Case Studies

Date: February 2012

Flue details: 1980’s terracotta lined flue with an open fireplace and no cowl or bird guard

Reason for survey: To test some new equipment, the flue was not showing any symptoms or cause for concern and was believed to be working fine.

Result: The flue failed the flue integrity test and was leaking 75% more than the allowable rate for that flue. From this a CCTV survey was carried out to ascertain the reason for the high leakage rate.


At 0.38 seconds: You can see the first joint from the top of the flue which has a gap where there should be mortar.

At 0.59 seconds: You can see the second joint from the top which also has a considerable gap and some missing mortar with the mortar that is present showing slight cracks.

At 1.26 minutes: The upward angle shows that the joint is misaligned.

At 1.48 minutes: Mortar is missing in some parts of this joint to show bare brickwork. The mortar that is present is showing slight cracks.

At 2.30 minutes: Once again there is a gap between joints showing missing & cracked mortar.

At 2.40 minutes: It is apparent that slurry has leaked into the flue via poorly made joints in liner sections

At 2.47 minutes: A very deep crack is evident.

At 3.31 minutes: This joint shows missing mortar however compared to the previous joints it is in fairly good condition for a 30 year old flue.

At 3.42 minutes: An upward shot showing the misalignment of the joints and the existence of cement squeezed into the flue that was not removed during construction.

At 4.23 minutes: A vertical crack is apparent.

At 9.50 minutes: This shows a big gap in-between a joint which also has some missing. mortar.

At 11.00 minutes: A large, tapering gap can be seen evidence that the tube is misaligned.

At 12.00 minutes: Another joint is shown not joined sufficiently with cracks and missing. mortar.

At 14.50 minutes: Another joint is shown to be missing mortar.

Advice given:

From the footage collected it is apparent that the flue was built without properly aligning the terracotta tubes, or sealing them properly. Given the high rate of leakage it is more than likely that the backfilling around the tubes is either incomplete, or non-existent.

These faults are, realistically speaking, irreparable. Using it as an open fire shouldn’t be too risky as the flue has a strong draw, but some caution should be taken if installing a stove. If there are any creosotes caused, then these could be able to penetrate quite badly in places. Relining advised.

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