Earth Pressure and Surcharge Loadings

The choice of lateral earth pressures used for design should take into account the method and sequence of construction, rigidity of the wall-anchor system, physical characteris­tics and stability of the ground mass to be supported, allowable wall deflections, space between anchors, anchor prestress, and potential for anchor yield. For stable ground masses, the final lateral earth pressures on a completed wall with two or more levels of anchors constructed from the top down can be calculated using the apparent earth pres­sure distributions shown in Fig. 8.50. For unstable or marginally stable ground masses, design earth pressures will be greater than those shown in Fig. 8.50. Therefore, loads

APPARENT EARTH

SOIL TYPE PRESSURE DISTRIBUTION

H = final wall height Ka = active earth pressure coefficient

Y = effective soil unit weight

Y = total soil unit weight m = reduction factor

qu = unconfined compressive strength

NOTES

(1) Ka = tan2 (45 – 2 )

(2) Ka = 1 – m (2qu/yH) but not

less than 0.25

m = 1 for overconsolidated clays

m = 0.4 for normally consolidated clay

(3) Value of 0.4 should be used for long-term excavations; values between 0.4 and 0.2 may be used for short-term conditions.

should be estimated using methods of slope stability analysis that include the effects of anchors, or that consider “interslice” forces.

In developing design earth pressures, consideration should be given to wall displace­ments that may affect adjacent structures or underground utilities. Rough estimates of set­tlement adjacent to braced or anchored flexible walls can be made using Fig. 8.51. If wall deflections estimated using Fig. 8.51 are excessive, a more detailed analysis can be made using beam-on-elastic-foundation, finite element, or other methods of analysis that con­sider soil-structure interaction effects. Where a structure or utility particularly sensitive to settlement is located close to a wall, wall deflections should be calculated on the basis of the loading, soil properties, anchor spacing, and wall element stiffness.

The distribution of earth pressure loading for anchored walls with one level of anchors can be assumed to be triangular and to be based on a lateral earth pressure coefficient (i. e., Ka, K0, or Kp) consistent with the expected wall deflection. To consider the case where excavation has advanced down to the first anchor level but the anchors have not yet been installed, the wall can be treated as a nongravity cantilevered wall and the earth pressure distribution assumed triangular. Overstressing of anchors

CURVE I

CURVE E = Stiff to very hard clay

CURVE Ш = Soft to medium day, factor of

safety against basal heave (5-1 equal to 2.0 ”У ” 4

CURVE Ш. = Soft to medium clay, factor of

safety agoinst basal heave (= 5-’ su ^ equol to 1.2 yH + q у

FIGURE 8.51 Settlement profiles behind braced or anchored walls. (From Standard Specifications for Highway Bridges, 2002, American Association of State Highway Officials, Washington, D. C., with permission)

should be avoided, because excessive anchor loads, relative to the capacity of the retained ground mass, can cause undesirable deflections, or passive failure of the wall into the retained soil. As with other walls, design lateral pressures for walls constructed from the top down must include the lateral pressure due to traffic or other surcharge loading.

Where there is no anchor level or only one, the magnitude and distribution of lateral resisting forces for embedded vertical elements in soil or rock can be determined as described in Art. 8.6.1. When two or more levels of anchors have been installed, the lateral resistance provided by embedded vertical elements will depend on the element stiffness and deflection under load.

Earth pressures on anchored walls constructed from the bottom up (fill construction) are affected by the construction method and sequence. These must be well specified, and the basis for lateral earth pressures fully documented. For walls with a single anchor level, consider a triangular distribution, defined by Kay per unit length of wall height, plus surcharge loads. For walls with multiple anchor levels, consider a rectangular pressure dis­tribution, derived by increasing the total force from the triangular pressure distribution just described by one-third and applying the force as a uniform pressure distribution.

Drainage considerations for anchored walls are similar to those discussed in Art. 8.6.2.

SPRAY-PAINTING BASICS

The information in this section is generally true for all spray applications. You’ll find other sug­gestions later in this chapter.

Wear a respirator mask with two replaceable organic-vapor filters. If you’re spray-painting exteriors, a half-face mask should be adequate. For interiors, where paint concentrations build up quickly, wear a full-face respirator mask.

