The exterior walls of buildings provide comfortable and healthy indoor environments, needed to protect us from outdoor climate change.
Most serious wall problems are related to water in one way or another.
Buildings need to be efficient, durable, and economical with regard to investment, operation, and maintenance costs.
Increasing focus on sustainability, design, and construction have given rise to new and improved materials, technology, and energy use in buildings.
Water and moisture intrusion can enter wall systems in several different ways.
Water penetration and moisture intrusion have been and will continue to an issue in construction.
Rainwater can enter wall systems and cladding in several different ways.
It could be driven by wind, or it may enter by gravity, or by capillary action, or by surface tension, or by differential pressure movement.
A very large percentage of construction related lawsuits are filed due to water intrusion issues.
It is quite likely that this trend will continue.
Typically, lawsuits and problems arise as a result of the ignorance of understanding water and how to manage it both in the construction trades and the design community.
The lack of a skilled workforce and increasing pressures on designers for faster work for less money greatly impact the problem.
It is important to understand the physical ways moisture can penetrate a building envelope: o Gravity - Kinetic Energy - is the movement of rainwater down the face of the envelope or cladding surface, as well as over other sloped areas, into openings (such as cracks, holes, and flashing) encountered on the way down.
o Capillary Action (suction) - is the property where water will draw itself into permeable materials through small openings (such as cracks, joints, and small holes).
For instance water getting sucked into a small crack similar to sucking on a straw due to various forces of air movement.
o Surface tension is the property that causes water to cling and run on to the underside of horizontal or nearly horizontal surfaces.
o Differential Pressure Movement is when water or water vapor is driven in the direction of lower air pressure from high pressure.
For example, if a building has negative air (more air being exhausted than is being forced into it, it is considered to have negative pressure).
o Vapor Movement - through Diffusion and Air Transport.
Vapor and air moves from warm toward cold driven by thermal differences (air currents) as well as the amassing or concentration of absorbed liquid material.
Solar heating can take rain, heat it to vapor and drive it toward the interior space of a building.
How To Determine If Water Is Damaging A Wall System? Be alert for water damage to the surfaces and systems, although in many cases you will not be able to any damage.
If the siding is deteriorating, there is a good chance that there may be some damage behind it, However, in many cases,( i.
e.
metal or vinyl siding and synthetic stucco) the siding looks fine while the sheathing and the structural members lying behind the siding are deteriorating.
The ability of the system to dry often determines the amount of damage done to the cladding and the structure.
Wall systems with sidings with good drying potential, such as aluminum or vinyl, may be less likely to suffer damage than synthetic stucco, for example, which has poor drying potential.
When looking at the exterior surfaces of the building, look first at the cladding materials and determine if they are in good repair.
Secondly, try to determine how water might get into the wall system and whether there are any areas where you might reasonably suspect concealed damage.
Inspection of the building interior should be focused on vulnerable areas that were noticed outside.
In some instances the moisture getting into the building envelope will show up on the interior finishes.
However, damage to wall assemblies, doesn't always show up on the building interior, at least not in the early stages.
Paying attention to the drying potential of the cladding system installed.
Brick veneer systems with vented rain screens have good drying potential, whereas most stucco systems do not.
Coverings and materials placed too close to grade can have a destructive outcome.
The siding should be placed at least 4" to 8" above grade to protect the system and structure from moisture damage.
Visual inspection should reveal seeing some of the foundation above grade and below the siding.
Foundations are designed to withstand moisture in the soil.
People may not like the appearance of exposed foundation, but from a functional standpoint it is necessary.
Siding materials placed too close to the roof surfaces will also keep the materials constantly wet.
Siding materials should be kept a minimum of one to two inches above the roof surface.
Planters and gardens should not be built against the home or structure.
A raised planter with three sides and the building acting as the fourth side is a poor arrangement.
Siding materials are not designed to be in contact the earth.
Having planters against the structure can have grave implications for the buildings.
Raised planters close to the building should have four sides and should be set out at least two inches from the siding.
This is not a common detail, but it is a lot easier on the building.
Vines and ivy growing on buildings all tend to hold moisture against the structure and trim.
This also provides pest entry opportunities.
In severe case, depending upon the type of vines, root systems, or attachment nodes, can damage siding or enter building, often through trim areas, providing a direct path for moisture into the building.
What Is Needed To Protect a Building from Moisture Intrusion? Management of the forces that drive moisture to and through the building envelope.
Moisture comes in four forms - solid, liquid, vapor, and absorbed.
Moisture investigation is difficult because the moisture can change forms and the analyst must hunt down all clues.
Water kills buildings.
Think about the ways moisture can enter a building.