The Effect of Temperature

Posted by on 11/ 11/ 15

Pore suctions have the effect of “pulling” the saturated zone nearer the ground surface than it would otherwise have been from where evaporation becomes pos­sible. When evaporation is significant then upward water flow takes place to re­place the water being evaporated. Evapotranspiration by vegetation also introduces an upward water flow towards roots in a similar manner. In hot climates, evap­oration can lead to upward moving water tens of metres above the phreatic sur­face and it can also lead to salts being lifted to the surface where they precipitate out in the soil pores forming calcretes and silcretes (Sabkha soils are an example of this).

Another cause of suction is seasonal ground freezing in high latitudes or at high altitudes. For reasons explained in Chapter 4, considerable ice wedges may form at the boundary between freezing caused by cold road surface temperatures and underlying non-frozen soils (Fig. 1.8). By this means, soils may heave by hundreds of millimetres in a winter season.

In spring, this ice melts, but the warmth comes from the surface so that the ice nearest the surface melts first. As there is still ice below it (and probably in the mar­gin of the roads where the surrounding ground is covered by snow and ice cleared from the road pavement), the water from the melted ice has nowhere to drain and extremely weak conditions can result (Fig. 1.9).

Подпись: Fig. 1.8 Ice lenses in a silty subgrade, Kuorevesi, Finland, Spring 2003. Reproduced by permission of N. Vuorimies
The Effect of Temperature

Just as evaporation, evapotranspiration and freezing are non-constant processes drawing water up from the groundwater zone, so rainfall is an intermittent supplier of water at, or near (via drains or soakaways) the surface causing a downward flow. A small amount of rain very rapidly cancels a high suction (thus suddenly reducing the effective stress and the frictional strength of a soil – see Section 1.4.3). It is partly for this reason that wet weather is so often associated with occurrence of slope distress in earthworks and in deformation of pavements.

The Effect of Temperature

Fig. 1.9 Thin asphaltic surfacing of a road lifted by traffic-induced water pressure during spring-thaw in Northern-Karelia, Finland. Reproduced by permission of M. Leppanen

Approaches to the Management of Lead-Based Paint on Steel Bridges

Posted by on 11/ 11/ 15

A number of methods have been advanced to effectively contain blasting debris and to min­imize the amount of waste generated from the management of lead-based paint from steel bridges. These methods are discussed in Art. 1.5.5 of this chapter. They can be broadly characterized as follows.

Deferring Maintenance. This approach does not serve to protect the bridge, and is the least satisfactory approach to protecting the large public investment represented by a major steel bridge.

Overcoating. This method consists of applying new layers of nonleaded paint over lead – based paint with the intent of extending the coating system for another 5 years or so. This method may reduce short-term costs and provide an agency more time while new innova­tions in lead paint removal are being developed. However, worker safety and environmen­tal issues still remain with the structure until the lead-based paint is removed. For example, the volume of unleaded paint increases with each coat, and thus a greater quan­tity of lead-contaminated paint must be disposed of as hazardous waste in many cases. Additionally, performance of the overcoating products has been highly variable, depend­ing on operator skill and experience, application conditions, existing paint that is being overcoated, and product consistency.

Removal and Repainting. This strategy requires the use of abrasive blasting or other means to remove the existing lead-based paint, followed by application of a coating system. This would provide the most durable and effective protection for steel bridge structures. However, its cost-effectiveness is diminished due to the need to collect and dispose of the spent paint and blasting grit of as hazardous waste. Worker safety during removal is a sig­nificant consideration.

Removing and Replacing Steel Members. This strategy involves removing members of the bridge during major rehabilitation efforts; removal of the lead-based paint within an enclosed workplace such as a fabricating shop; repainting, and restoring the members to their original location. Containment of the lead paint and blasting grit is more easily achieved with this approach. This method is generally cost-effective only on major reha­bilitation projects.

FILLER

Posted by on 11/ 11/ 15

The term filler means an aggregate that mostly passes through a specified sieve (0.063 mm in Europe, 0.075 mm in the United States). It should be emphasized that the material just discussed, which is generally called filler, denotes all the grains—that is, both those coming from the added filler and those occurring on fine and coarse aggregate grains in the form of dust. Thus if we want to know the behavior of a filler fraction in a given mixture, then all the grains below a specified sieve size in a final mineral blend should be separated, regardless of their source. All that material should be tested. If we only test the added filler, the results do not show the influence of the entire filler fraction on the properties of the mix.

