A Shared Building LEP exists when two or more congregations permanently share a building but do not become a single congregation, continuing to worship separately, particularly where Eucharistic celebrations are concerned.
This is always the case when the Roman Catholic Church is a partner but there are reasons for other congregations wishing to retain a separate worshipping life. (They could have similar ecclesiological reasons, eg if it is an Anglo-Catholic Anglican congregation, or the congregations may just not be ready to combine.) It is possible for LEPs to ‘overlap’ and a partner in a shared building LEP could well be single congregation LEP.
Documentation specifically relating to Shared Building LEPs is below. Other literature about shared buildings and more general documentation about LEPs is also relevant.
If you are trying to write an LEP constitution, help is available here.