Never touch a spray tip while it’s spraying:

It will inject paint into your skin (and blood­stream), which requires immediate medical attention, including removing the affected skin.

Carefully mask off everything you don’t want painted—from ceilings to windows to shrubs. To protect large expanses, use 112-in. painter’s mask­ing tape to attach high-density plastic sheeting. To cover baseboards, windowsills, and the like, apply 12-in.-wide masking paper. Careful mask­ing takes time, but it’s crucial to ensure crisp spray-painted edges.

Before turning on the pump, make sure the spray-gun trigger is locked, the pump’s pressure control is turned to low, and the priming lever is turned off.

Test the sprayer on an inconspicuous area first, to make sure it’s operating correctly and to famil­iarize yourself with its fan pattern and volume. If the pressure is correct, paint will stick when the spray tip is 12 in. from the wall. But if the paint bounces back at that distance (coating the sprayer and your gloved hand), reduce the pressure.

If the sprayer clogs often, the paint may be contaminated and need straining. Buy strainer bags at a paint store or, in a pinch, strain paint through an old pair of panty hose or nylons.

Keep the sprayer moving in long, straight strokes. Hold the spray tip 12 in. away from the surface and overlap passes 30 percent to 50 per­cent. To prevent uneven paint buildup, move the spray tip parallel to the surface. If the surface you’re painting has distinct edges, start spraying just before the edge and don’t release the trigger until the paint fan is past the far edge. If you must start in the middle of a wall, begin moving your arm before pulling the trigger.

Use a hose that’s long enough so you can move freely around the work site. For exterior jobs you’ll need a 100-ft. hose; for most interior jobs, a 50-ft. one. As you spray, hold a loop of the hose in your free hand to keep it out of your foot path— and away from freshly painted surfaces. Sprayer hoses come in 50-ft. lengths with couplings on both ends.

Start at the top and work down as you spray. Because a fine paint rain falls when you spray, better that it falls on unpainted surfaces—which will be painted over for a uniform finish.

Use a cardboard painting shield to keep paint overspray off adjacent surfaces you have already painted or won’t paint at all, as shown in the top photo on p. 462.

Keep spray tips clean because they are easily clogged. So when you’re done painting for the day, soak them in the appropriate vehicle (solvent for oil-based paint, hot water for latex). If the tip is really gunky, soak it in lacquer thinner.

Replace the spray tip if, after cleaning it, its spray pattern is still blotchy or the spray unit seems to be guzzling paint. Solids in the paint actually abrade the inside of the tip, enlarging it over time.

Keep filters clean and replace them often.

Using a paint-appropriate thinner, clean filters every time you change paint colors, at the end of each day, and if you’re pumping a lot of paint— say, 40 gal. by lunchtime. A 100-mesh filter is minimum; coarser filters will admit debris that can clog the tip.

Lead-Paint Safety

The presence of lead paint in older houses is seri­ous, but it’s probably not a dire problem if your home is well maintained and old paint is well adhered. Lead is most dangerous when it becomes airborne, especially during sanding or heat stripping, for then it can be inhaled and easily absorbed into the bloodstream. So be

Подпись:

methodical: Postpone any demolition or paint removal, test to see if lead paint is present, and develop a plan for dealing with it. Then wear proper safety equipment, confine lead-paint debris, and clean up thoroughly.

Lead: Some background. Lead-based paint adheres to almost any surface and weathers well, so it’s not surprising that it can be found in 90 percent of houses built before 1940. However, as lead paints health hazards became known in the 1950s, paint manufacturers began to phase it out. It was banned altogether in 1978 by the U. S. government.

Because lead is a neurological toxin, it is par­ticularly damaging to children 6 and younger, who seem drawn to it because it’s slightly sweet. Breathing or eating it can cause mental retarda­tion in children. In people of all ages, lead can also cause headaches, anemia, lethargy, kidney damage, high blood pressure, and other ailments.