The significant influence of filler on asphalt mixtures may be defined in the fol­lowing way (Anderson et al., 1982; Kandhal et al., 1998; Druschner, 2006): [11]

One could say that filler is the most underestimated component of SMA. After all, it constitutes from 8% to 12% of a mixture, which actually is a significant amount.

Next we will turn our attention to two concepts used in explaining the behavior of filler—the specific area of a filler and the content of voids in a compacted filler. These concepts can help describe various phenomena occurring in mixes.

Regulatory Framework

Posted by on 11/ 11/ 15

Hazardous waste is regulated under the RCRA if more than 220 lb (100 kg) of hazardous waste is generated each month, as is the case in most bridge paint removal projects. RCRA defines the concentrations of a waste that should be considered hazardous and establishes procedures for handling and disposing of hazardous waste. Disposing of waste is the responsibility of the waste generator. The lead-based paint and blasting grit recovered in bridge paint removal projects may contain concentrations of lead sufficient to classify it as hazardous, waste in all instances, the owner of the structure is considered the generator (in some states the contractor removing the paint may be considered a cogenerator). Subtitle C under RCRA is relevant to lead removal activities. Table 1.11 provides a listing of the per­tinent RCRA regulations.

Methods of testing wastes to determine whether the waste is hazardous are described in 40 CFR 261. Appendix II of that regulation describes the toxicity characteristic leaching procedure (TCLP, Method 1311) that must be used to analyze for hazardous constituents such as lead. Leachable levels of various elements that will establish waste as hazardous are found in Table 1 of 40 CFR 261.24 and are presented in Table 1.11. Wastes with any of the characteristics listed in Table 1.12 would be considered hazardous. For example,

TABLE 1.11 Pertinent Regulations of the Resource Conservation and Recovery Act (RCRA)

RCRA regulation

Description of regulation

40 CFR 260 40 CFR 262 40 CFR 261 40 CFR 268 40 CFR 263

Hazardous waste management system Standards applicable to generators of hazardous waste Identification and listing of hazardous waste Land disposal restrictions (land ban)

Standards applicable to transporters of hazardous waste

TABLE 1.12 RCRA Toxicity Characteristics and Waste Limits

RCRA waste number

Characteristic

Waste limit, ppm*

D001

Ignitability

D002

Corrosivity

pH<2; pH>12.5

D003

Reactivity

D004

Arsenic toxicity

5.0

D005

Barium toxicity

100.0

D006

Cadmium toxicity

1.0

D007

Chromium toxicity

5.0

D008

Lead toxicity

5.0

D009

Mercury toxicity

0.2

D010

Selenium toxicity

1.0

D011

Silver toxicity

5.0

*Corrosivity is measured in pH units.

Source: Based on Table 1 of 40 CFR 261.24.

using the TCLP testing method, if 5.0 mg/L or more of lead can be extracted from debris, the debris would be considered to be toxic and hazardous.

EPA regulates the amount of hazardous substances and waste that can be released into the environment under both CERCLA and SARA. Under these requirements, an owner is required to contain lead-based paint removed from a structure. A response could be initi­ated at a paint removal project if improper containment of dust or debris results in a release of lead to the environment. A reportable quantity of released leaded waste is 10 lb (4.5 kg). The report must be made to the National Response Center [(800) 424-8802] and to state and local regulatory authorities within 24 hours. The calculations presented in Table 1.13 demonstrate how to estimate the unit area of paint on a bridge surface that would equate to a reportable CERCLA release of lead.

CERLA and SARA regulations are found in 40 CPR 300 through 373. Discharges into the air and water area are also regulated by the CAA and CWA, respectively. EPA has man­dated enforcement of regulations to the states, leading to nonuniformity in the procedures to be followed and the stringency of requirements. Permits for blasting are required in some states but not others.

Because of the joint and several liability provision of CERCLA, it is possible that any one generator (or responsible party) may be liable for the entire waste disposal site cleanup. This is true even if there is no negligence on the part of the highway agency or its contrac­tors. Regulatory agencies do not recognize contractual obligations among responsible parties and will seek financial compensation from whoever has funds and can be connected to the contamination.

