As discussed in my previous post, it is imperative for companies bidding on public projects to comply with specifications. If they do not, their customers or suppliers will hold them accountable for any oversight. Even if they do comply with specifications, business relationships or a customer's buying power (monopsony power) may cause a careful company to eat the cost of someone else's oversight.
In order for a careful company to cover itself, there are a few things the company should always do on public projects. In many cases, these would come in handy on private projects. First, never simply state that you are specification-compliant. Instead, state exactly the drawings and specifications on which your bid is based. It might get tedious, but to note exactly from which sources you get your bill of material or services can go a long way in protecting yourself in the event of later conflict. It is also prudent to date the drawings and specifications. Sometimes, these can change as a project proceeds.
When an oversight occurs and material or services are omitted from a bid, positively stating that you were only shown X number of drawings and specifications may exonerate you. Of course, if you have all of the specifications, then it is your responsibility to examine all pertinent documents to determine what the requirements are. But if you are in an industry where you typically do not receive everything, it would be prudent to note just what you are receiving. If you do, it puts the onus on either your customer or supplier who did have full access to the specifications.
Second, any time you get approval for a deviation, note it, and to whom you talked. If you can, get it in writing. On public projects, addenda are typically issued that may provide for this. Third, be redundant. Even if something is implicit in an industry, not everyone will see it that way. Again, it may be tedious and time-consuming, but you should not assume something is implied in your bid. You may have a page of notes or exceptions, but it can save you a lot in the long run.