Common strategies used to direct water away from building foundations

 Common strategies used to direct water away from building foundations

#Rainwater and #snow-melt that do not drain away from a #foundation and into a #drainage system will seep into the soil next to the foundation. If the water cannot percolate downward quickly through the soil to a level below the footings, the soil can become saturated and can even create #hydrostatic pressure against the foundation and beneath the floor. This can cause leakage into the #basement or crawl space.

#crawlspace

Quoted from Illustrated Users' Guide -- NBC2015

9.13.3.1. Required Waterproofing

 9.13.3.1. Required Waterproofing

Where #hydrostatic pressure occurs, assemblies separating interior space from the ground must be #waterproofed. #Roofs of underground structures must also be waterproofed. 

Hydrostatic pressure occurs when the #groundwater table rises above building assemblies. #Drainage systems, which are required around the base of #footings, eliminate hydrostatic pressure on the assemblies above as long as the footings are below the water table. However, footing drains can become ineffective if they are blocked or have an inadequate capacity. Certain sites tend to be wet and poorly drained because of #topography or soil conditions; as a result, when #snow melts or during periods of heavy rain, below-grade spaces may be subjected to hydrostatic pressure. #Walls and #floors subject to hydrostatic pressure from a high water table must be designed to resist such pressure.

Quoted from Illustrated Users' Guide - NBC2015

9.13.2.5. Moisture Protection for Interior Finishes

 9.13.2.5. Moisture Protection for Interior Finishes 

Excess water from #cast-in-place #concrete and ground moisture tends to migrate toward interior spaces, particularly in the spring and summer. Where moisture-susceptible materials, such as #finishes or #wood members, are in contact with #foundation walls, the moisture needs to be controlled by installing a moisture barrier on the interior surface of the foundation wall that extends from the underside of the interior finish up the face of the wall to a point just above the level of the ground outside. 

The reason the moisture barrier on the interior surface of the foundation wall must be stopped near ground level is to allow any moisture that finds its way into the finished wall #cavity from the interior space (through leaks in the air or vapour barrier) to diffuse to the exterior. If the vapour #permeance of #dampproofing membranes or coatings exceeds 170 ng/(Pa·s·m2) (3 perm), the moisture barrier may be carried full height. If their #vapour #permeance is less than 170 ng/(Pa·s·m2) (3 perm), there is a risk of #moisture being trapped on the interior surface of the moisture barrier. The permeance limit corresponds to the lower limit for breathable building membranes, such as asphalt-impregnated #sheathing paper.

 

Quoted from Illustrated Users' Guide - NBC2015

#moisturebarrier #foundationwall #interiorfinish #sheathingpaper

9.13.2.4. Application of Dampproofing Material

 9.13.2.4. Application of Dampproofing Material 

1) Exterior #dampproofing shall be applied from finished #ground level to the top of the exterior of the #footing. 

2) Unless otherwise stated in this Subsection, dampproofing shall be installed in accordance with the manufacturer’s instructions with regard to

 

a) surface #priming, 

b) conditions during application, 

c) application quantity and rate, and 

d) #curing times. 

3) #Joints, #cracks and #penetrations shall be sealed to maintain the continuity of the dampproofing, where the dampproofing material is not capable of bridging such discontinuities.

Quoted from Illustrated Users' Guide -- National Building Code 2015