OSHA also has established several regulations applicable to worker protection during lead paint removal. These regulations are summarized in Table 1.14.

TABLE 1.13 Example Calculation of Surface Area Required to Generate a Unit Weight of Lead

Assumptions:

Lead in paint = 1% (10,000 ppm)

Dry film thickness (DFT) = 10 mil (0.010 in)

Density of dried paint = 1.5 g/cm3 (can range from 1.1 to 2.5)

Calculations:

1. Calculate volume of paint in 1 ft2 (1 ft2 = 929 cm2):

Volume = 929 cm2 (DFT X 2.54 cm/in)

= 929 cm2 (0.010 in X 2.54 cm/in)

= 23.60 cm3

2. Calculate weight of paint in 1 ft2:

Paint weight = density X volume

= 1.5 g/cm3 X 23.60 cm3 = 35.4 g

3. Calculate weight of lead in 1 ft2 of paint (1 ppm = 1 p. g/g):

Lead weight = ppm lead X paint wt/ft2 = 10,000 p. g/g X 35.4 g/ft2 = 354,000 p. g/ft2

4. Подпись: 454 g X 1,000,000 p.g/g =Calculate square feet required to generate 1 lb of lead (1 lb 454,000,000 p. g/g):

Area = 1 lb f wt of lead/ft2

= 454,000,000 p. g f 354,000 p. g/ft2 = 1282 ft2

Source: Adapted from K. A. Trimbler, Industrial Lead Paint Removal Handbook, 2d ed., Steel Structures

Painting Council/KTA-Tator, Inc., Pittsburgh, 1993.

TABLE 1.14 Regulations for Worker Protection during Paint Removal

RCRA regulation

Description

29 CFR 1926

Safety of health regulations for construction

29 CFR 1926.33

Access to employee exposure and medical records

29 CFR 1926.51

Sanitation

29 CFR 1926.59

Hazard communication

29 CFR 1926.62

Lead

29 CFR 1926.63

Cadmium

29 CFR 1926.103

Respiratory protection

Reciprocating saws

Posted by on 11/ 11/ 15

Another frequently used tool is the reciprocating saw, also called a sabersaw or a Sawzall®—the name given to Milwaukee’s® popular saw (see the bottom photo on the facing page). This tool allows you to cut in tight places and make curved cuts. Different blades are available for cutting through wood, metal, plaster, and plastic. For general use, I buy 6-in. bimetal blades, which cut through both wood and metal.

Chopsaws

The power-miter saw (generally referred to as a chopsaw) has revolutionized finish carpentry just as the circular saw revolutionized rough­framing carpentry. With a chopsaw, you can make precise square and angled cuts in framing lumber, door and window casings, and base­board trim. These saws are rugged and easy to use. When equipped with a fine blade, they can make glass-smooth cuts.

Sliding compound miter saw

This tool, the sliding compound miter saw, is a trim worker’s dream. It is essentially a chop saw that can cut angles across wide boards. I use it not only to cut baseboards and door casings, but also to cut across wide boards used in closets, blocks, headers, and cripples used in a house frame (see Resources on p. 279).

Lightweight tablesaw

It wasn’t long ago that tablesaws were cumber­some, heavy, and anything but portable. But times have changed. Now an on-site tablesaw can be moved easily by just one or two work­ers. But don’t be fooled by the lightweight label. These saws are well built, accurate, and with reasonable care will last for years (see Resources on p. 279).

Drills

An electric drill is a versatile tool on any job site. It’s capable of boring holes in all sorts of material and can also be used for driving screws and mixing paint or drywall compound. Most

FINE AGGREGATE

Posted by on 11/ 11/ 15

Throughout this book the term fine aggregate has been conventionally used as a term for the passive aggregate. Its upper limit depends on us—or more specifically, on

Подпись: (a) (b) FIGURE 3.1 Filling voids among coarse grains of aggregate with passive grains: (a) schematic diagram and (b) an actual example—mastic marked with dark gray color. (Photo courtesy of Krzysztof Blazejowski.)
the type of coarse grain previously in process of SMA design accepted as a skeleton maker. The task of the fine aggregate is to fill voids among the coarse aggregate particles and facilitate their interlocking, though it is likely to be put the other way round; the fine aggregate cannot disturb interlocking of the coarse aggregates. Such a disturbance can best be illustrated by an example of rounded, uncrushed aggregate (e. g., natural sand or uncrushed gravel) with smooth surfaces that allow the coarse aggregates to glide easily. Introducing such “hard balls” into an SMA mixture causes problems with the stabilization (interlocking) of the aggregate skeleton. That is why in many countries the incorporation of uncrushed aggregates in SMA has been lim­ited to only low volume roads, or its use has been generally banned.

