We need to make a 1300 sf house into a 2300 sf house. How do I estimate the cost?

Question

We're trying to figure out rehab costs to add square footage.   Anyone have a good rule on thumb?  We need to add 1000sf.  (Additional  bathroom, bedroom and expand the kitchen/dinning), Basically "blow out"  the back of the house.

Jim M. · Answer

I just finished one a couple months back and was all in about 160k including renovating the existing structure which was about 1200 sq feet give or take.  This was pretty high end as well.  Custom cabinets in all baths and kitchen, hardwoods in all rooms, granite, etc.  Those finishes dictate quite a bit of your budget.

Eric Bauman · Answer

I looked into this myself. What I did was to see how much the individual parts of the project cost, like framing, foundation, plumbing, insullattion, etc. Then add every thing up to get a good approximation of cost. That way when bids get put in you know the general ball park they should be in, and what kind of return on investment you could be looking at. Good luck.

Mike Fallis · Answer

Thank you for all the feedback.  At this point, I am just trying to figure out my offer.  This is the smallest house in the neighborhood by 1500 sf.  There is no basement and I am just trying to figure the easiest way to add sf and determine if it is cost effective to compete for a higher ARV.

John Rooster · Answer

I did this once. It was a huge headache dealing with the contractors. The only way I would no it again would be to have one of my crew pull the permits as a general contractor. Tie ins to the existing house are difficult to predict and quote until the house is torn apart, so a lot of contractors will not quote it, and the ones that do either quote it high to account for problems, or leave open ended clause in their contracts to compensate them for unknowns. You may or may not have to upgrade the entire existing house for electric, plumbing, and hvac. My guess would be $90,000, but that could easily be $150,000 if you can't control the contractors, or as low as $70,000 if you don't have to upgrade anything.

Jon Klaus · Answer

I did a very similar project 2 years ago for $92K. Added 800SF  master suite and additional bedroom. Also included rehabbing the existing 700SF home. We acted as GC and managed costs aggressively.  My partner on that project is great at keeping costs down.

Jon Holdman · Answer

Nearly impossible to give even a ballpark figure.  When I looked at a small addition, I was given numbers as high as $300 a square foot.  Your large addition will probably be less.  OTOH, you're talking about adding a bath.  Already have two?  If so, do you have a 4" drain line or 3".  Three baths requires 4" and changing that is a big expense by itself.  You'll likely have to bring affected areas of the house up to all current codes, so the work won't be limited to just the addition.

Does this even make sense to do?  You're doubleing the size of the house.  Does that make it oversized for the area?  Can you add the addition without it looking like a scabbed on mess?  Can you conform with zoning?

You need to get some contractors, and really an architect, to work up some plans and then start getting bids.  Multiple bids is essential, as prices will vary quite a bit.

Robert Leonard · Answer

This is not a good question for the nationwide audience to try to answer - you need to get an estimate from a Colorado contractor or active experienced rehabber based on your plan.  The current amount of building activity in your local market will determine the cost of construction.  I would call this an addition rather than a rehab, it sounds like a pretty dramatic improvement.

Derek Turbacuski · Answer

I was once told $100/SQFT to $125/SQFT  for new construction. Might be a little high for your purpose but a place to start. Better to overestimate. Get contractors to bid on construction portion.  Pricing the finish work you can do by walking around Home Depot/lowes.

Darrell Shepherd · Answer

There are a million "what ifs" on this...If I were forced to throw a number out I'd say $80/ft, but that could change a lot depending on how nice you make the kitchen and bath and what you have to do for the foundation, not to mention who you use to do it, going rates in your area, etc.