Removing redundant flue

[mints73]

I have a redundant wall mounted water heater with a large " silver " rectangular balanced flu through to the outside of the bungalow.

I find I am getting cold air coming through now that winter is here so has soon as things improve I am going to get rid.

Is the best way to fill the hole with bricks on the outside and use brease block on the inside, as regards morter due to freezing temps at night should I wait untill warmer times.

 

[45yearsagasman]

The weather as it is I would wrap plastic on the flue outside to stop wind getting in and wait for warmer weather b4 bricking up.As long as this old heater is disconnected from the gas/water supply there is no problem.

 

[foxhole]

If you seal the external as suggested you should be able to block-work the interior hole as it will be warm enough.