Expansion gaps or contraction expectations?

[syne]

So, I've gone with the super duper cheapo euro cell for my extension as I'm running out of money and well, they're cheap. 

 

But all the instructions state leave 5mm for expansion on each edge. 

But if I'm fitting them on the hottest day/week of the year is that 5mm actually necessary?

Surely come autumn when they start to contract that five mill will become.. More.. 

 

Nothing like overthinking is there.. 

[nod]

5 mil is correct I wouldn’t think UPV frame would expand or contract much 

Any less and you will struggle to plumb the frames up