Angularity is a feature that describes the properties of fine aggregates and is typically defined in terms of a flow test, which is an indirect method of angularity measurement. In Europe, the flow coefficient (method EN 933-6) is labeled with the Ecs symbol according to European Standard EN 13043 and describes the time necessary for a standard amount of aggregate to flow out of a suitably shaped vessel through an opening. Obviously the more crushed aggregate with a better microtex­ture, the longer the flow-out time; that is, rough or angular aggregates tend to lock up and not flow as quickly as smoother particles. Aggregate with an Ecs greater than or equal to 30 or 35 seconds (i. e., Ecs30 or Ecs35 category) is regarded as appropriate for SMA. There are also requirements concerning the angularity of fine aggregate applied in the United States.[10] Tests are carried out in accordance with the American Association of State Highway and Transportation Officials (AASHTO) T 304 Method A (ASTM C1252), and the required fine aggregate angularity (FAA) values are greater than or equal to 45% (NAPA QIS 122). Angularity can also be

measured according to ASTM D3398 and a National Aggregate Association (NAA) test method as well.

Remembering the positive influence of angularity on properties such as defor­mation resistance, we still have to take into account some negative factors like compaction resistance that accompany an increase in aggregate angularity. Moreover, research conducted by Stakston and Bahia (2003) showed that the effect of FAA depends on the source aggregate and its gradation and that angu­larity could have an adverse effect on a mixture’s resistance to shearing. Further reading on the influence of FAA on asphalt mixtures can be found in the Stakson and Bahia study or in other papers (Johnson et al., 2004; White et al., 2006).

The content of free voids in a compacted fine aggregate is undoubtedly an essen­tial parameter in SMA volumetric design. This characteristic may be tested through various methods, (e. g., the AASHTO T19 standard). The packing of consecutive SMA ingredients cannot be determined without prior knowledge of this characteris­tic. That approach to SMA design is discussed in Chapter 7 in the section devoted to U. S. and Dutch design methods.

The Method and the Madness

Posted by on 11/ 11/ 15

My reasons for choosing to live in such small houses include some envi­ronmental concerns. The two largest of my three, hand-built homes were made with only about 4,800 pounds of building materials each, less than 100 pounds of which went to the local landfill. Each produced less than 900 pounds of greenhouse gases during a typical Iowa winter. And, at 89 square feet, plus porch and loft, each fit snugly into a single parking space.

1

In contrast, the average American house consumes about three quarters of an acre of forest and produces about seven tons of construction waste. It emits 18 tons of greenhouse gases annually, and, at more than 2,349 square feet, it would most definitely not fit into a single parking space.

Finances informed my decision, too. Quality over quantity became my man­tra. I have never been interested in building anything quite like a standard travel trailer or mobile home. Travel trailers are typically designed for more mobility and less year-round comfort than I like, while most manufactured housing looks too much like manufactured housing for my taste. Common practice in the industry (though not inherent or exclusive to it) is to build fast and cheap, then mask shoddiness with finishes. This strategy has allowed mobile homes to become what advocates call "the most house for your mon­ey.” It has, in fact, helped to make manufactured housing one of the most af­fordable and, thus, most popular forms of housing in the United States today.

This is pretty much the opposite of the strategy I have adopted. I put the money saved on glitz and square footage into insulation, the reinforcement of structural elements, and detailing. At $30,000, Tumbleweed cost about one – sixth as much as the average American home. Only about $15,000 of this total was actually spent as cash on materials. That is less than half of what the average American household spends on furniture alone. The remaining $15,000 is about what I would have paid for labor had I not done it myself.

The cost of materials could have been nearly halved if more standard ma­terials were used. A more frugal decision, for example, would have been to skip the $1,000, custom-built, lancet window and install a $100, factory-built, square one instead. But I was, and I remain, a sucker for beauty.

