Planning, Laying Out, and Tooling Concrete Block

1
Lesson

• Planning, Laying Out, and Tooling Concrete Block

2
Student Learning Objectives

• Discuss how to plan and lay out a job.
• Explain how to mix mortar and lay blocks.
• Explain how to tool joints, patch holes, and
  clean smears.

3
Terminology

• Batter boards
• Block chisel
• Block hammer
• Block trowel
• Closure block
• Concrete masonry units
• Corner block
• Face shell mortar bed
• Frost line
• Full mortar bed
• Jointer
• Lightweight blocks

• Masons line
• Masonry cement
• Masonry sand
• Mortar
• Mortar hoe
• Raker joint
• Standard or heavyweight blocks
• Story or course pole
• Stretcher block
• Tooling joints

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Anticipated Problem

• How can I plan and lay out a concrete masonry job?

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Concrete masonry

• Popular type of agricultural construction.
• Concrete blocks are strong, durable, fireproof,
  rodent and termite proof, and do not rot
• Concrete masonry units, also called concrete
  blocks, come in two types and several standard
  sizes

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General Types

• Two general types
• hollow
• solid
• Standard or heavyweight block
• Made from Portland cement, water, sand, gravel,
  and crushed stone

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General Types

• Lightweight blocks
• Made from Portland cement, water, and lightweight
  aggregates, such as cinders, slag, or shale.
• Weighs half as much as a standard block
• Easier to handle but have greater insulating value

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Block Sizes

• Even number widths
• 4, 6, 8, 10, and 12 inches
• Even number heights
• 4 and 8 inches
• 8 8 16 block
• Widely used to build agricultural structures.
• Actual dimensions are 7 5 /8 7 5 /8 15 5 /8

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Block Sizes

• When the standard 3/8 mortar joint is added, the
  block with one mortar joint is 8 inches high and
  16 inches long.

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Pictures Courtesy of Interstate Publishers, Inc
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Block Types

• Building dimensions
• Total length and width in inches should be
  divisible by eight so that full blocks and half
  blocks will be used
• Blocks come in a variety of shapes
• Corner block and stretcher blocks are the most
  common

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Block Types

• Stretcher block has ribs on both ends
• Usually with three cores or holes in the block
• Used between the corners

Pictures Courtesy of Interstate Publishers, Inc
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Block Types

• Corner block Square across one end and has ribs
  on the other end
• Used at the corner when laying blocks Use the
  dimensions to figure the
• Use the dimensions to figure the number of blocks
  needed.

Pictures Courtesy of Interstate Publishers, Inc
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Other Blocks
Pictures Courtesy of Interstate Publishers, Inc
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Bonding Materials

• Mortar Bonding material made of sand and masonry
  cement
• Mix one part cement to 2½ to 3 parts masonry
  sand.
• Masonry cement Type of cement used to make
  mortar while Portland cement is used to make
  concrete

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Bonding Materials

• Masonry sand is fine sand while the sand used in
  concrete is coarse sand
• Use the following as a guide to calculate the
  amount of cement and sand to purchase
• in a 13 mix, 1 bag of cement and 250 pounds of
  sand will lay 100 eight inch blocks.

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Laying out the Structure

• Building must be laid out prior to digging the
  footing and pouring it
• Surveying instruments
• Easiest, quickest, most accurate way to lay out
  buildings corners
• Generally laid out parallel to property lines or
  other buildings

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Laying out the Structure

• Surveying level and target rod
• Helps to set square corners and the proper height
  of the foundation wall
• Dimensions should always be doubled checked
• Measuring for equal diagonals is a way to check
  for square corners.

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If no Surveying Equipment

• Establish a base line and use the 345 right
  triangle method to establish square corners

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Outer Supports

• Batter boards Outside supports used to stretch
  strings
• stretch strings set up when corner stakes are in
  place
• The batter board includes three stakes and two
  horizontal 1 x 4 or 1 x 6s
• The strings mark the outside of the foundation
  wall and the top of the foundation

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Outer Supports

• Plumb bobs can be helpful to insure that the
  strings intersect over the corner stake
• Use powdered lime or spray paint to mark the
  ground for digging the footing

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Outer Supports

• Remove strings while the digging is done.
• The surveying level and the target rod are used
  to set the grade stakes or forms in the trench

23
Outer Supports

• The footing trench should be dug down to firm
  soil below the frost line
• Frost line Deepest point in the soil where the
  ground freezes in a typical year
• The bottom of the trench should be flat and level

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Outer Supports

• Footing rules are
• Set at or below the frost line,
• pour a minimum of 8 inches for 8 inch blocks, 10
  inches for 10 inch blocks, etc., and
• have the footing at least twice as wide as the
  foundation.

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Outer Supports

• After footing is poured and forms are removed
• Sweep off the footing and re-stretch the strings
• The plumb bob can be used at the string
  intersection to help mark the corners on the
  footing

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Outer Supports

• Snap a chalk line on the concrete footing to mark
  the location of the outside of the first row of
  concrete blocks
• Beginning block layers sometimes lay out the
  first row of blocks without mortar to make sure
  the layout was planned properly

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Pictures Courtesy of Interstate Publishers, Inc
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Anticipated Problem

• How is mortar mixed and blocks laid?

