25% DISCOUNT, SLIGHTLY DAMAGED, LIMITED SUPPLY - This is the revised edition of the popular manual, with updated information on everything from on-site preplanning and layout through the construction of footings, foundations, walls, fireplaces and chimneys.
There's an added appendix on safety regulations, with all the applicable OSHA sections pulled together into one handy condensed reference. There's new information on concrete, masonry and seismic reinforcement. Plus improved estimating techniques to help you win more construction bids.
The emphasis is on integrating new techniques and improved materials with the tried-and-true methods. Includes information on cement and mortar types, mixes, coloring agents and additives, and suggestions on when, where and how to use them; calculating footing and foundation loads, with tables and formulas to use as references; forming materials and forming systems; pouring and reinforcing concrete slabs and flatwork; block and brick wall construction, including seismic requirements; crack control, masonry veneer construction, brick floors and pavements, including design considerations and materials; and cleaning, painting and repairing all types of masonry.
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- Planning, Site Work and Surveying, 5
- Planning the job, 5
- Surveying for Footings and Foundations, 11
- Benchmarks and Elevations, 14
- Staking Out a Building, 16
- Measuring and laying Out Horizontal Angles, 17
- Concrete Characteristics and Properties, 21
- Portland Cement, 21
- Aggregate, 22
- Water, 23
- Material Proportions, 23
- Preparing Small Batches of Concrete, 24
- Common Flaws in Concrete, 26
- Admixtures, 26
- Coloring Concrete, 28
- The Curing Process, 31
- Surface Treatments for Concrete, 32
- Testing Concrete, 32
- Estimating Concrete for Small Jobs, 34
- Mortar, 37
- Mortar Components, 37
- Properties of Mortar, 40
- Mortar Types and Uses, 42
- Mixing Mortar, 43
- How to Place Mortar, 45
- Special Conditions, 46
- Preventing Efflorescence, 48
- Estimating Mortar, 48
- Sizing and Building Concrete Footings, 51
- Footings and Load, 51
- Sizing Wall and Pier Footings, 54
- Forms for Concrete Footings, 57
- Steel Reinforcement in Concrete Footings, 58
- Pouring Concrete Footings, 60
- After You Pour, 61
- Slab and Block Foundations, and Retaining Walls, 63
- Slab Foundations, 64
- Stepped Foundations, 66
- Masonry Materials, 66
- Preparing to Build, 67
- Laying the First Course, 72
- Pilasters, 74
- Masonry Retaining Walls, 75
- Estimating Block for Concrete Block Walls, 76
- Pier and Grade Beam Foundations, 79
- Pier Foundations, 79
- Grade Beams, 82
- Concrete Form Construction, 85
- Form Materials, 85
- Tables for Form Design, 88
- Building the Forms, 93
- Prefabricated Forms, 94
- Form Stripping and Maintenance, 102
- Poured Concrete, 105
- Common Concrete Delivery Problems, 105
- The Importance of Water, 106
- Placing the Concrete, 106
- Finishing the Slab, 108
- Curing Concrete, 110
- Controlling Cracking in Concrete, 110
- Pouring Concrete in Cold Weather, 113
- Pouring Concrete in Hot Weather, 113
- Pouring Sidewalks and Driveways, 113
- Precast Concrete Slab Sidewalks, 116
- Reinforced Masonry Construction, 119
- Masonry Walls and Partitions, 119
- Openings in Masonry Walls, 123
- Reinforcing and Crack Control in Masonry Walls, 129
- Control Joints, 129
- Reinforcement for Masonry Walls, 131
- Anchors for Masonry Walls, 133
- Expansion Joints, 137
- Sealants, 138
- Brick Wall Construction, 141
- Bonds and Patterns in Brickwork, 142
- Mortar Joints, 148
- Salvaged Brick, 150
- Estimating Brick Quantities, 151
- Brick Veneer Construction, 153
- Properties of Brick Veneer, 153
- Foundations for Brick Veneer, 154
- Selecting Materials, 154
- Supporting Veneer, 158
- Allowing for Movement, 159
- Lintels, Sills and Jambs, 162
- Attaching Brick Veneer to an Existing Structure, 163
- Brick Veneer Over Metal Studs, 164
- Cavity Walls, 165
- Caulking and Sealants, 167
- Limestone, 169
- How to Store Limestone, 169
- How to Handle Limestone, 170
- Supporting Limestone, 171
- Making Joints, 173
- Setting Limestone in Cold Weather, 174
- Dry Setting, 175
- Sealants and Joint Movement, 175
- Dampproofing, 177
- Cleaning Limestone, 178
- Removing Stains from Limestone, 179
- Repairing Damaged Stone, 180
- Cleaning and Painting Brick Masonry, 183
- Cleaning Brick Masonry, 184
- Efflorescence, 187
- Removing Some Common Brick Stains, 188
- Painting Brick Masonry, 189
- Masonry Paints, 191
- Painting Near Unpainted Masonry, 193
