a temperate climate, not subject to freezing. The chimney was retrofitted with a natural gas space heater (and flue I assume) about 7 or 8 years ago. I can’t see what’s inside it as the 4" flue extension and cap has been cemented in place. You can see a 1/4" horizontal crack running the entire length of the eastern (non-prevailing weather) side and part of the southern, ie shaded side (southern hemisphere here!). It’s as though this side has been lifted up and looks relatively recent. The gas heater appears to be working well with no signs of combustion or venting problems. Any ideas?
Whats the cap look like ?
Is that the issue at the second ridge ?
You never say where you are ?..no profile or website.
I see no cap. water intrusion issue most likely ]
Call for a mason.
I see moisture indicators (discoloration)…
http://i572.photobucket.com/albums/ss162/dandersen_02/DSCN0004a.jpg
And I see a chage in brick texture from that moisture.
http://i572.photobucket.com/albums/ss162/dandersen_02/DSCN0004b.jpg
But I wasn’t there…
Good catch Dave.
The bricks have a different composition which means different expansion limits.
You should always repair with the same composition brick or level off and build new, not weave in.
David that new picture ir tech is amazing… Lol.
My new IR camera watch can do that. $89.95 plus shipping and I got 2 for the price of one!
Paul, brace yourself for the fallout!
Naw, no one would question my IR watch would they?
Not as long as you’re wearing your glasses too! :mrgreen:
We really need a “LIKE” button for these posts! Nice Michael!
Simple digital photograph tuning at work…
No IR involved here…
What Sotfware Dave? Nice Work! 
Thanks Bob - I’m in Adelaide, Australia. I’m just starting out so no website or profile yet.
Yes, that’s the area - it’s my house - the whole mortar joint under that course on one side has opened up for some reason - there’s a close-up in the second photo.
As far as I can tell, the brickwork appears to be original, although the house was built in the post-war period when building material shortages were common, so possibly bricks with different compositions were used on the chimney (out of site, out of mind?)
As I mentioned though, the crack looks relatively recent, so possibly dates from when the chimney was capped at the time of the gas heater/flue installation a few years back.
Condensation? There’s also efflorescence in that area. Last time I checked the cap was intact, but I’ll post a photo when I get up there again.