The total cost was low when you consider I was able to pay it off before I moved in—but not so low when you consider that I sunk over $300 into every square foot. The standard $110 per square foot might seem more reason­able, but I succumbed to the urge to invest some of the money saved on quantity into quality. As a result, my current residence is both one of the cheapest houses around and the most expensive per square foot.

Still, my main reason for living in such a little home is nothing so grandiose as saving the world, nor so pragmatic as saving money. Truth be told, I simply do not have the time or patience for a larger house. I have found that, like

anything else that is superfluous, extra space merely gets in the way of my contentment. I wanted a place that would maintain my serene lifestyle, not a place that I would spend the rest of my life maintaining. I find nothing de­manding about Tumbleweed. Ev­erything is within arm’s reach and nothing is in the way—not even space itself.

image15

PIPING MATH

Posted by on 11/ 11/ 15

This section will profile formulas that can help you when working with pipes. Rather than talk about them, let’s look at them.

What plumber hasn’t had to figure the grading for a drainage pipe? De­termining the amount of fall needed for a drainpipe over a specified distance is no big mystery. Yet, I’ve known good plumbers who had trouble with cal­culating the grade of their pipes. In fact, some of them were so unsure of themselves that they started at the end of their runs and worked backwards, to the beginning, to insure enough grade. Not only is this more difficult and

Подпись: ✓ fast code fact As a rule of thumb, most codes require a minimum of one-quarter of an inch per foot of fall for drainage piping. There are exceptions. For example, large-diameter pipes may be installed with a minimum grade of one-eighth of an inch per foot. Too much grade is as bad as too little grade. A pipe with excessive grade will empty liquids before solids have cleared the pipe. Maintain a constant grade within the confines of your local plumbing code. time consuming, there is still no guar­antee that there will be enough room for the grade. Knowing how to figure the grade, fall, pitch, or whatever you want to call it, for a pipe is essential in the plumbing trade. And, it’s not diffi­cult. Let me show you what I mean.

Подпись: The capacity of pipes is as the square of their diameters. Thus, doubling the diameter of a pipe increases its capacity four times. The area of a pipe wall may be determined by the following formula: Area of pipe wall = 0.7854 x [Co.d. x o.d.) - (i.d. x i.d. )|

In a simple way of putting it, as­sume that you are installing a pipe that is 20 feet long and that will have a grade of V4-inch per foot. What will the drop from the top of the pipe be from one end to the other? At a grade of V-t-inch per foot, the pipe will drop one inch for every four feet it travels. A 20-foot piece of pipe will require a 5- inch drop in the scenario described. By dividing 4 into 20, I got an answer of 5, which is the number of inches of drop. That’s my simple way of doing it,

Подпись: The approximate weight of a piece of pipe may be determined by the following for-mulas: Cast-iron pipe: weight = (A- - BA x length x 0.2042 Steel pipe: weight = (A2 - B2) x length x 0.2199 Copper pipe: weight = (A2 - В2) x length x 0.2537 A = outside diameter of the pipe in inches В = inside diameter of the pipe in inches

FIGURE 1.6 ■ Piping. (Courtesy of McGraw-Hill)

FIGURE 1.7 ■ Determining pipe weight. (Courtesy of McGraw-Hill)

Подпись: The formula for calculating expansion or contraction in plastic piping is: T v T - F L L = Y x x 10 100
Подпись: L = expansion in inches Y = constant factor expressing inches of expansion per 100°F temperature change per 100 ft of pipe T = maximum temperature (°F) F = minimum temperature (°F) L = length of pipe run in feet

FIGURE 1.8 ■ Expansion in plastic piping. (Courtesy of McGraw-Hill)

The formulas for pipe radiation of heat are as follows:

PIPING MATH

D = outside diameter (OD) of pipe L = length of pipe needed in feet R = square feet of radiation needed

FIGURE 1.9 ■ Formulas for pipe radiation of heat. (Courtesy of McGraw-Hill)

but now let me give you the more proper way of doing it with a more so­phisticated formula.

