Did you know 95% of construction litigation is the result of water intrusion? Learn how to avoid these headaches.
THERMAL AND MOISTURE PROTECTION
MasterFormat – Division 07
- 95% of construction litigation is the result of water
- 90% of all water intrusion problems occur within 1% of the structure’s exterior surface area.
- 95% of all water leaks are attributable to causes other than material or system failures.
While individual waterproofing materials and systems continue to improve, no one is improving the necessary, and often critical, detailing that is required to transition from one building component to the next. Furthermore, we seem to move further away from the superior results achieved by applying basic waterproofing principles, such as maximizing roof slopes, to achieve desired aesthetic values instead. There is no reason that aesthetics cannot be fully integrated with sound waterproofing guidelines. It is up to the industry to acknowledge these shortcomings and to resolve water intrusion problems at the job site rather than in the courtroom.
How is the water penetrating into any structure?
The same way it has ever since we built structures!
3 conditions create water intrusion (WOW)
- Water is present at the outer face of the wall.
- There is an opening through which the water can pass.
- A force to drive the water through the opening.
We cannot do anything about the water (rain) and the wind, but we sure can do something about the opening.
If there is a breach, water will intrude by using the following forces:
- Natural gravity. Water washing down the face of a building directly into an
- Surface tension. Water adheres to the surface of an opening and travels inward along
- Capillary action. Water travels inward because its adhesion to the walls of an opening is stronger than the cohesive forces between the liquid molecules. This occurs in very porous
- Wind / air currents. The wind currents can create sufficient air pressure to force the water upward and over the
- Hydrostatic pressure. Pressure applied to the building envelope materials by various heights of water at
Solving Water Intrusion Problems Restoration or Remedial Waterproofing
Now that we know how the water is penetrating a structure, how can we stop it?
In restoration or remedial approaches to solving water intrusion, the following actions are vital:
- Inspection of damage and leakage. (Visual inspection and testing).
- Determination of
- Choice of systems for
- Waterproofing system
Prevention of water leaks has to include one of the three basic systems:
Understand that not all water penetration through the substrate results in leakage to interior spaces. Masonry surfaces absorb some water regularly, without creating interior leaks. The masonry is either large enough to absorb the penetrating water, or this water is collected and redirected back to the exterior by the use of Dampproofing systems. This is also true when it comes to mortar joints.
1. Barrier Systems
Barrier systems are, as their name implies, effective and complete barriers to water infiltration. They completely repel water under all expected conditions, including gravity and hydrostatic pressure.
Such barriers include all types of impermeable materials above and below grade such as: membranes, glass, or metal that will completely repel the water.
Barriers are the most important element to consider in the design phase of a waterproofing project.
Barrier Systems (continued)
The barriers are as much systems as they are materials. The function of the barriers is to prevent any water penetration into the substrates.
They include metal, glass, and composite materials such as sheet and liquid membranes for vertical and horizontal applications.
The most popular system today is the elastomeric, which is a waterproofing material with the ability to return to its original shape and size after substrate movement during expansion or contraction.
Elastomeric is used mainly as a remedial system, because the original barrier, such as the building paper, is no longer performing, or the original design or application was not adequate.
Elastomeric works the same way as your skin; it allows the flesh (substrate) to breathe but does not allow the water to penetrate.
In most cases, the original barrier is abandoned when the elastomeric coating is applied. It is an economically attractive option compared with the cost of removing the sacrificial materials and the building paper then reinstalling the barrier.
Elastomeric materials should not be considered as a technological breakthrough, but as an economical way to provide an alternate barrier. As the original barrier and diversion system are abandoned, the barrier is moved to the surface of the wall where transition joints are critical.
Barrier Systems (continued)
Water repellents should not be considered as a typical barrier for waterproofing purposes.
They penetrate the substrates, filling the pores. After curing, they remain as a solid material or shield that provides water repellency. They are identified as: acrylics, silanes, siloxanes or stereates, depending on their composition.