Because of its durability, lead paint was com­monly used on exteriors, glossy kitchen and bath­room walls, in closets (where a single coat would last forever), and as an enamel on interior doors, windows, stair treads, and woodwork. So each time a swollen window or sticking door was forced open, it ground lead paint into flakes and dust. Roof leaks, drainage problems, and inade­quate ventilation add to the problem because excessive moisture causes the paint to degrade and detach sooner.

DEALING WITH LEAD: FIRST STEPS

If you suspect that your house has lead paint, test it to be sure. There are several options:

► To test a cut-out chip, buy an inexpensive lead-testing kit from a hardware store.

► Or order a lead-testing kit from an accredited testing lab; some of these kits test paint chips, whereas others test for dust wiped from floors; the EPA’s National Lead Information Center (NLIC) lists testing labs at www. epa. gov/lead/nlic. htm.

► Or hire a certified lead-paint inspector to survey all the painted surfaces in your house. This will cost several hundred dollars, but you’ll get a written report.

If the home has lead paint, here’s an alterna­tive set of options:

► If the paint is intact and you don’t have small children, either leave the lead paint alone or paint over it to seal it in place.

► If you have construction experience, your renovation isn’t extensive, and you’re fastidious about cleanup, remove the affected materials yourself—or cover them with 14-in. drywall.

► Hire an experienced lead-abatement contractor. This makes sense if your renovation is extensive, there are small children at home, you can afford to hire someone, and local codes require it.

Finally, think through the project carefully even if you plan on hiring a contractor. Lead abatement will be very disruptive. During abate­ment, where will you live? (It’s unwise to stay in a house with airborne lead dust.) Where will you store your possessions? How will debris be contained and disposed? Start by consulting local building codes and visiting the EPA’s excellent NLIC site mentioned earlier in this section.

LEAD ABATEMENT: AN OVERVIEW

Although comprehensive guidance for removing lead is beyond the scope of this book, these sug­gestions will start you in the right direction.

Dress for the job. Wear a half-face respirator mask with replaceable HEPA filter cartridges and snug-fitting goggles; a full-face mask with HEPA filters is also appropriate but may be hot to work

Подпись: SAFETY ALERT Whenever you take a break, stop for lunch, or quit for the day, wash your hands well. Otherwise, you can easily ingest lead dust. At the very least, change out of your work clothes and take a sponge bath at the site before changing into clean clothes. This is definitely one time when you don't want to take work home with you. ими in. Workers occasionally exposed to lead dust should wear at least an N100 disposable respira­tor. Disposable coveralls, gloves, and booties are also a must; tape shut neck, wrist and ankle openings. Finally, change out of lead-dust – contaminated work clothes at work because wearing them home can endanger your family.

Minimize on-site dust. Use a spray bottle to wet areas before hand-scraping or wet-sanding them. A shop vacuum with a HEPA filter can capture fine lead dust and prevent it from recirculating into the room; standard vacuum filters aren’t fine enough for the job. Stripping doors and window

ANCHORED WALL DESIGN

Anchored walls are made up of the same elements as cantilevered walls but are fur­nished with one or more tiers of anchors for additional lateral support. Anchors may be either prestressed or dead-man type. Tendons or bars extend from the wall face to a region beyond the active zone where they are grouted in place or mechanically anchored. Such walls are typically constructed from the top down in cut situations rather than fill conditions. Figure 8.49 illustrates an anchored wall and defines terminology.

WATER SUPPLY

Alternatives to traditional standards, materials, and procedures used in residential water supply systems are often more cost efficient.

Following are guidelines for water supply:

• Consider alternative materials for water mains and service pipes.

• Use multiple connections to one common service where feasible.

• Size water distribution pipes to meet the projected need.

• Substitute blow-off mechanisms for some, fire hydrants.

• Consider alternative meter arrangements.

Подпись: Water MainsПодпись: PVC pipeWATER SUPPLYPressure water pipe has been constructed of concrete, vitrified clay, lead, ductile iron, cast iron, asbestos cement, and wood. The newest material, plastic, most often in the form of polyvinyl chloride (PVC) or polybutylene (PB), has performed equally well or better than many of the more "traditional" materials.