If you are going to use the math formula, you must know the terms asso­ciated with it. Run is the horizontal distance that the pipe you are working with will cover, and this measurement is shown as the letter R. Grade is the slope of the pipe and is figured in inches per foot. To define grade in a for­mula, the letter G is used. Drop is the amount down from level or in more plumber-friendly words, it’s the difference in height from one end of the pipe to the other. As you might guess, drop is known by the letter D. Now let’s put this into a formula. To determine grade with the formula above, you would be looking at something like this: D = G X R. If you know some of the vari­ables, you can find the rest. For example, if you know how far the pipe has to run and what the maximum amount of drop can be, you can determine the grade. When you know the grade and the length of the run, you can deter­mine the drop. I already showed you how to find the drop if you know grade and run numbers. So, let’s assume an example where you know that the drop is 15 inches and the run is 60 feet, what is the grade? To find the answer, you divide the drop by the run, in this case you are dividing 15 by 60. The answer is.25 or V4-inch per foot of grade.

PIPING MATH

TEMPERATURE TIPS

 

Let me give you a few illustrations here that will help you deal with tempera­tures, heat loss, and mixing temperatures.

 

Temperature may be expressed according to the Fahrenheit (F) scale or the Celsius (Cl scale. To convert rC to °F or F to C, use the following formulas:

F = 1.8 x C * 32 C = 0.55555555 x ‘F – 32 ■C = F – 32 1.8

F = ( . x 1.8 + 32

 

FIGURE 1.10 ■ Temperature conversion. (Courtesy of McGraw-Hill)

 

To figure the Anal temperature when two different temperatures of water are mixed together, use the following formula:

(A x C) s – (B x D)

A В

A = weight of lower temperature water В = weight of higher temperature water C = lower temperature D = higher temperature

 

FIGURE 1.11 ■ Computing water temperature. (Courtesy of McGraw-Hill)

 

Radiation

3 ft of 1-in. pipe equal 1 ft" R.

2’Li lineal ft of 1’/ i-in. pipe equal 1 ft" R.

Hot water radiation gives off 150 Btu/ft- R/hr. Steam radiation gives off 240 Btu/ft – R/hr.

On greenhouse heating, figure ~/л ft ‘ R/fC glass.

1 ft“ of direct radiation condenses 0.25 lb water/hr.

 

-100°-30°

QC

Base temperature

-73

-100

-148

-68

-90

-130

-62

-80

-112

-57

-70

-94

-51

-60

-76

-46

-50

-58

-40

-40

-40

-34.4

-30

-22

-28.9

-20

-4

-23.3

-10

14

-17.8

0

32

-17.2

1

33.8

-16.7

2

35.6

-16.1

3

37.4

-15.6

4

39.2

-15.0

5

41.0

-14.4

6

42.8

-13.9

7

44.6

-13.3

8

46.4

-12.8

9

48.2

-12.2

10

50.0

-11.7

11

51.8

-11.1

12

53.6

-10.6

13

55.4

-10.0

14

57.2

ЗГ-7Г

°С

Base temperature

°F

-0.6

31

87.8

0

32

89.6

0.6

33

91.4

1.1

34

93.2

1.7

35

95.0

2.2

36

96.8

2.8

37

98.6

3.3

38

100.4

3.9

39

102.2

4.4

40

104.0

5.0

41

105.8

5.6

42

107.6

PIPING MATH

FIGURE 1.14 ■ Boiling points of water based on pressure. (Courtesy of McGraw-Hill)