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Mixing Mortar and Laying Blocks

• Good mortar Absolutely necessary for good
  workmanship and a good finished wall
• Process of laying concrete blocks requires
  considerable know-how and skill
• Concrete masonry work may be contracted to
  professionals

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Concrete Masonry

• You start by mixing mortar and carrying blocks
• Start with
• Clean, dry blocks
• water
• masonry sand
• masonry cement
• concrete blocks
• quality tools

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Mixing Mortar

• Strength of a mortar joint is affected by
• Quantity of cementing material,
• Portions and moisture content of the mortar, and
• Quality of the workmanship.

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Mixing Mortar

• Mix one part masonry cement to 2½ to 3 parts
  masonry sand with enough to make a workable mix
  that is plastic enough to support blocks on a 3
  /8 inch mortar joint until it has set
• If masonry cement is not available
• Use Combination of Portland cement and hydrated
  lime

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Mixing Mortar

• Mix mortar in
• A leakproof box with shallow sides,
• A wheelbarrow, or
• A mixing machine

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Mixing Mortar

• To hand mix
• Use a mortar hoe (a hoe with two large holes in
  the blade) to dry mix the cement and sand until a
  uniform color exists.
• Gradually add water and continue mixing with the
  mortar hoe until the mortar is plastic and
  workable

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Mixing Mortar

• If mortar is
• Too stiff Will not bond well and results in a
  thick joint
• Too thin Will be squeezed out by the weight of
  the block resulting in narrow mortar joints

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Pictures Courtesy of Interstate Publishers, Inc
37
Concrete Layout

• Locate the corners and lay out the first course,
  without mortar, to check the layout
• Full mortar bed Using mortar on both horizontal
  and vertical cross webs of the block
• Face shell mortar bed Using mortar on only the
  horizontal cross webs of the block

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Concrete Layout

• Normally the first course uses a full mortar bed
  and the other courses use a face shell mortar bed
• Always lay the blocks with the thicker end of the
  face shell up
• This provides a larger area on which to place the
  mortar

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Laying first course of Blocks

• Masons line Nylon string that is stretched
  tight to mark the top and outside edge of a row
  of concrete blocks
• Once the first course corner blocks are laid in
  position stretch it so that the first course will
  be straight
• Buttering refers to putting mortar on the end of
  a block

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Laying first course of Blocks

• Block layers often stand several blocks on end
  and butter the ends
• To get a better bond to the block
• Flip mortar off trowel onto block with snap of
  the wrist
• To place the block in position
• Pick it up with both hands and use a swinging
  motion to lower it into position

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Pictures Courtesy of Interstate Publishers, Inc
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Pictures Courtesy of Interstate Publishers, Inc
43
Laying first course of Blocks

• To make sure a laid block is level plumb, and
  aligned
• Use a level
• Level the blocks by tapping the block with the
  handle of the trowel

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Pictures Courtesy of Interstate Publishers, Inc
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Pictures Courtesy of Interstate Publishers, Inc
46
Laying first course of Blocks

• Block trowel Triangular shaped piece of metal
  with a wooden handle
• Block hammer Can be used to tap blocks into
  place as well as cutting blocks

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Laying first course of Blocks

• Block chisel Three or four inch wide metal
  chisel that can be hit with the block hammer to
  mark and cut concrete blocks

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After first course of blocks

• Use face shell mortar beds and lay up 4 or 5
  courses of blocks at the corners
• Check for each blocks
• Level, plumb, and alignment
• Checking horizontal spacing
• Use a straightedge or four foot level

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After first course of blocks

• Since each course is back spaced a half block,
  the corner of each back stepped row should touch
  the diagonally positioned straightedge.
• Story or course pole Board with markings eight
  inches apart
• Use to ensure that the horizontal mortar
  jointings are running 3 /8 inches thick.

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After first course of blocks

• Key to a straight true wall
• Using the masons line between the corners as a
  guide
• Most difficult part of laying blocks
• Usually laying the closure block

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After first course of blocks

• Closure block Last block laid to complete the
  row
• If vertical mortar joints have been 3/8 inches
  the opening for the last block should be 16 3/8
  inches long (2 3/8 inch mortar joints and a 15
  5/8 inch block)

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After first course of blocks

• Closure block
• Must be buttered on both ends or
• Previously laid block must be buttered
• If mortar falls off the end of the block as
  swung into place, block should be removed and
  re-buttered

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Anticipated Problem

• How are mortar joints tooled and smears removed?

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Tooling joints and removing smears

• Completes job resulting in a professional
  appearance to the job

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Tooling Joints

• Procedure that pushes the mortar into the groove
  between the blocks
• Creating an improved bond of the mortar to the
  block
• Results in a weather-tight joint with a neat
  appearance
• Jointer Concave or V-shaped metal tool with a
  handle and turned up ends

56
Tooling Joints

• Brick layers often use a raker joint.
• Raker joint Tool that moves the mortar from the
  joint to depth of approximately 3/8 inches

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Removing mortar burrs

• After joints have been tooled, trim off with
  face of the wall with the trowel

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Crooked Blocks

• Do not attempt to move or straighten the block
  once the mortar has stiffened or even partly
  stiffened

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Patching and Filling Joints and Holes

• Should be done with fresh mortar

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Mortar Dabs

• On block
• Should be allowed to dry
• Use trowel to knock dab off
• Piece of a concrete block to rub out remaining
  particles

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Smears

• When laying blocks, be careful not to smear
  mortar into the blocks
• Once the smears are in the block it is impossible
  to remove them
• Muriatic acid rinse will help clean the wall and
  make paint smears less noticeable

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Review / Summary

• Discuss how to plan and lay out a job.
• Explain how to mix mortar and lay blocks.
• Explain how to tool joints, patch holes, and
  clean smears.