Our fifth wheels are mercs 1.27m and renaults 1.32m.
waynedl:
Sounds like a lot of effort, can’t I just park it next to one that’s got the height on it and guestimate it ?
No need - just get out your trusty Truckers Road Atlas, and find a bridge that’s alleged to be around the height you think the trailer might be. Then go and drive under it…
I use this, it’s great, portable and it never fails, will stand up straight next to trailer no problems, height checked to the millimetre 
http://www.screwfix.com/p/fatmax-pro-short-tape-measure-5m-x-32mm/32477
Just drive at bridge at speed, if you hear a Big Bang! 
you know it’s a low bridge! 
truckers bridge atlas, plan your route and get home safely Friday peoples! 
FFS not rocket science
so how much extra do you add on for immigrants on the roof
HAIRYGORILLA:
so how much extra do you add on for immigrants on the roof
Common practice to subtract 2 inches if they aint paid or ask one of em to hold the tape if a group bribe has been received.