Everyone enjoys having friends, or at least friendly faces, at work. They make for good lunchtime company and honest thought partners. As a leader, it's natural to be concerned that friends at work can cause distractions. But according to recent research, having friends at work actually improves employee performance, making them more motivated and focused.

Good leaders not only encourage friendships among employees, but also help facilitate them. Here are four ways leaders have effectively built cultures of friendship at their respective companies.

1. Make friendship a company value

For Zappos CEO Tony Hsieh, the biggest priority is company culture. Building and maintaining culture started with establishing values that would operate as foundational pillars for the company. One of these values is "work-life integration." This means being yourself--whoever you are at home--at work as well. When people are comfortable being themselves at work, they form true friendships with colleagues. According to Hsieh, it's these friendships that have driven (and continue to drive) employee passion and company growth. Take some time to reflect on the values that define your organization's culture. If they don't already, consider how they could either explicitly or implicitly encourage healthy relationships between employees.

2. Support team-building activities

When employees are able to spend time together and have conversations that are not related to work, they are able to form bonds and find commonalities that, in turn, enable them to work better together. For instance, at Dropbox in hilly San Francisco, programmer Dan Wheeler's pastime has turned into a company institution. Dubbed "hillcore," it's essentially a "belief that you can get a group of friends and co-workers together, and climb a hill," Wheeler tells Fast Company. While people may talk or think about work while on their hike, this isn't the purpose. Rather, the purpose is to unwind. Whether it's climbing a hill or going bowling, plan and join unwinding activities for the team at least once a quarter.

3. Share company priorities broadly

Best-practice companies know that camaraderie is about more than just employee fun (which, of course, is important!). It is about aligning employees around a shared vision or purpose. This gives employees a sense that they are all in it together, both when things are going according to plan and when they are not. One way to establish this type of camaraderie is by broadly sharing company or team goals and encouraging employees to discuss goals with one another, even if they don't work directly together. This could come in the form of quarterly company all-hands meetings or more informal weekly or monthly lunch gatherings.

4. Establish rituals

Team or company-wide rituals bring people together and promote collaboration. At design firm Ideo, this comes in the form of Wednesday tea time. A few years ago, when the company's leadership saw that people were solely focused on getting their own work done, they realized that they needed to support behaviors of collaboration in order to spark creativity. Now, every Wednesday at 3 p.m., a bell rings and everyone comes out of their individual or smaller team spaces to gather in the kitchen for tea and a snack. This ritual encourages people who don't typically work together to engage with one another, thus deepening and strengthening their bonds with fellow employees.

From values to rituals, think about establishing the ways that employees can strengthen their bonds with one another. In turn, this will strengthen their bond with your organization.