DIY Doctor UK DIY Forums

i have recently purchased a very small wood burning stove for a stone built outhouse, the flue i require is 3m long but can not afford the real deal as they are so expensive. Would i be able to use a length of 4" cast iron down pipe instead? If so how can i insulate the pipe as it passes through the flat roof?

The flue of a wood burner needs insulated for a reason......it gets very very hot and if you continue this madness you will eventually touch it and get 2nd degree burns if you are lucky.
I suppose the place may burn down before you hurt yourself but either way I can see much sadness.
The building regs man would have kittens if he seen what you propose.
Please please go out and buy a proper flue.......

No you can't use iron pipe becoz its get hot when hot air passes through it and a cemented and insulated pipe not create this problem.