Making the Grade

Posted by on 11/ 11/ 15
Подпись: Upon hearing that I planned to build a timber frame home with an earth roof, the immediate response from the building department supervisor was, "Are you a structural engineer? I'm not." I knew then that I would have to hire an engineer. But another problematic issue soon arose, revolving around the fact that I was felling my own trees (hardwood, no less) and chainsaw-milling them into posts and beams. The issue concerned the use of ungraded hardwood lumber. Finding an engineer was a process by itself, as I encountered resistance to the idea of using native timbers. Many engineers simply don't want to be bothered with "gray" areas when it comes to what they think of as unconventional building. Tracking down someone to grade my homespun hardwood timbers was even more difficult than finding the right engineer. We live in the northern part of Michigan's lower Peninsula. Numerous local sawmills process the fine maple, oak and beech stands in our region, but none of the ones I contacted graded hardwood for its structural properties, but only with respect to veneer lumber, flooring, and the like. I contacted a "certified" hardwood lumber grader through one of the mills, who made a 90-mile round trip to my place only to reveal that he didn't know how to grade posts and beams for structural purposes. So I cast my net further afield. Подпись: The Department of Forestry at Michigan State University referred me to the National Hardwood Lumber Association (NHLA) in Memphis, Tennessee. Through them I connected with a sympathetic inspector who proposed an alternative to having him visit my location and charging me the minimum fee of $470 a day, plus expenses. He volunteered to call the local "certified" inspector — the one who had already visited — and explain to him how to grade hardwood for structure. The grading was done according to guidelines from the Northeastern Lumber Manufacturers Association (NeLMA) in Maine. The inspector charged me $120 and apologized that the bill came to that much. It seemed quite reasonable to me, considering the time he spent educating himself to "make the grade." Incidentally, the building inspector was not the only one who needed the certified grading; my engineer also needed it in order to feel comfortable about assigning values to my timbers. Thankfully, my building inspector is basically on my side and seems to appreciate the lengths I've gone to satisfy code. I've maintained a cordial relationship with all the inspectors I've dealt with, and though it's been mighty frustrating at times, the good will is generally repaid in kind. It pays dividends to treat the building department as a resource, and not an adversary.

Mark Powers, owner-builder, Alonson, Michigan

Author’s note: The two lumber organizations mentioned above, NHLA and NeLMA, are listed in Appendix C.

In short, the grading of lumber can be an expensive proposition, which defeats the advantage of using local rough-cut lumber in the first place. At this time, despite widespread adaptation of the International Building Code, it is possible for most people in rural areas to build with non-graded lumber. Check on this with the town or county building inspector before placing a big lumber order with your local sawmill, or cutting quantities of your own lumber with a chainsaw mill. If evasion is a strategy that you have in mind — I am not advocating this, you understand — then you might want to gain the information anonymously.

My guess is that wherever the local forest products industry is strong, there will be (or soon will be) provisions such as the one recently adopted by New York to allow the use of rough-cut lumber. Economic considerations aside, you cannot easily purchase heavy timbers from ordinary building supply yards. Local sawmills, farm sawmills, and personal timber cutting (small chainsaw or bandsaw mills) are the realistic and affordable choices, and these are discussed in Chapter 3.

. AVOIDING KICKBACK

Posted by on 11/ 11/ 15

When the blade of a circular saw gets pinched by the wood, the power of the motor can force the saw backward—a safety hazard called kickback. In extreme cases, the saw can jump away from the material with the blade still spinning, harming anything in its path. To prevent kickback when using a circular saw, follow these guidelines:

■ Use a sharp, carbide-tipped blade.

■ Cut in a straight line.

■ Let the saw do the cutting—don’t force it. Forcing the cut can cause the blade to bind and kick back.

■ Always provide proper support for the stock. Avoid setups that al­low the material being cut to pinch the blade (see the illustration below).

■

Подпись: When you are cutting wood, support it properly. Unsupported wood can pinch the blade and cause the saw to kick back.

Подпись: Adjust the cutting depth. Always set the cutting depth so that the saw just barely cuts through the material. [Photo © Tony Mason] Подпись:If a kickback does occur, release the saw trigger immediately and let the blade stop. As long as the blade guard is working properly, there is little danger of injury. Don’t resume cutting until the cause of the kickback is determined and corrected.

. AVOIDING KICKBACK

Not enough support

The stock sags in the middle, pinching the blade.

Not enough support

c

The stock sags at

A

A

both ends, pinching the blade.

hi——————

. AVOIDING KICKBACK

The stock is supported on both sides of the cut, so the blade is not pinched.

Подпись: Use a chopsaw for speed and accuracy. With a chopsaw, it's easy to make precise cuts at different preset angles. This type of saw must be set on a good worktable, with outboard supports for longer boards. [Photo by HFHI/Steffan Hacker] Подпись: A hook can be helpful. Some new saws come with a built-in hook that allows you to hang the saw over a joist or a rafter when you're working up high. A Skyhook accessory is also available to retrofit on saws that lack this convenient feature (see Resources on p. 279). Подпись: The sliding compound miter saw makes short work of anything from 4x header stock to a small piece of door trim. [Photo by Don Charles Blom]