Commercial. I measure but it's really it's on both how long I think it will take and size. I mean the rate per metre will fit the job.
As Shaun, I too find commercial are only based on lowest price, and what's worse is often selling myself doesn't help because I only get to see the (usually young girl) office dogs body who's simply gathering the quotes to be passed onto the decision maker who goes with the cheapest. - Then moan they got a sh*t job
Theirs always some desperado that will do it lower than anyone else! lol