[RichardA]

I would appreciate any advice please -- I am dismantling aluminium green house that has been in place 38 years. Need to move to allow us to build a bungalow. Nuts and bolts are original ones and are pretty much seized up. Nuts very soft so easily rounded and to make things worse seem to be a very odd size, midway between 7/16 and 3/8 in old money and between 10 and 11mm in new spanner sizes. Cant get access with mole grips or shifter spanners. Trying to knock nuts off seems very risky as aluminium sections very thin.
Any suggestions would be appreciated please. Regards.R

[madcat]

Have you tried squirting WD40 into the threads and leaving to soak/ease?

[Lardman]

Try tighten them a tad before hand - seriously.  If you're not bothered about them the easiest way to shear the bolt is to tighten into itself.

None destructively - WD40 as Madcat says or get the blowtorch out and warm them up ... it should be enough to break the stiction, careful though it will act as one big heatsink.