- Flashing and Moisture Control, 195
- Flashing Materials, 195
- How to Install Flashing, 196
- Where to Install Flashing, 197
- Weep Holes, 199
- Controlling Moisture in Brick Veneer and Cavity Walls, 200
- Sealants and Caulking, 201
- Chimneys and Fireplaces, 203
- Flues, 203
- Fireplaces, 211
- Floors and Pavements, 219
- Selecting the Right Brick for the Job, 219
- Planning the Job, 220
- Consider the Site, 221
- Selecting the Color, Texture and Bond Pattern, 221
- Joints, 222
- Base Materials, 224
- Setting Beds, 227
- Cushion Materials, 228
- Construction Safety, 231
- Occupational Safety and Health Act, 231
- OSHA Standards, 233
- Subpart H. Material Handling, Storage, Use and Disposal, 251
- Subpart l. Tools-Hand and Power, 251
- Subpart K. Electrical, 251
- Subpart L. Ladders and Scaffolding, 252
- Index, 293
Planning, Site Work and Surveying
This book is a guide to methods, materials and techniques used by professional masonry and concrete contractors. Masonry is an ancient profession that in some ways has changed very little for centuries. But it's also a modern profession, with techniques and materials improving as science makes new discoveries. The emphasis throughout this new edition is on modern practices. But that doesn't mean the tried and true methods that really are still the best are neglected.
I've written this manual to cover all phases of masonry and concrete construction. You'll find everything from on-site preplanning, through footings, foundations and walls. From fireplaces and chimneys to seismic reinforcement. From brick and limestone veneer construction to techniques for stain removal. There are in-depth discussions of the materials you'll use - the properties and characteristics of ingredients found in a batch of cement, for example.
Throughout this revised edition, I've either expanded or updated every section. Often I've done both. And I've emphasized safety. There's an entire chapter devoted to the Occupational Safety & Health Act. In this section you'll find all the applicable OSHA sections pulled together into a handy condensed form. And finally, there's information that will help you make bid-winning estimates for all kinds of masonry and concrete construction.
Of course, this book can't cover everything you might ever want to know about masonry and concrete. No single volume could. I wrote it for the busy, working masonry and concrete contractor who needs a handy reference to keep in the cab of his truck. When you're out on the job site and need to know a formula or how to deal with some problem, you've got the help you need close at hand. And back at the office, you're sure to use it as you're going over blueprints and writing estimates.
Planning the Job
In this chapter, we'll cover what you need to know and do before you start working at the job site. Since you'll be involved at the very beginning of a building project, with the foundation, you have to make sure it's in the right place. The framers will simply build on the footing you laid. If you've built it partly on the neighbor's lot, or a few inches over the setback line, and it's not discovered until after the roof is finished, you're not going to like their choice of who to blame.
Let's begin at the beginning - with the building code.
Check the Building Code
All residential and commercial construction must comply with local building codes and requirements. So your first step, before starting any project, is always to check the code. The local building inspector or city engineer should have copies of the current code available.
The first sections of the building code cover the general provisions and define the terms used in the code. The rest of the code covers space and structural requirements, fire safety and many other conditions and limitations. Building codes often spell out each and every detail. That makes it easy to work to the code once you know where to look.
Building codes vary in their details, but most use the same standard terms. Let's look at some of these definitions. Many of them are illustrated in Figure 1-1.
Building Line - A legal-determined boundary that no part of the building can cross. Exceptions are common, but the details vary widely. Never assume that what's allowed in your town is also OK in the next county. Always check the code before you start work.
Terms used in the building code
Distance Separation - This describes the amount of open space required between buildings. Open space helps keep fire from spreading from one structure to its neighbors.
