We're just about to start a similar project in close-in DC suburbs. Our architect advised us to get preliminary estimates but we had trouble getting good numbers based on initial drawings. One contractor leveled with us and said they hate doing this - it can be tough to give a ballpark that's accurate and then if the bid comes out differently than the preliminary estimate, homeowners feel like they've been duped. I sort of sympathized with this since I had this experience even in early discussions with another contractor. In the end, in part because I was too busy to chase people and thought I had enough info to proceed, we had the architect proceed w/construction drawings and then went out for full bids.

Not surprisingly the bids were a lot more than our going-in assumptions! We're adding approx 500sqft above an existing addition for a master suite, gutting 2 existing full baths, adding a fireplace, replacing all windows and doors, and opening up part of the first floor. No change to stairs or foundation. We got 4 bids that ranged from $320k to $475k, exclusive of fixtures, tiles, cabinets, shower glass, etc. Demo starts next week!

"We aren't sure how to guide him (cut this, keep this) because it's hard to get a grasp on cost."

The builder is in the same boat. How does he know what to price from incomplete scope, drawings and specs.

The accuracy of any construction cost estimate is a function of both the quality of the information provided in the plans/specs (which is, by definition, limited for a concept or preliminary set of plans) and the quality of the effort by the contractor(s) producing the estimate. If there is an expectation of a "free" estimate, you'll likely get what you paid for: a back-of-the-envelope or similar quality estimate. Plus, most contractors know that homeowners typically select their builder on price, so guessing low in a preliminary estimate is often rewarded, albeit accompanied by a litany of excuses when the final costing based on the complete plans and specifications is presented. It doesn't serve anyone well.

I suggest the better alternative is to retain a contractor to produce a line-item estimate and pay them for their professional services just as you would for your architect/designer. They may credit some or all of the fees against the construction contract amount if you move forward with them. If you don't, they haven't provided hours of free consulting that took time away from other clients, family, and other interests.

We had a slightly different challenge when we started planning for our new addition. It was a surprise to me how complete the planning documents had to be before I could nail down some of the key concepts and ensure the design was buildable.

Example - The city permit offices apparently get a lot of what-if questions from homeowners. They don't want to talk to you until you have a complete plan, so it was difficult to get firm answers about some design aspects. For example, you might have a height restriction that is based on distance from the property line, so the city permit office wants to see exactly how high the house will be (that means they may want an architect's plan, not a simple line drawing) and a survey (performed by a licensed surveyor) that shows exactly where the house will be placed. It paid off to have an architect who had worked with the city before and could develop a plan that fit all the local rules.

Bruce

Tanya:

Don't expect the contractor to provide this information for free please; your architect gave you nothing without being paid.

Joseph - We paid our architect an $1,800 down payment and will be paying him $4,000 in total for completed construction drawings. So he gave us nothing for free.

Bruce - Thanks! We submitted our plat of survey to the village before starting any drawings and figured out what zoning issues we had to deal with. Just like you we had height restrictions that we had to work with in for sure.

Everyone else - Thanks for the input. I do understand a little bit more how it's difficult for the builder to quote accurately. When I spoke with them today they said exactly that. So I think we are just going to have to take the risk of having the architect finish up the drawings as we would ideally like to see everything. Knowing that we might have to pay him to revise it if the cost end up being too high once it's quoted.

There are lots of threads here on houzz.com where the OP was surprised by the cost to construct the home after having paid a considerable sum to the designer/architect for plans. In many cases, the cost difference between the homeowner's budget and the quoted costs was too great to align by making modest changes to the design. Major surgery is typically required with the attendant emotional and financial costs. Getting your builder/remodeler on board from the outset and having them provide realtime cost information helps to avoid such an outcome.

As a point of clarification, a "quote" or "bid" is a builder or remodeler's offer to execute a project at a particular price. By contrast, an "estimate" is a (hopefully) good faith inference of what it is likely to cost to execute a project. The former requires fully detailed plans and specifications; the latter does not.

"Joseph - We paid our architect an $1,800 down payment and will be paying him $4,000 in total for completed construction drawings. So he gave us nothing for free."

Please reread my post. Of course your architect did nothing for free. Neither should your contractor. Thanks for making my point.

Thanks Charles - Sounds like I need to revise my language when I ask the contractor for insight. Using estimate vs quote.

You can also sometimes pay for a consultation from a builder rather than a bid or estimate. He can offer insight on areas that are probably more expensive than useful and vice versa.

My friends used this to get an initial guesstimate of what their construction could cost. I'm not sure how close it was, but it's a start.

https://www.houzz.com/magazine/breakthrough-budgeting-info-the-houzz-real-cost-finder-is-here-stsetivw-vs~13875690

All of this advice is so valuable and helpful, thank you!!