Glencoe: 19 Flashcards
footings shapes are made by
pouring concrete into a form
Form:
any framework containing wet concrete.
Forms can be made from:
any combination of steel, lumber, plywood.
Common footing forms are made with
2 x 4 lumber and braced to prevent them from being spread apart by the wet concrete. These boards are called haunch boards.
Spreaders, or form brackets:
The boards that hold apart the sides of the forms.
What nails are lumber formwork often assembled with?
Duplex nails because they make disassembly easier later on
A X should be formed in the top of the footing
Keyway
What does a keyway do?
Lock the foundation walls to the footing. It prevents moisture from seeping between wall and the footing.
Keyway is usually X” wide and Y” deep because Z
3 1/2” wide and 1 1/2” deep because a 2x4 is used to form it.
After the rebar has been positioned and the footings have been poured:
the tops of the footings should be troweled smooth.
Other load bearing structures such as columns and chimneys must
also be supported by footings.
Pier are X from foundation
Pilaster are Y from foundation
Pier are separate from foundation
Pilaster is part of it
A footing for a pier can be
round or sqaure
A pier is:
A block of column of concrete separate from the main foundation.
What is a pier used for:
often used to support girder floor systems or exterior decks.
What is sometimes anchored in a pier:
A steel pin or metal bracket is anchored in a pier to secure a wood post.
A pedestal on the pier should be X” above the finished basement floor and at least Y” above the finished grade in crawl-space foundations
3”
12”
When steel posts are used they are sometimes set X
If a concrete column is poured on top of a footing, Y
directly on the footing and concrete floor is then poured around them.
rebar placed vertically in the footing will keep the column in position.
How do you estimate the total rebar needed for a footing?
- Identify the combined length of all the footings. Suppose a foundation measures 42’ by 24’. The total length of footings is 132. ((42 + 24) * 2)
- Determine the exact number of lineal feet of rebar. Multiply the number of bars by the length of the footings. If 132 L.F and two bars are required you will need 264 L.F of rebar (132 x 2bars)
- Add an amount for overlaps. Each length of rebar must overlap the connecting length by an amount determined by local codes. In most residential projects it is enough to add 10% to the total lineal footage. Example:
264 X 0.1 = 26.4;
264 + 26.4 = 290.4 - Rebar typically ocmes in lengths of 20ft. Divide the total lineal footage by 20. 290.4 / 20 = 14.52 rounded up to 15.
15 lengths of 20’ rebar will be needed.
Stepped footings:
Footings that step down the sloped site.
When should the vertical step be poured in a stepped footing?
At the same time as the rest of the footing.
If the foundation wall is built with a concrete block, the height of the step should:
be in multiples of 8” because this allows the height of a block with a standard 3/8” mortar joint.
Step footings are set for sloping lot min X” below grade
min 42 in below grade.
The bottom of a step footing is always placed on X
undisturbed soil below frost line.
Horizontal lines of step footing should be calculated so that X
the horizontal spacing of the block can be maintained across the step
The vertical step of a step footing should be at least X” thick and be the same width as the rest of the footing
6”
Limit the vertical step of a step footing to X’ in height
2’ because this results in a stronger wall and makes the finish grading much easier.
