Architects and designers know how to design....right?

Yes.  That's why this discussion is so important.   Almost all firms start out by accepting any and all projects that walk through the door.  However, after a few years they begin to self-edit design services offered based on their experience.  That is a great idea.  For most practitioners, intimate project knowledge and experience is exactly what their clients are looking for.  In fact, the project will benefit from seasoned expertise and will likely be more successful. And the fees are better with experience.

Many young practitioners may not realize that carefully building their design practice around fewer project types may be a great way to establish expertise and recognition in this most noble profession.  Generally, clients like to hire seasoned experts - much like we all do when we seek professional help.  If possible clients prefer to hire firms with specific knowledge of the type of work needed and not a generalist who "could" do the work, but will have a vertical learning curve.  Here are some elements of design expertise that can be analyzed for your firm.

Portfolio and Expertise Review -  A "fresh eyes" review of your portfolio and resume background can be used as a method of proposing the best design experience to project to clients.

Experience Evaluation - With a clear understand of where the firm's experience lies, it can be broken down into "could", "can" and "should" design projects as marketing priorities.

Clarify design direction - It's important to choose directions that make both experience and financial sense for the firm.  Select practice directions that you enjoy, your firm excels at, and those that contribute to the bottom line.

Positioning of Marketing Collateral - Take a look at existing marketing materials like web, social media and project sheets to see how these elements can be used and distributed to position the firm as expert in the selected design fields.  Chasing two rabbits often means loosing both, so pick your expertise and target the best work for you.

Building Knowledge Library - Through a detailed interview and research process, document your design knowledge, key client issues, lessons learned, code issues, practical budget drivers, and begin to publish this knowledge in the form of white papers, eBlasts and blog posts on web and social media that use this new direction as the voice of the firm..

Is it possible to build a firm that can effectively tackle multiple project types?

Yes, but it is a rare client that places his bet on a designer that simply changes hats to announce his alternate expertise.  Rather an alternate expert is presented from within the firm .  In my experience the best of these practices are in fact an assemblage of smaller practices each with their own expertise and led by experts but grouped together under a single company banner. 

Let's examine your portfolio and the depth and breadth of your expertise.

While some of this seems rudimentary, to many firms there is hesitation to turn down clients or to publically suggest that the firm has any focus that would preclude other project types.  Unless a client is naïve or has some altruistic ideas, they are likely not to hire a firm for a project type they have never designed before.  A savvy firm can build on such tendency and position their design expertise in a manner to attract new clients and new work to their practice.  There is considerable overlap between Design Management and Marketing.  With your position clarified, together we can develop the best course of action.