Which water repellent to use is a complex process, which cannot be covered in this handbook. I suggest that you refer to the SWRI “Clear Water Repellents for Above Grade Masonry and Horizontal Concrete Treatments Manual”. This publication will give you a complete understanding of water repellents and a clear comparison of products.
Here is an example of and option of water repellent use.
In my backyard, this Cherub was cleaned every spring and would turn green with mold every winter. In the summer of 2000, I cleaned it and applied a siloxane clear water
repellent to the left side, leaving the right side untreated. In April 2002 the difference was obvious.
Water repellents do not provide the unper- meability requirement to be considered an acceptable barrier.
Drainage systems are components that might permit some water absorption and some infiltration through the substrate but provide means to collect this water and divert it back out before it causes leakage.
They can also be prefabricated materials that facilitate the drainage of water away from the building envelope.
Drainage system for decks
Diversion actually redirects the water being forced against the building and diverts it before it infiltrates the substrate.
Diversion techniques include sloping of roofs, decks and balconies; vertical drainage mats, gutters and downspouts, flashings, windscreens, French drains, etc.
SYSTEM INCLUDING DIVERSION
Building facades usually contain combinations of these three systems; each preventing water infiltration at their locations.
However, if they are not properly transitioned into other components, leakage will occur.
Solving water intrusion problems
- Natural gravity
To avoid any water penetration, it is necessary to have:
- The proper barrier, without any breach so that the rain cannot penetrate at
- The proper sloping. (Minimum ¼” per foot.) A good example is the teepee; built of materials that are hardly waterproofed. The interior will remain dry because the design sheds the water off immediately. However, use the same material in a horizontal or minimally sloped area and water will penetrate the same material.
2. Surface tension
To solve this problem, it is necessary to:
- Install and maintain drip edges and flashings to break the momentum of the water and prevent it from clinging to the underside of the horizontal surfaces and continuing into the
- Provide and maintain sound mortar joints.
The most common mistakes in restoration are:
- Not repointing joints where
- Filling or omitting new drip edges when repairing or installing
Not replacing non-performing flashings or not installing new ones where
Above: window header and sill without drip edge
Below: window header and sill with drip edge
3. Wind / air currents
When wind is present in a rainstorm, envelopes or cladding become increasingly subject to water infiltration.
Besides the water being directly driven into the cladding by the wind currents, sufficient air pressure can cause hydrostatic pressure on the façade and force the water upward and over the components.
Again, proper flashings should be designed and used to prevent this phenomenon from causing water penetration into the structure.
The cleat will at the bottom prevents uplift of the system.
Flashing used to prevent water under pressure from entering.
The height of the flashing is determined by the expected maximum speed and wind pressure.
All too often the height is not adequate because of aesthetic conflicts.
This detail is too important to take a back seat to design consideration.
Capillary action happens in situations where water is absorbed by wicking action.
This will happen mostly with masonry and concrete at or below grade levels.
These materials have a natural high degree of minute void space within their composition. These minute voids actually create a capillary suction force that draws water into the substrate when standing water is present. This is similar to the action of a sponge laid in water and absorbing the water.
Ironically, materials that have large voids or are very porous are not susceptible to capillary action in buildings. For example, sand is often used as a fill below concrete slabs to prevent the concrete from drawing water from the soil through capillary action.
Compacted sand and Pea Gravel fill.
The best way to prevent capillary action is to install a good barrier. In this case the barrier can be a waterproofing membrane, waterstops and compacted sand and pea gravel fills.
Hydrostatic pressure is the pressure equivalent to that centered on a surface by a column of water of a given height. The height of water due to its weight creates pressure on the lower areas (referred to as hydrostatic pressure).
This pressure can be significant where the water table is near the surface or rises near the surface during heavy rainfalls.
Water under this pressure will seek out any breaches, especially areas of weakness (i.e. the terminations and transitions between components).
These below grade components need a much better waterproofing system than the same components above grade.
Hydrostatic Control System