Tempo:
of concrete, ICFs, concrete masonry units or preserved wood. Since the inside grade is seldom much lower than the outside grade, the thickness of the foundation walls may be less than those enclosing a basement. Crawl space insulation, which can be installed either at the perimeter of the foundation or in the floor framing under the living space, is discussed in Chapter 5.
Crawl Space Ventilation and Ground Cover Crawl space walls below the level of the outside finished grade must be dampproofed. Install drain pipe around the footings and connect it to a sewer, ditch or dry well. Slope crawl space floors and access trenches toward the floor drain. For unheated crawl spaces, install a ground cover of concrete, asphalt or 0.15 mm (6 mil) polyethylene or Type S roll roofing over the ground surface with the joints lapped at least 100 mm (4 in.). For heated crawl spaces, install a 0.15 mm (6 mil) polyethylene sheet with joints lapped at least 300 mm (12 in.), sealed and weighted down, or, covered with at least 50 mm (2 in.) of concrete. The ground cover prevents ground moisture from entering the crawl space area. The crawl space must be conditioned like the remainder of the house, or ventilated (see Chapter 20), in which case the floor above must be insulated and be provided an adequate air barrier system and vapour barrier.
FOUNDATIONS FOR DECKS AND CONCRETE STEPS Frost action can cause supports for exterior decks, balconies and stairs to shift. Movement can cause structural damage and may allow water to drain towards the house. For this reason, balconies
with roofs, concrete steps with more than three risers, and decks more than 600 mm (2 ft.) above the ground require their supports to be founded on rock, on coarse-grained soil with good drainage, or, for other types of soils, the supports must extend below the frost line (Figure 175 on p. 253).
GARAGE FOUNDATIONS Foundations for garages are usually concrete or masonry. Concrete slab-on-ground or preserved wood foundations are also options. The minimum depth below grade for a garage foundation attached to a house should not be less than that shown in Table 3 (p. 264). If fill is required below the floor, use compacted granular material to avoid settlement after the floor is placed and loads applied. The concrete floor should be at least 75 mm (3 in.) thick. Provide an airtight curb or partition at least 50 mm (2 in.) high at the edges of the slab adjacent to interior space, and slope the garage floor to the outdoors. Place and cure concrete garage floors the same way as basement floor slabs. Provide control joints so that the concrete segments are similar in size. For a single car garage, one control joint dividing the floor into two roughly square segments should be sufficient. The foundation walls should not be less than 150 mm (6 in.) thick and should extend at least 150 mm (6 in.) above grade. Sill plates should be anchored to the foundation wall or slab with anchor bolts spaced not more than 2.4 m (8 ft.) apart and with at least two bolts in each sill piece. Extra anchors may be required at the side of the main door and in areas with high earthquake or wind exposure.
Crawl Space Ventilation and Ground Cover Crawl space walls below the level of the outside finished grade must be dampproofed. Install drain pipe around the footings and connect it to a sewer, ditch or dry well. Slope crawl space floors and access trenches toward the floor drain. For unheated crawl spaces, install a ground cover of concrete, asphalt or 0.15 mm (6 mil) polyethylene or Type S roll roofing over the ground surface with the joints lapped at least 100 mm (4 in.). For heated crawl spaces, install a 0.15 mm (6 mil) polyethylene sheet with joints lapped at least 300 mm (12 in.), sealed and weighted down, or, covered with at least 50 mm (2 in.) of concrete. The ground cover prevents ground moisture from entering the crawl space area. The crawl space must be conditioned like the remainder of the house, or ventilated (see Chapter 20), in which case the floor above must be insulated and be provided an adequate air barrier system and vapour barrier.
FOUNDATIONS FOR DECKS AND CONCRETE STEPS Frost action can cause supports for exterior decks, balconies and stairs to shift. Movement can cause structural damage and may allow water to drain towards the house. For this reason, balconies
with roofs, concrete steps with more than three risers, and decks more than 600 mm (2 ft.) above the ground require their supports to be founded on rock, on coarse-grained soil with good drainage, or, for other types of soils, the supports must extend below the frost line (Figure 175 on p. 253).
GARAGE FOUNDATIONS Foundations for garages are usually concrete or masonry. Concrete slab-on-ground or preserved wood foundations are also options. The minimum depth below grade for a garage foundation attached to a house should not be less than that shown in Table 3 (p. 264). If fill is required below the floor, use compacted granular material to avoid settlement after the floor is placed and loads applied. The concrete floor should be at least 75 mm (3 in.) thick. Provide an airtight curb or partition at least 50 mm (2 in.) high at the edges of the slab adjacent to interior space, and slope the garage floor to the outdoors. Place and cure concrete garage floors the same way as basement floor slabs. Provide control joints so that the concrete segments are similar in size. For a single car garage, one control joint dividing the floor into two roughly square segments should be sufficient. The foundation walls should not be less than 150 mm (6 in.) thick and should extend at least 150 mm (6 in.) above grade. Sill plates should be anchored to the foundation wall or slab with anchor bolts spaced not more than 2.4 m (8 ft.) apart and with at least two bolts in each sill piece. Extra anchors may be required at the side of the main door and in areas with high earthquake or wind exposure.
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