The scary take from all the answers is that there seems to be essentially NO incentive to get the estimate right in this industry. All the incentives are toward underestimating under cover of the slimest excuse possible - just for appearances sake.
For example, you don't know what's in the old wall (but you have a pretty good idea of the amount and odds but you don't mention that) and so you don't include it (because the other guy won't and you have to stay competitive). Instead of including in proportion to the odds. You then later go to the client with "uh oh, we need to fix that. It happens. What are you gonna do?" And the client accepts it. This is mind boggling. If that's not the signs of a thoroughly broken industry, I don't know what is.
Before someone mentions that it's the same for software, not it's not always like that. With experience we got very good at estimating each in a series of comparable projects. It's very possible to fail to estimate large one-off projects. It's very possible to get it right with series. And house building is a very repetitive business. They are all different, but only so different and they are all built of human-sized rooms.
For example, you don't know what's in the old wall (but you have a pretty good idea of the amount and odds but you don't mention that) and so you don't include it (because the other guy won't and you have to stay competitive). Instead of including in proportion to the odds. You then later go to the client with "uh oh, we need to fix that. It happens. What are you gonna do?" And the client accepts it. This is mind boggling. If that's not the signs of a thoroughly broken industry, I don't know what is.
Before someone mentions that it's the same for software, not it's not always like that. With experience we got very good at estimating each in a series of comparable projects. It's very possible to fail to estimate large one-off projects. It's very possible to get it right with series. And house building is a very repetitive business. They are all different, but only so different and they are all built of human-sized rooms.