What size stable for a 18hh heavyweight?

[Achinghips]

I have stables 12 x 12 and am thinking of taking a partition out to make it 12 x 24. Anyone else have a big heavy? What size stable do you manage with?

 

[AdorableAlice]

16 x 16 for my last heavyweight

 

[TigerTail]

My field shelter is 12 x 18 and my 16.3 friesian only just fits in it, if she were to be shut in it would have to be at least 14 x 24 for comfort and safety, wouldnt want her getting cast!