the point of the contract is so that there is no interpretation necessary - in theory.
After re-reading your original comment...if you are so worried, I would be there and not let anything slide. Is there anything in the contract that states "contractor responsibilities" and how this is reflected in the finished work?
Regarding mechanics lien...my situation: Bathroom remodel..as things progressed I noted more and more issues, things left unfinished, things done incorrectly, etc. I brought them to their attention, and they came out to look at them (the business people). I have emails of them admitting they did X, Y and Z wrong, telling me they would put a plan together to resolve them. Day after they asked for a milestone payment, to which I said I would need to understand the plan going forward first. Couple of days later, they terminated the contract (well within their right to do so "for convenience"), claiming I "refused to pay" when in fact all I did is I asked for full itemization of the project to-date (overages on allowances and such).
So, great - looks like they fired themselves. They insisted they were owed money. There is money I owe them, yes, but when I calculate the change order(s) I pre-paid for that had not been done, some items that had not been started that had been part of an earlier milestone - the dollars started to net out onto my side. i.e. I have already paid you enough for the work done. We failed to come to an agreement at mediation. Days later they file a lien for the FULL contract amount.
At this point I am furious. The final milestone on the contract states "upon project completion". Since they did not complete the project, they are not entitled to that payment, so immediately the lien amount filed is grossly over stated. Furthermore, to correct their mistakes (and I have all the photos and building codes to prove what they did is OUT of code), it is going to cost me a ton more money. They want me to pay them full contract amount, then turn around and pay someone else to correct and complete the job. Tell me where I went wrong here. I vetted them through BBB, Angies List and even went onsite to look at a completed remodel they did down the street. Also recommended by other neighbors. I don't know what else I could have done. Thank goodness I was there everyday to catch other things before they got worse.
Still currently in legal discussions...I am in about $3K in legal fees now.