Guide
Design-build or architect plus contractor: which should you choose?
The short answer
It comes down to whether you want one firm answerable for both design and construction, or a designer who works only for you. The best-known study, from 2018, found design-build faster and steadier on cost and schedule, but it measured industrial, office, high-tech and multi-story residential buildings of 5,000 square feet and up, not houses. Under California law either route can deliver a house, an ADU or a remodel, and what the study recommends on any route, such as team chemistry and bringing a builder in early, is open to both.
The two routes, in plain terms
With an architect plus a contractor, often called design-bid-build, you hire a designer first and then take the finished drawings to builders for prices. You hold two contracts, one with the designer and one with the builder.
With design-build, you sign one contract with one firm for both the design and the construction, and that firm brings in the designers, engineers and trades it needs.
The research below also measures a third route, construction manager at risk, where you keep separate contracts with the designer and with a builder who manages construction.
What the research measured
In 1998 the Construction Industry Institute compared the three routes on more than 350 U.S. building projects finished in the mid-1990s, in a study by Victor Sanvido and Mark Konchar. As the authors of the later update summarize it, design-build came out ahead on unit cost, on cost and schedule growth, and on every speed measure. We could not open the 1998 paper itself, so we rely on that summary.
Twenty years later, Keith Molenaar and Bryan Franz repeated the study for the Charles Pankow Foundation and the Construction Industry Institute, using 212 projects completed between 2008 and 2013. Design-build again led. The cost gap between the routes had narrowed, while the speed gap had widened.
| Measure | Design-build against design-bid-build |
|---|---|
| Cost per square foot | 0.3% less |
| Cost growth during the project | 3.8% less |
| Schedule growth | 1.7% less |
| Construction speed, in square feet built per month | 36% faster |
| Delivery speed, from the start of design to completion | 102% faster |
Read the growth figures with care. The study's models explained almost all of the differences in unit cost and most of those in speed, but only about a fifth of the differences in cost growth and schedule growth.
The delivery route was not the only thing that mattered. Across the projects, the study tied better results to these conditions, and the authors recommend them whatever route an owner picks:
- Good team chemistry between the owner, the designer and the builder.
- Bringing the builder in early, and setting the project's goals together.
- Open-book contract terms, such as cost plus a fee under a maximum price agreed in advance.
The worst projects in the study had the opposite: managers new to the job or the method, poor communication between owner and builder, and people leaving the team midway.
Why those numbers may not carry over to your house
The 2018 sample was light and heavy industrial, office, high-tech and multi-story residential buildings, from 5,000 square feet to over a million, and 62 percent were publicly funded. None of its categories is a single-family house, and its smallest building is more than four times the 1,200 square feet the City of San Diego allows for a new ADU.
We looked for peer-reviewed research comparing the two routes on houses or home remodels and found none. Treat a precise saving quoted for a home project with care unless it names its sample.
What California law says about who designs and who builds
You do not always need a licensed architect for a house. State law lets anyone prepare plans for a single-family wood-frame house of up to two stories and a basement, for up to four such units, and for garages and other structures that go with them. Where any part departs from conventional wood framing, the building official will require that part to be drawn and stamped by a licensed architect or engineer.
A licensed contractor may design work inside that exemption, plus the systems needed for jobs it has contracted to build. Anything beyond that must be designed by or under a licensed architect or engineer, and a contractor without an architect's license may not call itself an architect.
Either way, you sign a written contract. An architect generally needs one before starting work, covering the services, the pay, how changes are handled and how either side can end it; the Architects Board lists a few exceptions, such as the client's written go-ahead. For all but the smallest jobs a contractor's home improvement contract must be in writing too, with a description of the work and the main materials, a schedule of progress payments tied to the work, approximate start and completion dates, change orders in writing and a three-day right to cancel.
The law caps a home improvement downpayment at 10 percent of the price or a fixed dollar limit, whichever is less, and makes it illegal to collect for work not yet done or materials not yet delivered.
When a job needs more than two trades, CSLB points you to a licensed B General Building contractor, who can contract for and oversee all of it.
How to choose
- Design-build may suit you if you want one contract and one party answerable for the design and the price, and you are comfortable that the designers work inside the firm that will build.
- An independent architect may suit you if you want a designer whose only client is you, or drawings you can take to several builders for prices.
- On either route, ask who holds each license, who stamps the structural work, and who pays when a drawing error costs money.
- Bring the builder in early whichever route you take; the 2018 study tied early involvement and shared goals to steadier cost and schedule.
- Check every contractor's license with CSLB before you sign.
What changes the answer
The cases where the law or the project decides part of this for you.
A building outside the wood-frame exemption
A building of more than two stories, or one that is not conventional wood framing, needs a licensed architect or engineer for its design, and any part of an exempt building that departs from conventional wood framing needs one for that part, on either route.
A pre-approved ADU plan
If you build from a plan your city has pre-approved, most of the design already exists. The choice shrinks to who prepares the site plan and who builds.
The Coastal Overlay Zone
In the City of San Diego's Coastal Overlay Zone most new ADUs also need a Coastal Development Permit, a review step that comes with either route.
A senior homeowner
For a senior citizen, as the law defines one, the right to cancel a home improvement contract runs five days instead of three.
A contractor with a blanket bond
A contractor with a blanket performance and payment bond on file with CSLB can ask for the full price up front, without the usual payment schedule. CSLB says few companies hold one, and the license lookup shows it.
Next steps
Decide what you are building, then how you want it designed.