Lot Line - A surveyed and recorded boundary that separates one piece of property from another. The same phrase also describes the legally determined boundary that separates a piece of private property from a public street or other public property.
Premise - A term used to describe collectively a piece of property as well as any buildings or structures on it.
Property Line -The legal boundaries marking a lot or parcel of property.
Setback - The open space required between a building line and the street centerline.
Street Line - A boundary separating a lot or parcel of land from the street. The street line and building line are the same if there's no setback required.
Basement - A space in a building that meets both of the following requirements: First, it's partly below grade. Second, more than one-half of its height, measured floor to ceiling, is above the average outside grade. Most codes allow habitable space in a basement if the basement floor isn't more than 4 feet below the average outside grade. Most codes also treat a basement as a story if the floor directly above it is at least 7 feet above the finished grade. See Figure 1-2.
Cellar - A space in a building that's similar to a basement, except for the following differences. First, the floor level is more than 4 feet below the level of the aver- age outside grade. Second, less than one-half a cellar's floor-to-ceiling height is above the average outside grade. Most codes don't allow habitable space in cellars, although a recreation room is usually allowed. Finally, cellars are rarely counted as a story. See Figure 1-3.
Check the Site Deed
There are several more tasks I recommend completing at this early stage. First, check the site deed. Watch out for covenants and/or easements. If you need to file a plot plan with a local official or agency, do so now, before you start work. Hire a licensed surveyor to check the site at this time. You must build within the established property lines and on the correct lot. Having a current survey of the lot provides a margin of protection for you as a contractor and for the property owner. Lawsuits are expensive and become even more so when you include your lost productivity.
Figure 1-2 Basement location with respect to grade level | Figure 1-3 Cellar location with respect to grade level
Consider the Building Permit
All contractors, including those in masonry and concrete, need to be aware of the potential problems with building permits. In most areas, no work may begin without a permit in hand. Failure to comply with permit-issuing procedures or the terms of the permit itself can lead to heavy fines. Worse yet, these fines are often retroactive to the date that construction began.
Once you have a building permit, you'll notice it lists specific required inspections. These happen throughout construction as specific tasks are completed. It's your responsibility as a contractor or subcontractor to notify the inspector's office whenever your work nears the point of needing an inspection. Always give the inspector's office as much advance notice as possible.
That way, work won't be held up while you wait for an inspection.
Issuing a certificate of occupancy is the final step in the inspection/permit process. This certificate shows that the construction covered by your budding permit is complete. It also certifies performance and passing of the final inspection.
Meeting the Standards
If you and your company undertake large projects, you'll probably be required to apply standard references. A standard reference, or a standard, is a specification, code, guide or procedure recognized and accepted throughout the industry. Some organizations that issue standards that apply to concrete and masonry construction are the American Society for Testing and Materials (ASTM), American National Standards Institute (ANSI), American Concrete Institute, National Concrete Masonry Institute and the Brick Institute of America.
Doing a Site Survey
We've already touched on the reasons for having a survey made by a licensed surveyor before any work is started. At this point I want to mention several good reasons for making your own survey as well.
Double-checking the setback against what the code requires is a smart move. Why? If there's an error, a building inspector is sure to spot it and slap a stop work order on the whole job site. Then you'll find yourself embroiled in legal action with the city, the general contractor, the land owner or all three. Double-checking the separation distance against what the code calls for is another good idea. Here again, an error in measurements is likely to lead to a dispute that ends up in court.
Doing your own surveying gives you familiarity with the site that you just can't get any other way. Plus, this early survey gives you a head start on the survey work for the foundation.
Both of the measurements just mentioned are easy to check. Do it! At this point any error you find can be fixed on paper. All it takes is a minute or two and your eraser and pencil. Fixing an error like this after you've started work costs far more. In fact, it could cost you your business.
While you're checking the site plan, give some thought to where you'll store materials on this job site. Remember, they're heavy. You can't pile them just anywhere. Take the time to check the site plans for underground tanks. At the job site, check any paved areas. Can they withstand the materials' weight? Also be sure you don't overload your vehicles - that's likely to cause an accident. Figure 1-4 shows the weights of the most common materials you'll use as a concrete or masonry contractor. Some of these figures will vary with the material's moisture content or texture of the material.
