another option i was thinking of was to go ahead with the slightly larger dimenison and then apply for retention planning?
i will ask my engineer but i dont think i will be asking my planning offier (very unhelpful)
to answer onq we designed the house ourselves, i come from a construction background, and i got a freind to draw it up - the house currently meets building regs, i just was to better insulate!
If you're not formally trained to interpret the building regulations - and your late change to the cavity suggests this may be the case - how can you give that assurance?
I know plenty of people from a construction background who haven't a clue about the current Part L requirements, never mind Part F.
You would be wise to have the entire design checked
before proceeding to site by someone competent to interpret ALL the building regulations, not just Part A Structure, the Engineer's speciality.
I also strongly urge you to agree any variation to permitted drawings with the local authority before you commence, because if the planner is as difficult as you've suggested, he could strictly interpret your permission and half work while you get retention permission.
Did you not see that programme on recently about the house being delayed 5 months due to planning "paperwork"?
Measure twice, cut once and stick to what you're good at
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All advice on AAM is remote from the situation and cannot be relied upon as a defence or support - in and of itself - should legal action be taken.
Competent persons should be asked to advise in Real Life with rights to inspect and issue reports on the matters at hand.
My best advice is that you should retain a competent building professional to advise you on these matters.