Introduction

Staying dry and out of the elements is the most basic principle that architecture must fulfill. And consequently water and temperature transmission are some of the harder things buildings and designs must deal with. Water can come from above ground through precipitation as well as through below ground, via moisture and the water table.

Moisture Protection Approach

Generally, the first floor of a building should be raised high enough so that the land can slope away from the building and create positive drainage away from the structure. Also, there should be a continuous waterproof membrane applied to the surface below the ground to prevent water penetration. Waterproof membranes must be continuous and penetrations by pipes at footings and other junctures may require waterstops.

• All important pieces of a building’s function (MEP) should be located above the water table.
• DFE (Design Flood Elevation) should be considered when designing buildings in urban environments.
• International Residential Code (IRC) Requires that grading be sloped away from the building no less than ½” per (12”) foot for at least 6’-0” from the exterior wall.
• Barrier vs Rainscreen façade approach

Moisture Prevention

The building’s design should be detailed in order to prevent and resist moisture from entering the building, and in the event it does, allow the moisture to mitigate back to the outside air.

Thermal Insulation

Depending on where the structure is located and its program, the building is also detailed to control the heat flow in and out of the building. This is achieved through insulation and must be detailed in the correct thickness, type, and location within the envelope. Learn more about R-Values here, and where the vapor barrier needs to be located.

Application Location

Moisture protection can be located in one of three locations (positive, negative, and blind side).

• Waterproofing can be installed in any of these three locations
• Damp Proofing is only installed on the positive side.

Damp Proofing

Damp Proofing: Control of moisture that is not under hydrostatic pressure. Hydrostatic pressure is the pressure exerted by fluid, so for example a boat hull is under hydrostatic pressure. Damp proofing typically refers to coatings used on slabs and foundations below grade to protect them from vapor diffusion, but not against standing water or water below the water table.

• Damp proofing should not be used on anything below the water table. Anything below the water table needs waterproofing.

Methods & Application

The coatings for damp proofing are always applied on the wet side (positive side) of the element. Typically done by roller, brush, spray or trowel.

• Admixtures to Concrete: Elements can be added to concrete to make it less permeable to water. These may reduce the strength of the concrete, but will help with water resistance.
  • Examples: Mineral oil, powdered iron, salts of fatty acids
• Bituminous Coatings: Asphalt or coal-tar pitch materials, typically applied to foundation and exposed walls. These coatings come in many colors and are applied either hot or cold, and the surface needs to be smooth.
  • Brushed or sprayed on, it will not seal cracks that develop after the coating is applied.
• Cementitious Coatings: Portland cement mortar applied over the surface of masonry or concrete foundation walls below grade. The mortar coatings are frequently applied to rough walls to smooth them out for other damp proofing materials to be installed over the surface. They are also used by themselves.
  • Iron is added to the mortar. As the iron oxidizes from exposure to oxygen, it expands and creates a tighter seal.
• Plastics: Silicone and polyurethane coatings are available, which are usually reserved for above-grade damp proofing locations. Sometimes may be used as waterproofing, but typically are better materials than plastic.
  • Silicone is able to be sprayed, painted, or rolled.

Waterproofing

Waterproof controlling of moisture and water that is subject to hydrostatic pressure. This can include protecting parts below the water table.

• Waterproofing generally is tougher than Damp Proofing because it deals with the hydrostatic pressure and therefore creates a need to create a continuous seal over walls, slabs, and joints in the structure.
• Any cracks in the waterproofing would mean the system is compromised.
• The waterproof membrane should extend below the lowest level of the building

Application Location

Waterproofing can be applied to any location (positive, negative, and blind side)

Positive Side (Wet Side) Waterproofing

The most common place to put the waterproofing. 

• Done after the element and construction is in place
• Example: Exterior of a foundation wall. Once the foundation wall is built, the exterior of the wall has waterproofing applied. After the waterproofing is cured, the wall gets backfilled in stages so that settling is done in stages.

Negative Side Waterproofing

Applied after the element is built and in place. This is on the side that is not exposed to water (interior of the building).

• Example: Interior side of a foundation wall

Blind Side Waterproofing

Named because it is applied/constructed before the element is built and constructed in place. This is common in locations where the excavation is in a limited footprint and there is not enough space to excavate around the outside of the foundation.

• Example: Placed along the lot line edge of an excavation prior to the concrete foundation wall being poured. Once the wall is poured there is no more access to this space. You have to make sure that the waterproofing is done well and perfect prior to pour.
• Most common in construction with difficult or challenging site conditions (cities), as well as below concrete slabs.

Basic Types of Waterproofing Materials

Material, Detailing, and Construction Notes

• Membranes and fluid-applied systems should be protected from damage during construction and backfilling operations by placing protection boards over the waterproofing prior to backfilling. The protection board may consist of asphalt-impregnated glass fiber mats, extruded polystyrene (XPS) rigid board insulation suitable for use below grade, or some other proprietary product with or without an integrated mat.
• Geotextile or drainage board may be placed against the wall insulation in order to relieve hydrostatic pressure, as required for the climatic zone and local code requirements.
• Waterproofing should extend up the building and connect to the building’s moisture barrier and facade flashing to create continuous protection.
• Waterproofing should be protected from the sun’s UV rays by flashing or another exterior facade cladding material. 