Soil Surveys and Analysis
Before you plan, let alone build, footings, foundations or walls, you need to know if the soil can support the structure. This is called the loadbearing capacity of a soil, and it varies with the kind of soil. How do you find out what kind of soil you're working with on a job site?
The U.S. Soil Conservation Service's soil survey for the area is your best bet. Their surveys cover all the information you need, and more. The Soil Conservation Service collects soil, climate and geographic data worldwide. Their maps plot this data over the top of an aerial photograph. They also publish written reports to match the mapped areas, which have even more detailed data. But the maps alone usually have all the information you'll need. They show.
soil's grain size
depth to bedrock
boundaries between soil types
seasonal high water table levels
The maps and reports aren't very expensive and you can order copies by calling (202) 205-0026 or writing to:
Superintendent of documents
United States Government Printing Office
Washington, DC 20402
|Common Brick, 1-1/2" x 4" x 8-1/4"||5.4 lb each, 2.7 tons per 1,000|
|Fire brick, 9" x 4-1/2" x 2-1/2"||7 lb each, 3.5 tons per 1,000|
|Face brick, 2-1/4" x 4-1/4" x 8-1/2"||6.48 lb each, 3.24 tons per 1,000|
|Paving brick, 2-1/4" x 4" x 8-1/4"||6.75 lb each, 3.37 tons per 1,000|
|Portland cement||94 lb/bag, 100 lb/CF, 2,700 lb/CY|
|Concrete||100-160 lb/CF, 3800-4100 lb/CY|
|Crushed stone||100 lb/CF, 2,700 lb/CY|
|Gravel||95-120 lb/CF, 2,565-3,240 lb/CY|
|Hydrated lime||50 lb/bag|
|Masonry cement||70 lb/bag|
|Sand (dry)||97-112 lb/CF, 2,600-3,000 lb/CY|
|Sand (moist)||112-127 lb/CF, 2,600-3000 lb/CY|
|Sand (wet)||127-140 lb/CF, 3,400-3,800 lb/CY|
|Sand (shovel full, dry)||15 lb|
Weights of common construction materials
If there's an agricultural extension bureau in the area, you can visit their office. The staff there can often answer your questions about local soils. They may also have maps that cover the information you need.
The best foundation-bed soil is one that:
supports the building's weight
doesn't swell when wet
doesn't shrink as it dries
isn't affected by frost heave
You're probably not going to find that ideal foundation bed soil. What you hope to find is the next best thing: a dry, well-compacted, sandy clay soil. Figure 1-5 lists some common soils and their loadbearing capacities.
Let's look at different kinds of soils now. We'll see what sorts of problems there are and how you can deal with them.
Rock isn't always bedrock, although it's easy to mistake a thin layer of rock for bedrock. Under the layer of rock is a bed of soft clay or sand and that's what the building really rests on. But can a bed of soft clay or sand support the building? Take another look at Figure 1-5. The loadbearing capacity of soft bedrock is 16,000 lb/SF. But soft clay, at best, has a loadbearing capacity of only 2,000 lb/SE
Here's another pitfall that catches beginners: mistaking a large, buried boulder for solid bedrock. This isn't a safe bed for footings because the boulder may break loose when the weight of a building is added.
Sand swells or flows when wet. Then, as it dries, it shrinks and settles. All of these (settling, flowing, swelling and shrinking) are bad news. Footings can be ruined by any movement. The only time sand is safe to build on is when the moisture level is stable. If that's not the case, you can bet on the sand moving sooner or later.
This soaks up moisture like a sponge. And, like a sponge, clay soils expand as they take in more and more moisture. Footings and foundations can be lifted right up by this swelling action. And clay is slippery and unstable when it's wet. Add some weight to a footing on a bed like this and the soil squeezes right out from under it. That's not good. The foundation will either fail or become so unstable that the building won't be safe. But you can raise a clay soil's loadbearing capacity by improving the soils drainage. You just add a layer of gravel to the top of the soil and then compact both soil and gravel.
|Type of soil||Loadbearing capacity (lb/SF)|
|Hard bedrock, such as shale||30,000|
|Soft bedrock, such as shale||16,000|
|Well-compacted gravel or gravel/coarse sand mix||12,000|
|Dry, hard clay or well-compacted coarse sand||8,000|
|Moderately dry clay or coarse sand/clay mix||4,000 to 6,000|
|Ordinary clay/sand mix||3,000 to 4,000|
|Silt, sand loam or soft clay||1,000 to 2,000|
Loadbearing capacities of common soils
Peaty or Spongy Soils
Peaty or spongy soils need specially-designed foundations. When it comes to planning foundations or structures for a site with soil like this, you're out of your depth. It's a job for a structural engineer, not a mason.
