Oversizing lintels/steel to ensure minimum bearing

[BadgerBadger]

I'm looking to order our cavity lintels and a handful of longer steel PFCs that form lintels.  Blockwork hasn't gone up yet, but I know I need a minimum 150mm bearing on each end.  Should I be oversizing the lintels/steel that I order to ensure 150mm bearing? Or simply adding 300mm to the design opening width, and then ensuring brickies don't make the opening any larger?

 

Is it likely to be problematic if the lintels end up with a longer bearing?

[Miek]

Longer bearing on longer spans is a good idea IMO, my building inspector had the view that longer is better too. I've gone for 300mm bearing on the steels spanning my patio doors at 4.9m . Sometimes your SE will specify bearing requirements for structural  members in your calculations.

[George]

Longer bearing doesn't matter but for a normal sized window (not 4.9m + that is a proper opening), you are safe just adding 300mm. A few mm here or there shouldn't matter. 

 

The structural drawing should be highlighting where something is unusual or extra bearing is required.