Footings Flashcards
What problems may be encountered if the excavation ramp is dug under a future driveway at the end of the house?
Cracked concrete concrete, pulling away from the house the driveway tilting
How should unstable soil be excavated?
Add a 45° slope or 600 mm
How should stable soils be excavated?
600 mm vertical with working room straight
Where should excavated material be stored?
1000 mm from the edge of excavation or 1 m back
Using the NBC, what is the minimum depth of foundations in clay? Soil’s good drainage containing a heated basement
1.2 m from NBC 9.12.2.2
What is the minimum depth of the foundation in well-drained clay soils, containing an unheated crawlspace?
1.2 m not less than the depth of frost penetration
Backfill that is within 600 mm of a foundation shall be free of
Deleterious debris and boulders, larger than 250 mm
Using the NBC, what is the minimum amount of the foundation must extend above the finished grade
Not less than 150 mm above finished ground level
Topsoil and vegetable matter need to be removed under a building
Tru
Excavations should be kept free of standing water
True
The bottom of excavations should be kept from freezing throughout the construction period
True
Dewatering
A series of well points drilled around the perimeter pumps are used to continuously remove the water from that area
Excavating machines that could be used to excavate a basement for a house
Crawler loader, skid steer, wheel loader
The depth of an excavation for a house, depends on several factors, such as
Surface drainage, elevation of the street, sewer and water
There are several types of spread footings
Continuous footings, independent footings, and raft footings
Continuous footing
Unbroken footings extended throughout the perimeter of the building
Stepped footings
Continuous footing stepped up or down to accommodate different elevations in foundations
Pilaster footings
Continuous footings that are widened under areas were extra loads are placed on the footings such as under fireplaces. These are also referred to as offset footings.
Bearing wall footings
Regular continuous footings with raised centre portion
Independent footings
Support, Tele, post, columns and peers. There are three types of independent footings.
Independent footing pad
A square or rectangle or flat footing
Independent, battered footings
Have flat tops and bottoms, but tapered sides used to support a load that requires only a small support area and are widened at the bottom to give enough bearing
Independent stepped pad footings
Have the centre portion, increased, and thickness to provide extra support for a column
Raft footing, or Matt foundations
A solid slab of heavily reinforced concrete covering the entire building location slabs may be from 620 400 mm thick are used to support the building. The raft footing also known as floating slab is often used as the foundation floor of detached building such as garage
Tolerance for footing width
15 mm under and no more than 2.5% of footing with over
Tolerance for footing off-center
No more than 5% of footing width off
Tolerance for footing reduction of thickness
5% under no limit in over thickness
Tolerance for footings, elevation
Maybe 3 mm over or under
What is the purpose of a spread footing under a foundation wall?
Enlargement or wedding under a foundation wall to distribute the weight of the building over a large area that’s preventing settling
And unreinforced footings, the projection of a footing beyond the supported element should not exceed
Thickness of footing in NBC, 9.15.3.8
The maximum height of a stepped footing is
600mm
Using stepped footings, the minimum length of each steps should be
600mm
When using step footings, the thickness of the vertical connection should be
150mm
The minimum thickness of footings allowed by the NBC is
Not less than or greater of 100 mm or width of the projection of the footing beyond the supported element
The minimum width of footings under an exterior basement wall supporting one floor bungalow is
209 nbc 9.15.3.4
The minimum area of a column footing is
.04
If the footings rest on gravel, sand, silt, or clay, and there is Highwater table present, the footing with should be
Not less than twice the width initially stated NBC 9.15.3.4.3
If a brick veneer is added to the front of the house, what must be done to the footing under the brick?
Wall thickness may have to be increased an adjustment of 65 mm
Concrete for unreinforced footings she’ll have a minimum compressive strength of
15 mpa
Footings may rest on undisturbed soil, rock, or compacted
Granular fill NBC 9.15.3.2
Two methods of anchoring, a foundation wall to a footing are
Rebar dowels, or a keyway
What tool is usually used to set footing forms to the proper elevation?
A builders level, a laser or a transit
Why may footing forms be lapped at joints instead of putting the material together?
Saves time and materials and a stronger
Which footing forms are usually installed first inside or outside and why?
Outside and continuous footing throughout the perimeter of the building
One plumbing down from a string line on the batter boards to the bottom of the excavation, when is a straight edge and hand level more suitable than a plumbob
Windy conditions
When using a 2 x 6 ( 38X140mm) material for footing forms how Far apart should the 2 x 4 (38 x 89 mm) Steaks be placed
3 feet or 1 m
Why should the tops of the steak supporting the forms to be driven down or cut off flush with the tops of the forms?
For placing and screeding concrete or striking off
