Take whatever number you are thinking should be enough to get you most everything you want and then add 50%. Also, be sure to take into account the cost of updating/upgrading your house's mechanicals to handle the new space. You may find you need a new HVAC system or significant plumbing or electrical work, depending on the age and condition of the house.

Unfortunately, there really isn't any way to answer a question like this without knowing quite a bit more about the situation. Even if you were able to find someone else in your local area who added the same amount of space, the cost could still be quite different due to differences in the house, the lot, and your choice of fixtures, fittings and finishes

Hi Linda, Thank you very much for your input. This explains many things. Can you suggest the best way of approaching the situation? We've had some contractors come over and their estimations range from 20K to 100K. We're confused as to how much we should actually be prepared to spend on such a project. Thanks again for your input.

I suggest talking with those contractors and ask them what is included in their estimate. Tell the cheap guys you are concerned that their estimate didn't account for all the possible work necessary and ask them how to tell you in more detail what updates they expect to do to the plumbing and electric

Approach the more expensive guys with a question about why should you pay that much money when you have gotten estimates for less than half the price for doing a similar amount of work...ask them what special features are they bringing that the other guys aren't including.

Ask each of the bidders where they get their cabinetry and go look at the materials they are proposing...do you want top of the line materials or you are satisfied with midrange products? Fixtures and faucets and tile vary tremendously in price and could account for a significant portion of the estimate. For example, if you are looking at buying 300 sq ft of tile at $5 per sq foot, that cost would be $1500. But, upgrade to $15/sq foot and you've added another $3,000 to the overall cost although the labor cost won't be much different. Are you looking at a $200 or a $600 faucet, a $400 bathtub or a $2,500 tub?

Another factor which could be adding a significant amount to the estimates is one that homeowners often don't consider. Does the contractor really want to do the work? The low bidder might be really hungry for work while the expensive guy might be booked up but willing to push off a less profitable job if you would happen to be willing to pay his dream price. The high estimate might come from someone expecting to knock down the bid in negotiation but throwing out that price tag to see if you flinch.

Personally, I prefer to work with small outfits where the person who bids the job also supervises the work directly and preferably even does a portion of the work himself. I don't want to work with a salesman who is going to promise you whatever it takes to get you to sign and then takse his 20% commission and immediately dumps the job into someone else's lap.

It is an old joke, but the message fits - A guy walks up to a girl in a bar and asks her if she would sleep with him for a million dollars. So, she looks him over and agrees. Then, he asks her if she would sleep with him for $50 and she replies "hell no! Do you think I'm a prostitute?" he replies "we've already determined that, now we're just negotiating the terms." Some contractors approach jobs using that philosophy...I don;t really want that work but if they're willing to pay that much, I'm willing to do the work"