Gas Safe have released the above technical bulletin to provide guidance to engineers to ensure that horizontal chimneys and their terminations are correctly secured and sealed. Note – The manufacturer’s instructions should always be consulted first
Within it explains that there are 2 different requirements for the installer to consider;
- Weather proofing of the termination to prevent weather and/or combustion product entry
- Security of the chimney to prevent disconnection
It explains that a correctly installed weather collar is sufficient enough to prevent the ingress of weather and combustion products.
As you can see from the diagrams opposite it sufficient enough to just make good the inside of the flue to secure the flue and use just the weather collar externally to prevent ingress.
Full details can be found in the full Technical Bulletin by clicking here