Know-How Exchange : Taglines/Names

Ask your client's customers why they chose them and how they refer the company to their friends.

The "high standards" (etc.) are assumed. What results are visible? Are estimates never exceeded? Are move-in dates in writing? Is all work warrantied for 10 years? Are change orders free? Unearth the specific benefits they provide first.

I assume the world knows your company is family owned.
Family owned - Our name is on every job...

Welcome to our Family
Like Having an Uncle in the Business
Family Builders
Our Name is On Your Door
You're More than a Client- You're Family

I have some comments and questions for you.
You say that they think they make the process as smooth as possible. Do you know what their customers think? As smooth as possible is very vague. What if their competitors make it lot more smooth because they have more capabilities then your client.
Have your client every surveyed their customers to learn what and how are they doing in their customers eyes. Their client can think all they want to, but it is what the customers think that matters
What is a Brand? Perception of the product or service. Being nice is not enough as your product needs to stand up to customers expectations. In the business your client is in, it is a very involved product and a service. They have to deliver on everything and all the way for their customers to experience a positive feeling about your client’s brand.
Then you say that you are trying to define their brand in a way that truly distinguishes them from competitors and they would like their brand to represent trust, quality and comfort throughout the entire process. A tagline simply can’t create a brand. The product/service has to deliver and the final product creates the brand. So my suggestion would be first to go back to survey your client’s customers. That survey done right will give you a picture of what your client’s customers think of them. You or your client needs to see what their competition is doing and how are they doing and part of the survey should be to compare your client to their competitors on a rating scale and then probe for where their competition is doing better
Then you may be able to come up with a tagline.Remeber all the taglines will not make a difference if you don’t deliver what the customers are asking for. Big part of the business your client is in also in their creativity and then not only tagline will be needed, but pictures of their creative work. I would imagine that lot of their advertising will be in print and there examples of your creative work will speak volumes rather than a tagline.
Good luck

Perfection Can Be Designed.