If the number of people attending your church is growing beyond the available seating capacity, you could build a bigger church. However, an increasingly popular alternative being adopted by many churches is to become a multi-site church, and multi-site churches of many different flavours are discussed in a helpful Leadership Network Innovation Series book, The Multi-Site Church Revolution, by Geoff Surratt, Greg Ligon and Warren Bird.
There are many practical advantages to multi-site churches. It is far less expensive to have smaller buildings rather than larger buildings. It is much easier to find available real estate. With smaller congregations in each venue there are less likely to be major traffic jams. Local government zoning issues are less likely to be problematic, and relations with neighbours are likely to be better. Often existing buildings can be used without the need to build new ones.
Aside from the practical advantages of a multi-site strategy, many churches have found that a multi-site presence significantly enhances their mission. People are more likely to invite their neighbours if they can attend a venue which is near where they live. A new multi-site venue is like a church plant, but it has instant access to the reputation and resources of an established church. Any growing church should be considering the advantages of a multi-site strategy.