Sorry didn't see your second post.Overall width is 1320mm
Sorry didn't see your second post.
For pure DIY I wouldn't recommend removing any of the outer edge 9" brick walls that form the original builder's/structural opening. Which leaves you with an opening of around 870mm.
If you can lay bricks/blocks then you could build new walls to form a wider builder's opening, then the new lintels can support the existing chimney above.
The arch will hold - but as you are spooked by bad advice from ignorant posters #7 & #10 the thing to do is stop work on the chimney breast. Perhaps call in a builder or bricklayer?
Poster #22, given that in the past you have copied, word for word, text from my various historical posts I find it strange that you now claim to see "poor and risky advice".
To be fair, why dont you explain where my advice is "poor" - please be explicit?
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