carpentry 1- conventional concrete foundations
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list 2 methods or systems used for residential modular wall forming.
- 1. flat bar system
- 2. patented panels (pre-manufactured)
list the 6 basic components of the flat bar system.
- 1. plywood panels
- 2. form ties
- 3. flat bars or waler bars
- 4. corner hardware
- 5. kickers
- 6. ribbons and bracing
when using the flat-bar system what must be done to the plywood panels to allow for the form ties?
slots to receive the form ties must be cut or routed
describe 2 desired features of a form tie.
- 1. keep 2 forms apart at the required thickness
- 2. help hold the forms together during placement of concrete
list the 2 types of corner hardware available for flat bar systems.
- 1. large steel brackets
- 2. hinges and rods
what is the purpose of a kicker?
accurately align the forms to the layout lines, keep the forms positioned during concrete placement, they tie the forms together at the bottom of the wall
after you have located the outside corners of the building and marked these points on the footing, what must be done prior to attaching the kickers?
double check all dimensions for accuracy and insure it is square, measure thickness of foundation wall, snap a series of chalk lines on the footings around the perimeter to indicate where the kicker is to be fastened
what is the sequence for erecting form panels?
begin from the corners making sure they are level and plumb and work to the middle
what is the next step after the initial forms are erected, braced and aligned?
begin inserting form ties and waler bars
how should bracing be installed?
the top of the brace is attached to the ribbon and the bottom is attached to the stake pounded in the ground, most effective if angle is 45 deg. or less and securely fastened in upper 1/3 of the wall
what is applied to the form panels to assist in removal of the forms?
form oil or a release agent should be applied to the forms prior to erecting the panels
how many nails should be used to fasten the vertical edge of the plywood panels at an inside corner?
a minimum amount of nails because they have weak holding power and damage the ends of the plywood end grain
what is the purpose of the latches on pre manufactured panels?
latches are used to hold the form ties in place and lock the panels together
how are corners formed with a pre manufactured system?
specially manufactured metal corner sections
steel reinforcement may be placed in concrete foundation walls to counteract what kind of stress?
resist lateral forces/stresses
list the minimum diameter , depth and maximum on center spacing of anchor bolts used to fasten a floor frame the the foundation wall.
hooked anchor bolts 12 mm minimum thickness, embedded at least 100 mm into concrete, start no more than 1200mm from the corner, and a spacing of no more than 2400mm
name 2 methods of anchoring the floor to the foundation wall.
- 1. anchor bolts
- 2. cast in place ladders
where is the greatest pressure on formwork during concrete placement?
internal (lateral) pressure to the forms at the bottom
list 4 factors that affect lateral pressure on forms when placing concrete.
- 1. rate of placement- vertical distance of concrete placed per hour into forms
- 2. outside temperature- as temperature increases concrete sets faster and visa versa
- 3. slump- high slump has more pressure
- 4. vibration- increases pressure by 20-30%
what should be done to the forms before concrete is placed in them?
ensure all snow, mud, sawdust and debris are removed from forms
list 2 reasons why concrete should not be dropped from a great height into the forms.
- 1. cause tremendous pressure on forms
- 2. separation of the aggregates which weakens the foundation
when using the flat-bar system, what must be done before removing the form panels?
the ties must be broken and the waler bars taken off. after the concrete has hardened, break the ties by striking the waler bars with a hammer
when removing the forms, care must be taken to not damage the forms panels or the new concrete. what precaution should be used in regards to the cast in place ladder?
use caution not to apply undue pressure to the ladders while stripping the forms. if the concrete is very fresh and the ladder is forced laterally it can break loose from the foundation wall and become useless
how are the form panels released using the pre manufactured panel system?
remove by raising the latches
what is the name of the pressure created by moisture in the soil?
hydrostatic pressure against the foundation
how are residential foundations normally damp-proofed?
by applying heavy coat of bituminous material such as ashpalt
what is used to provide a below grade drainage for foundations?
describe how weeping tile is installed.
by laying it next to the footing around the perimeter of the building. the top of the weeping tile should be below the top of the footing, with t he holes in the pipe facing down. the weeping tile must then be covered with at least 150mm of clean, course gravel
why should large machines not be used to backfill foundations?
they are heavy and compact the soul which will place great lateral pressure on the foundation
why should large rocks and lumps not be used in back-filling?
they can damage the damp proofing, they also create voids causing settlement later on
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