I was the owner/builder and we went about 20% over but it was more of an estimate than a solid budget. The main areas we went over on were flooring, tile work, cabinets, tops, and stone. Those areas just happen to be the ones my wife was very involved in choosing finish/materials.

We're a couple of weeks out and should be about 25% over. Most of that is in upgraded finishes and things we added once it became clear that we were not going to need much of our contingency fund. We are about 5-10% over on a bunch of little things (framing changes, some plumbing items, sewer repair, civil engineering plan etc. etc.). Our major finish upgrades are in trim work, cabinetry, flooring.

We aren't finished yet but it looks like we will be about 25% over. Why? Because our builder who helped us price things out is on crack...lol. Surely it's not our fault. ;)

We were over by 13% really only due to my overages :)

I love our appliances and outdoor hard scape. I ended up putting in rat proofing, better insulation, and window coverings. Don't forget the cost of window coverings and security system installs. Have fun w your build!

I ended up about 10% over too - mostly due to my own choices. There were a few other things that ran over too. I think we ended up needing more fill, and there was something about the driveway - but most of it was on things like picking better cabinets, upgrades in the bathroom, and granite, etc...

Make that three of us at approx +10% based on personal decisions along the way. Actually, less than 10%; probably more like 5-6%. I kept a tight reign on the extras!

People who anticipate and budget 20-25% cost overruns should probably work things a bit harder before signing a contract. That's a huge number, and suggests someone didn't do their homework ahead of time.

Thank you for the replies. It sounds about like I expected and I find that reassuring. Based on your experiences, it sounds like we should only go significantly over if we decide to upgrade certain items.

>>>People who anticipate and budget 20-25% cost overruns should probably work things a bit harder before signing a contract. That's a huge number, and suggests someone didn't do their homework ahead of time.

I think there might be differing views as to build budgets and contingency funds. In our case, our 25% contingency was a way to keep us well within what we wanted to spend. Said another way, I suppose our "real" budget was the $1.25X we had in our heads rather than the $X that we had on paper. Do other folks not plan that way? In other words, if you want to spend no more than $500K, wouldn't you budget $400K and be happy when you have $ left over (or spend it on extras)? Maybe we just have a skewed perspective.

I would have been 2% over, as I had a max draw set by the bank and they would only approve me if I proved I could build within that amount. The actual construction was just that mere 2% over (I was crazy with spreadsheets, and where I went over I'd find somewhere else to save). However, I met the man of my dreams during the process, we got engaged and decided that to splurge a little (we were also going from 1 income paying all the expenses to splitting the costs of home ownership), so we willingly went 15% over on some luxuries. That being said, we're getting married on our property next September and *really* wanted it finished and gorgeous for our guests. Our overages were things like finishing off our front porch, adding extra gravel to the driveway, finishing the basement (we need the extra sleep space for guests since there's no local hotels), and air conditioning the house. And even then, we were predictably within our expected overages.

People who anticipate and budget 20-25% cost overruns should probably work things a bit harder before signing a contract. That's a huge number, and suggests someone didn't do their homework ahead of time.

Not necessarily. For example, sitework can often run over if you are building a basement and don't know what you will find.

"Not necessarily. For example, sitework can often run over if you are building a basement and don't know what you will find."

Very true. We built a walk out basement (in the front of the house) into a hill. We had lived on the hill for 15 years before deciding to build 'the' house. They ended up having to go 10 ft below basement level to find solid ground, then had to fill and pack. Then the county decided our 'zoning' was incorrect and required us to build to '1 hour fire' specs which included a residential fire system, tempered glass everywhere, no open decking, double sheet-rock, etc... Then when I went to pay for the 'septic authorization' (county allowing us to use our existing septic system), they said they screwed up and we weren't in a secondary fire zone and our zoning was rural residential so we didn't need to do all the fire mitigation construction. We had the plans re-done to reflect all the fire requirements which we didn't need. The county clerk actually called my wife to apologize but they didn't send me a check for all the extra $$ I had spent prior to them 're-zoning' me for the 2nd time. We ended up @ about 30% over budget for a build that was supposed to be 120 days but went 375. We knew we were into it big-time so just did what ever we wanted and budget be damned. Our builder tried to recoup all of his over-runs also (kind of shadily), we only paid him for the ones we signed off on and parted ways on less than friendly terms.

about ten percent....largely self inflicted via adding more space on second floor (and less attic sq footage)

This is an interesting topic. I just calculated where we are at and was surprised that we are only at 1.3% over right now. That is from upgraded things here and there -- carriage type garage doors, stacked kitchen cabinets, stone countertops, plumbing fixtures, lighting fixtures, hardwood floors (from laminate) -- those sort of things. A part of that is also from surprises from the builder like additional fees for smooth walls, and choosing "non-standard" options (that we were not aware of int he beginning). We are at the framing stage right now, and we are expecting another 1.3% (hopefully) for other stuff that we are in the process of choosing right now like security system, surround sound upgrades, electrical stuff etc. It is worth mentioning though that we really try to stick with what we set as an overage budget for each area of the build. If we can't afford it, we move on. This is for a 5500 sqft home.

Perhaps my PoV is influenced by the fact that I was a purchasing professional in a former life. ;-P
I don't approach CapEx and other significant spends in a way that allows for a lot of variance. Know your costs, know the anticipated margins of your suppliers, and eliminate variables ahead of time. And by that mean, include the appropriate terms for exceptions in your contract before breaking ground.
I mean, I wouldn't head into a car dealer with a $30k budget and end up handing them $37.5k for a vehicle.

Bungalow, that completely makes sense. On the other hand, I don't view a house as something that is finished when you purchase it, as is a car. While the basics of our house were covered in the initial contract, I knew we would not be able to reach consensus on some things until later on and we'd want the flexibility to make adjustments. I suppose in a particular situation where there are things beyond one's knowledge and control -- such as unknown site conditions or family harmony -- it might be better to allow extra $$ for that!