PVC is relatively light weight, easier to install, more resistant to corrosion, and less expensive than many of the alternatives. An 8-inch PVC water main will save $2.00 to $2.50 per linear foot compared with an 8-inch ductile iron water main.

Most sizes of PVC pipe can be installed without the use of expensive machinery normally required to lower the pipe into a trench, since its relatively long lengths are easily balanced against its lighter per unit weight. PVC does not require complicated mechanical or glued joints. The bell and О-ring joints of standard PVC water pipe are wedged into place, saving material and labor costs.

An alternative to relatively expensive copper tubing for service lines is plastic tubing, usually manufactured from polyethylene (PE) or polybutylene (PB). Estimated savings of replacing 1-inch type К copper tubing with 1-inch plastic tubing is between $1.50 and $2.00 per linear foot.

Подпись: Water ServiceПодпись: ConnectionsAlthough local acceptance of plastic has been a slow process, both materials have been recognized under the major model plumbing codes. Available from most local suppliers, PB and PE have been rated at pressures well above those encountered in public water systems. Plastic tubing is flexible, lightweight, and easily joined with standard fittings. The relatively long lengths of most tubing insure that the number of joints will generally be limited to those at the main and the meter.

Saddle-type connections can be eliminated where a service line taps into the water main. A corporation stop assembly, used when tapping into ductile iron pipe, provides a complete, tight fitting connection without the saddle. The saddle adds $20 to $30 per tap, depending upon local factors. Crimping of tubing, especially near the tap, can be avoided by bedding the area within a foot or two of the connection with a local aggregate.

WATER SUPPLY

Vi" SERVICE LINE

WATER SUPPLY

Service line connection to water main

 

Communities should reevaluate standards that require a separate tap for each residence. Тар-in costs can be reduced significantly by branching off a tap to service more than one building or home. Multiple connections to one common service are frequently used with no adverse impact on performance.

A single water service can be installed along the common property line of adjoining lots. A standard wye or tee is used to branch off the common line near the meter, reducing the number of taps by 50 percent. Trenching costs and maintenance costs are also reduced since only one line is installed for two homes.

WATER SUPPLY
Common water service lines can serve a number of homes in cluster or. townhouse developments. A larger branch than the typical 3/4-inch service line may be required if more units are to be served. Cost benefits of multiple service lines are directly proportional to the number of units each line serves.

Multiple connections to a single water service line

Подпись: Sizing Accessory Items Many communities’ standards require a 6-inch, 8-inch, or even 10-inch minimum diameter for water mains. This often produces an overdesigned system.

Residential water supply and fire flow requirements should determine the size of water distribution piping. These requirements can often be met on short runs with 2-inch to 4-inch water lines. A larger main is generally nearby if it is necessary to install a hydrant for fire protection.

Cost savings are estimated at $4.50 per foot when a З-inch line is used compared to a 6-inch line.

Cost effective materials and construction techniques can be applied to meters, valves, hydrants and fittings. ;

Fire hydrants are routinely installed at the terminal end of water lines and at low lying points where it may be necessary to blow off the line. A blow-off mechanism can be substituted for hydrants that are not required for fire protection, saving approximately $1,000 per hydrant. A standard 2- inch blow off is usually adequate and can be installed by extending the main I with a short section of 2-inch tubing.

WATER SUPPLY

WATER SUPPLY

Подпись: STANDARD Подпись: Exterior water meter
An outdoor type water meter enclosed in a plastic meter box eliminates both the remote reader and the curbstop shut-off commonly installed with an indoor water meter, saving approximately $60.

АІ a safeguard against freezing in colder climates, the top of the meter is covered and placed below iocal frost depth.

WATER SUPPLY
Multiple meters can be housed in a single box, especially efficient when multiple connections are made to a single tap.

Подпись: Charlotte, North CarolinaПодпись: Mesa County, ColoradoWATER SUPPLYПодпись: EXAMPLES FROM THE DEMONSTRATION PROJECTS
In Lynton Place, built by the John Crosland Company, two major revisions to the city’s water main construction standards were proposed and subsequently approved by the city.