Sheet Membrane

Built-up layers of bituminous saturated felts similar to roofing. This includes hot or cold applied asphalt felts, or single-ply membranes of synthetic materials such as butyl, and other proprietary and synthetic products.

• Sheet membranes may be loosely applied and attached to nailing strips, but more effective systems are adhered to the foundation on the positive side.
• Membranes are typically reserved for waterproofing walls subject to hydrostatic pressure because their cost and the difficulty of applying them is not usually warranted for simple damp proofing needs.

Fluid-Applied Systems

Includes modified asphalts, urethanes, and other synthetics. These are applied in liquid form to provide a continuous, seamless membrane.

• Applied on the positive side.

Cementitious Systems

Consists of portland cement, sand, and some type of Waterproofing add agent. Most common is a system that includes metal oxides. 

• Can be applied either on the positive or negative side.
• Positive side is more effective
• Negative side application should only be used as a backup for positive side waterproofing.

Bentonite Systems

Bentonite clay inside kraft paper packages or plastic liners in panel form. The bentonite expands in the presence of moisture, thereby preventing water from getting past. These systems are often combined with geotextile fabrics and can be used as both blind side and positive side reinforcement.

Crystalline Systems

Uses a proprietary mix of chemicals. During concrete hydration, the mixture comes in contact with water and expands to fill the pores, capillaries, and micro-cracks in the concrete with a non-soluble crystalline formation. This process both waterproofs the concrete and provides protection from alkali aggregate reactions, chloride penetration and carbonation (the corrosive effect that softens the surface layers of concrete). 

• This process will keep happening even after the concrete has cured. This means that the concrete is self-healing  should new cracks develop. 
• This can be applied to the surface on either the positive or negative side and is applied by brushing or spraying.
• Can also be added to the concrete as an admixture at the batch plant.

Waterstop – Joints in Waterproofing

Because the waterproofing is used when hydrostatic pressure can be expected, any joints in waterproofing are a place of weakness and potential failure. The typical solution used is a waterstop.

Typically used in concrete walls or joints, waterstops are continuous extrusions of rubber or neoprene, often with a dumbbell or ribbed profile. Half of the waterstop is placed in the form during the first pour of concrete, and the other half is allowed to extend into the second pour.

• Waterstops are made for a variety of situations where different amounts of protection and expansion are expected.

Foundation drains (Sump Pump)

To relieve water pressure and carry away accumulated water that drains down a foundation wall, a drain pipe may be set in the gravel at the level of the footing or slightly below the basement slab. This helps eliminate or reduce hydrostatic pressure created by ground water, as well as minimize the potential for water penetration in below grade areas.

• Gravel at the base of a building (and surrounding these pipes) helps with drainage and reduces capillary action.
• A perforated pipe along the foundation perimeter helps water travel to the sump pit or out to sunlight. Positive drainage is needed for the pipe.
• Sump pump and drain tiles are especially important if heavy amounts of rainfall or water are expected in the building’s location.
• Gravel around the pipe should be separated from the backfill with a layer of geotextile fabric, which keeps sediment from clogging the gravel drainage system, while still allowing water to pass.

Weather and Water Barriers

The exterior enclosure of the building must protect against the weather such as rain and snow. Also, vapor, air infiltration, and temperature differences. The way a building is detailed and how the façade needs to work, is developed on several criteria. These criteria change where air, vapor, and water barriers should be located as well 

• The climatic zone of the building
• Individual microclimate of the building
• Environmental conditions required inside the building
• Type of structure and exposed cladding being used
• Expected building movement

Water Resistant Barrier (WRB) vs Weather Resistant Barrier (WRB).

Often used interchangeably (as they basically are the same thing), a “weather resistant barrier” offers protection against both water and air infiltration, while a “water resistant barrier” only protects against water penetration.

• Therefore, technically, a weather resistant barrier is a more robust/comprehensive level of protection against the elements compared to a water resistant barrier.
• A weather resistant barrier can also be called an, ‘air and water resistant barrier’. This addresses the fact that it resists both water and air.

Weather Resistant Barrier

A weather resistant barrier (WRB) is a material that protects a building’s exterior walls from weather damage. 

• Prevent water from entering the building while allowing water vapor to escape 
• Keep building materials dry, which reduces the risk of mold, mildew, and rot 
• Reduce air infiltration, which can lower utility costs 

Water Barrier

Water barriers are the first line of defense against water penetration into a building. Water barriers can include the exterior surface of walls, waterproof membranes within walls, roofing, below-grade waterproofing, drip edges and flashing. 

Water barriers are not continuous and therefore do not address air infiltration.

A proper water barrier stops water and attempts to shed as much of it away from the building as possible.