Flue pipe creeping upwards, now big gap between flue/fire???

[Markymilarky]

Hi Everyone,
I have a woodburner and a 8" single skin s/s flue pipe going all the way up to the top of the house.
As the fire in the woodburner cools the flue pipe creeps upwards at the connection between the woodburner and the flue pipe. Once it's cold there is a 1" gap between the top of the woodburner and the bottom of the flue pipe, So the smoke just comes out to the room.
I've done something wrong or not fitted something but don't know what.

There is a cast collar that is part of the woodburner and it has a re bait of 15mm to take the flue pipe. I have put 1 length of s/s pipe into this re-bait and then fire cement around the joint.
Then between the top of this pipe and the bottom of the pipe that comes down from the roof there is a gap of 6". Here I have a joiner piece that tightens up on both pipes with collars and bolts. Somehow the bottom pipe creeps up into the collar when the pipe cools.
Any Ideas please????
Is there supposed to be a collar at the top of the woodburner that has screws in it to mechanically fix the the flue and the woodburner together ??
I,m stuck on a solution.
Thank you in advance for any help. Hope I've posted in the right department.
Regards, Mark.

 

[Markymilarky]

Hi Chums,
nobody has an answer, could anyone direct me somewhere that I could find this info please. I'm stuck.
Cheers Chums.
Mark

 

[Hugh Jaleak]

Try www.hetas.co.uk the website for the Solid fuel advisory service, they might be better placed to help. Meanwhile you would be best advised not to use the woodburner until its sorted.

 

[Markymilarky]

Hi Hugh,
Thank you very much for the info, much appreciated.
We have 2 c/m detectors on and are pulling the flue back down every day at the moment but thank you for your the advice. I need to get it sorted fast.
Regards,
Mark