When designing the building envelope, there are other
considerations, for instance, variations in architectural massing can break-up wind-driven
rain.á Slope horizontal surfaces to
avoid ponding water.á Water vapor can go through solid materials
like gypsum wallboard, masonry and concrete unless there is a fully sealed vapor barrier in its
way.á Material changes are a potential
problem.á Building materials expand and contract at different
rates.á Expansion joints move, by
design.á It is best to place them out of the weather.
At windows, doors and wall openings, problems usually
arise because of water infiltration between the window and the adjacent cladding or because water
is not allowed to drain properly.á
Openings around
penetrations into the building should be closed with an air water barrier from
the exterior and must
function without the need for sealant.