Avoid fill if possible. if it's very well-settled there's a chance you won't have too many problems now or later. But differences in the depth and makeup of fill make it settle unevenly. Fill made from lots of different materials may have as many different loadbearing values as it has materials.
Acid or Alkali? What pH Testing Tells You
I mentioned that soil pH (a measurement of relative acidity or alkalinity) is one of the pieces of data given on sod maps. As a mason you need to know the pH of three things on the job site:
water used for mixing
If the water or soil's pH is less than 7, it's acidic. The lower the pH, the more acidic the soil or water. For example, a soil with a pH of 6.5 isn't very acidic. However, a soil with a pH of 4.5 is very acidic and may need special handling.
At the other end of the scale are pH values greater than 7. Soil or water in this range is alkaline. The higher the pH, the more alkaline the water or soil. What do you care if the soil or water is acidic or alkaline? Ground water or soil with a pH of 9 will quickly break down concrete or mortar made with Type I Normal portland cement. That's why you care. You'll have to use Type II, or better yet, Type V portland cement in the concrete and mortar. You'll see in the next chapter that these types of portland cement are sulfate resistant.
A pH of 7 is neutral. Something with a pH of 7 isn't acid or alkaline, but it's not a likely pH for soil or ground water.
Most state health departments require safe sanitation practices for drinking and waste water. If you're budding in an area without sewers, make sure you know all the regulations involved. If you can, take a look at your job site in spring or during wet weather when the water table is at or near its peak. This is the best and easiest time to spot any problems with drainage, such as areas where water collects or places where seepage might be a problem later on.
To test the drainage, you can make a percolation test. This test will tell you how well wastewater will disperse into the soil. Here's how:
At the job site, dig a hole. If you can't do this test in wet weather when the water table is high, saturate the hole with water before you do the test. Where I live the hole must be 2 feet deep and 18 inches in diameter. Check the regulations in your area.
Fill the hole with water. Then time how long it takes the water to drop I inch, 2 inches and 3 inches. Use a yardstick to measure the water.
Do steps 1 and 2 again and average the results. I look for about 5 to 7 minutes per inch.
If the water level drops quickly, it may mean that wastewater could flow into drinking water at some distant location. If it drops slowly you may have poor drainage. Be sure these problems are solved at the beginning of the job. They can be very expensive later on.
Frost heave describes the way soil is lifted up and disturbed when the water in it freezes. Water expands (by about 9 percent of its volume) when it freezes and pushes everything up. The soil in an area usually freezes to a certain depth and rarely below that. This depth is called the frost line. Below the frost line the soil isn't affected by the freeze-thaw cycle, so that's where you want to put the footings.
Surveying for Footings and Foundations
After all inspection work is complete, the next step is excavating. A good excavator will use a transit or some other sophisticated leveling device to position and locate the tops of footings, foundation walls and retaining walls. Don't let any excavator eyeball your job. No man alive can get it 100 percent correct, especially if the job site is uneven.
Even after a good excavator finishes his work, you probably should use your own instrument to make sure all the forms are level. Out-of-level forms or forms not set to the correct starting height will make it hard for any mason. For example, all mortar joints should be no more than 3/8 inch thick for structural strength. It's a bad practice for a mason to use thick joints to make up for depressions. And it uses up a lot of mortar. On the other hand, if a mason has to cut blocks to fit humps or correct the elevation on the first course, he'll use extra time and produce a lot of broken pieces.
The surveying work you'll want to do calls for two basic tools: a transit level and a graduated leveling rod. Let's discuss both tools a bit more before we start telling you how to use them.
There are many different types of this precision measuring instrument. At the top of the scale, in price as well as precision, are electronic levels with such features as automatic leveling, laser-guided targeting and digital readout/input. However, most masonry and concrete contractors don't need this much precision. A transit is probably adequate for your surveying needs. A transit level has three main parts: the telescope, the leveling vial, and the circle.
