electric fire

[Connemmara]

In order for my fire to work correctly I need to block the hole in my chimney breast - I have tried to use many tapes to tape the cardboard to a piece of cement to block this hole but the duct tape is not holding it together any ideas to get this cardboard to stay put Thank you

[alavahalf]

Tape wont stick onto cement very well...Why not try a bit of plywood instead...cut it so it fits fairly snugly .... and just Gripfill round it.

[johnk]

Try a piece of thick polysterene or foam cut to a tight fit in the hole. This should be self supporting and any gaps will give you a bit of ventilation

[AlBags]

You should really use a specially cut to fit piece of fibre-board for this (the modern equivalent for asbestos sheet)
Builders merchants keep it in several widths (as builders use it for roofing gable ends, among other things)
You can also use galvanised sheet.
Then it should be screwed in place.