Glencoe: 23 Flashcards
What may building codes where earthquakes and hazards are common require?
a Bond beam
Bond beam
(collar beam) a continuous course of reinforced concrete or reinforced lintel block often positioned as the top course of a wall
Where is a bond beam (collar beam) positioned
It is often positioned as the top course of a wall. Sometimes it is placed every fourth course in the wall to stiffen the wall.
Concrete flatwork
consists of flat, horizontal areas of concrete that are usually 5” or less in thickness.
Foundation slabs, basement floords, driveways, sidewalks
Generally installed by a subcontractor who specializes in this
Where is flatwork placed?
either directly on the ground or over compacted gravel of sand.
How long should concrete flatwork be maintained in forms?
until it is strong enough to hold shape without forms.
What must be done to a concrete flatwork after it has been placed?
The top surface must be finished by being smoothed, textured, or otherwise worked by hand or power tools.
Where is flatwork commonly used
residential houses without basements or crawl spaces.
In mild or warm climates, flatwork has these advantages:
Reduced excavation costs because little earth has to be removed
Extensive or complex formwork is not required
a concrete slab eliminates the need for a separate subfloor
construction costs are lower
concrete provides a solid base for concrete block walls which are sometimes used in warm climates as the exterior walls of the house
Foundation slab disadvantage:
Utilities must be planned carefully and roughed in in advance. Because changes are very difficult to make once slab has been placed.
Foundation of home must be deep enough so that
it rests on soil that is below the local frost depth
Frost depth:
(frost line or freezing depth) The depth in any climate below which the soil does not freeze. If moisture is below the foundation, it can actually lift the foundation when it freezes and expands.
Frost heave:
movement caused by expansion and contraction of moisture in soil
What type of soil is best for foundation design
Expansive soil is not good. This holds its moisture such as clay.
Free-draining soil such as high sand content are the best because they do not hold moisture.
Two types of foundation slabs:
Monolithic and independent
Monolithic (unified slab, thickened edge slab, turned down footing): Consists of a footing and a floor slab that are formed in one continuous pour. The perimeter is thicker than the main area and is reinforced with rebar.
Independent (ground support slab): House is supported by foundation walls that extend to solid bearing below frost line. The slab is then poured between the foundation walls. After the formwork has been removed, the slab can be placed.