Telescope (or scope)
This is a precision sighting optical device. It makes the images you see through it bigger. You take a sighting on a point simply by centering it in the vertical and horizontal cross hairs of the scope.
This is a bubble-type level that works just like the bubble in an ordinary carpenter's level. However, it comes in different sensitivities. If you need precise readings, you'll need a sensitive leveling vial on the transit.
The horizontal circle is part of the plate that the scope rotates on. The circle, vertical or horizontal, is basically a scale that measures angles in degrees, marked by the divisions on the circle. There are 360 degrees in a circle. More precise transit levels have a second scale, called a vernier. A vernier lets you mea- sure angles more precisely because it divides degrees into minutes. There are 60 minutes in a degree. The best and most precise transits have a second vernier that divides minutes into seconds. There are 60 seconds in a minute.
The first step in any surveying operation is to center and level the transit. Follow the instructions in the manufacturer's user's manual. Generally these manuals are quite complete, clearly written and well-Illustrated. Your manual is the best resource for information that's specific to your instrument. Read it, use it and take care of it.
If you make readings using an out-of-level transit, the readings won't be true. Surveying with an out-of-level transit is a waste of time. Carelessness here can cost you everything, especially if it results in a stop work order for the whole project.
Graduated Leveling Rod (or Rod)
This is the second of your basic tools for surveying work. In a pinch, an ordinary 6-foot rule might work. But a rod is better because it's longer, by 4 to 9 feet, and it's easier to read accurately from a distance. The background color of a rod is white. Divisions for feet are in large red print while the other divisions are in black print. There are two types of rods which vary in the type of divisions used. Figure 1-6 shows an architect's rod. The divisions marked on this type of rod are feet (in red), and inches and eighths of an inch (in black). The engineer's rod is shown in Figure 1-7. The divisions marked on this rod are feet (in red), tenths of a foot and hundredths of a foot (in black).
This usually comes with the rod but once again you've two choices: the oval vernier or the snap-on target. Both kinds of targets have cross hairs and both work by sliding up and down the rod. Figure 1-6 shows a target on an architect's rod. Use the target's cross hairs to pinpoint elevation readings on the rod's scale.
I've known masons who use both sorts of rods as well as both types of targets in any combination. Choose the equipment you prefer or are most comfortable using.
It usually takes at least two people to take a reading with a transit and rod. You'll need someone to hold the pole and move it around as necessary. Have an assistant (or rod holder) do these tasks, following your directions. Make sure the assistant holds the rod as shown in Figure 1-8 with the fingertips, taking care not to cover the scale.
Sometimes you and the assistant will be so far apart you can't communicate with each other easily. If you're not equipped with electronic transceivers, you'll have to use hand signals. Figure 1-9 shows the most common hand signals for surveying work. There aren't many of them and most are pretty obvious, so they're easy to learn. Remember, both members of a surveying team must use the same signals for hand signals to work.
It's possible for one person to do surveying alone. You can take the sightings and make the rod readings with what's called a self-reading rod. The one-man system sometimes is faster and it will save you an assistant's wages. Look at the survey needs of each job before you choose between a team, or soloing on the surveying work. Estimate the time you'll spend trotting back and forth moving the rod. Balance what your time is worth against the wages for an assistant.
Standard surveyors' hand signals
The Question of Units
The measurements you'll find on site plans for heights and linear distances are usually in units of whole and decimal parts of a foot. The dimensions you'll find on building plans and blueprints are usually feet, inches and fractional parts of inches for units. Here are a few tips on how to convert between these two Systems:
8 one-hundredths of a foot (written as 0.08) is about 1 inch
1/8 inch is about 1 one-hundredth of a foot (written as 0.01)
Figure 1-10 lists inches and the most common fractions as decimal parts of a foot. Use it to find decimal equivalents in feet alone for measurements that are in inches and fractions. On the next page are a few examples.
Converting inches and fractions of inches to decimal equivalents in feet
Find the decimal equivalent, in feet alone, for 2 feet 7-1/8 inches.
Find 7 in the column under the heading Whole inches.
Read across the 7 row to the column labeled 1/8 under the heading Fractional parts of an inch.
The value listed there (0.59) is the decimal equivalent, in feet alone, for 7-1/8 inches.
Now add the 2 feet to get the decimal equivalent in feet alone, 2.59 feet.
Let's take one more example. What is 8 feet 4-1/2 inches in feet alone? Remember not to consider the 8 feet until the end.
Find 4 in the column labeled Whole inches.
Read across the 4 inch row to 1/2 in the column under the heading Fractional parts of an inch.
The value, in feet alone, for 4-1/2 inches is 0.38.
Add the 8 feet to get the decimal equivalent in feet alone, 8.38 feet.
Benchmarks and Elevations
Most buildings you work on as a masonry contractor have all the elevations specified. The elevations are based on a known elevation, called a benchmark. Usually one benchmark is enough, but on large jobs it's helpful to have several. The best benchmark is one that's easy to spot and difficult to move, like a bolt on a fire hydrant, the corner of a stone monument or a metal spike driven into a tree root. There's one final feature that's important in choosing a benchmark. Be certain it's located a good distance away from any of the construction action.
Keep accurate and up-to-date records of your survey work for each job. Good record keeping is a hallmark of a good businessman. It's also the best form of insurance you could possibly have. Finding the data later will be easier and you'll know it's current.
Finding Elevation Differences
You'll often have to find the difference in the elevations of two points. Let's work our way through a few examples to see how to do it.
Finding the difference in elevation of two points
For this first example let's assume you can see both points from one location. Set up, center and level your transit there. Then take readings of both points. The difference between the two readings is the difference in their elevations. We'll use Figure 1-11 to demonstrate this basic technique. Remember there are two questions here. First, which is higher, point A or point B? Second, how much higher is the higher point? It's obvious, from looking at Figure 1-11, that B is higher than A. But it often won't be so obvious on a job site. Here's how it works:
The reading for point A is 69"
Expressed in feet only, that's 5.75'
The reading for point B is 40" or 3.33'
To find the difference between these elevations, subtract 3.33 from 5.75 to get 2.42
So point B is higher than point A by 2.42 feet, or 29 inches.
Let's look at Figure 1-12 for a problem that's a little more complicated. Taking a reading on point C is no problem. Point D, however, is located on the underside of the floor joist, above your line of sight. Let's see how you find its elevation, and then find the difference between the two elevations.
The reading for point C is 4' 6-1/2"
Expressed in feet only, that's 4.54'
To take an elevation reading for point D, place the foot of the rod against point D on the bottom side of the floor joist. That's right, hold the rod upside down, and then take your reading.
The reading for point D is 7' 9-3/8" (above line of sight)
Expressed in feet only, that's 7.78'
To get the difference in elevation, add the two elevations (4.54' and 7.78') to get 12.32'
So point D is higher than point C by 12.32 feet.
Finding the difference when one point is above the line of site.
Finding the difference when two points can't be observed from one step.
Let's look at one more example. This time we'll assume that the points are so different in elevation that it's impossible to make sightings on both from one transit setup. We'll use Figure 1-13 for this example, and we'll find the elevation difference between point E and point H. This example also uses two new terms: plus sight and minus sight. Plus sights are readings taken from a point to the line of sight. Minus sights are readings taken from the line of sight to a point.
In this example, you'll use three transit setup locations to find the difference in elevation. At each of these locations, take two readings - one plus sight and one minus sight. Then add the plus sights from the three locations together. Then add the minus sights together. If the sum of the plus sights is larger, point H is higher than point E. If the sum of the minus sights is larger, point E is higher. To find the elevation difference, follow these easy steps:
Convert all measurements to feet only
Add all the plus sights together:
2.59'+ 1.81'+ 7.85' = 12.25'
Add all the minus sights together:
8.38' + 9.97' + 1.21' = 19.56'
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Pouring and reinforcing concrete slabs and flatwork, including precast concrete and cold-weather work
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Quick and easy estimating techniques for all types of walls.
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Brick floors and pavements, including design considerations and materials.
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About the Author
Ken Nolan completed his apprenticeship with Local 57 of the Bricklayers and Allied Craftsmen in 1967. He worked in heavy construction and highway projects until he began his own construction company in 1973. In addition to running his company, Mr. Nolan spends much of his time teaching construction at occupational centers and colleges. He holds a degree in vocational education, and for the past 1 0 years has written the curriculum for the trade and technical education programs for the New York State Education Department. He has also served as a consultant on construction education to New York State colleges. Mr. Nolan has published four successful construction books, and holds patents for a number of construction tools he developed on the construction site.