The first revision permitted a substitution of PVC water pipe for the cluctile iron pipe (DIP) water mains usually required. The second change permitted a common service line to serve two homes. This variance, which eliminated the need for two individual taps (and one tap fee), was achieved through the installation of a single 1-inch service line in place of two 3/4-inch lines. The innovations to the water system resulted in a reduction in total costs of $8,310, a savings of approximately $554 per unit.

In Mesa County, Colorado, water service to an individual building is typically installed using asbestos cement pipe. The county allowed Roger Ladd and Company to use polybutylene water service lines at the Coventry Club subdivision, resulting in a total savings of over $3,100 or approximately $63 per unit.

Подпись: Portland, OregonWATER SUPPLYПодпись: Lacey, WashingtonMike Robinson, President of Black Bull Enterprises, proposed substituting PVC water mains in place of the standard DIP in the North Meadow Village demonstration subdivision, and downsizing the water main from 8-inch lines to 6-inch fire hydrant and 4-inch domestic water lines, depending on the location. The city allowed both deviations from existing standards and permitted the elimination of individual meters for each unit with the understanding that the home owners’ association would maintain the system as privately owned. Water lines outside of the ROW were allowed based on the private ownership of the system.

The total water distribution system savings at North Meadow Village were estimated at $1,283 per unit. This reduction was after the inclusion of a $72,500 lawn sprinkler system. Had the $72,500 been excluded from the demonstration cost calculations, savings reflected in the per unit cost would have increased significantly.

The city allowed John Phillips, the builder, to install water mains outside the rights-of-way as long as easements were provided and the mains were in reasonably accessible locations.

Подпись: Blaine, Minnesota Подпись: Burlington, VermontPhillips also hooked one water line into two, three, or four water meters, meaning one tap and one corporation stop would serve as many as four dwellings. By placing four meters on a single tap, cost per unit was reduced from $530 to $211. This technique was practical only because the units were grouped and clustered. Total water service costs were reduced over $40,000.

Good Value Homes (GVH),

"•builder/developer of the Cloverleaf Farm 9th Addition, installed a 11/2- inch diameter water supply line to each eight-plex unit instead of the normal 2-inch line.

GVH also clustered the shut-off valves in one central location, and installed one water meter per building instead of the typical one meter per unit.

William R. Hauke, Hauke Building Supply, was permitted by the city to use one water line for four units in his infill demonstration, saving approximately $3,000.

Plastic pipe was also used in the following demonstrations: Oklahoma City, Oklahoma; Everett, Washington; and Charlotte, North Carolina


The great Yellow River dike failures in the Han Empire

The Yellow River dikes are continually maintained and raised. In the 2nd century BC, they had already attained a height of some ten meters. The regions they protect along the lower course of the river had become among the most populated of all China, as we have seen earlier. A first dike rupture occurred in 168 BC at a place called Suangao to the northwest of Kaifeng, near the origin of the Ji River (Figure 8.9). This rupture destroys what was called at the time the “metal dike”, to the east of Suangao, but in the end the breach is repaired.[414]

Yet again in 132 BC the Yellow River broke through its dikes at Huzi and poured out onto vast agricultural regions to the south. When the flood levels dropped the river con­tinued to occupy its new course, in the beds of the Si and the Huai rivers. The course change that had occurred five centuries earlier, in 602 BC, may have had limited impact, but it is not hard to imagine that the new change had rather dramatic consequences. Dike repairs were attempted, but without success as they failed once again. Finally the strug­gle was abandoned, perhaps under the influence of a counselor to the emperor whose lands were to the north of the breach, and therefore sheltered from the floods and per­haps increased in value due to the losses elsewhere.[415] [416] But the floods of the Yellow

River in its new course could no longer be controlled at all. In 120 BC, some 700,000

52

Подпись: Figure 8.9 Probable locations of the great dike ruptures of the Yellow River under the early Han (adapted from Liang Ruiju, Zheng Zhaojin, Hi Jialin, 1987, and other sources)
The great Yellow River dike failures in the Han Empire

victims had to be relocated from this region toward Shaanxi.

A particularly dry year occurred in 109 AD, 23 years after the dike rupture. Emperor Wudi took advantage of the situation to bring a considerable armed force to the site, and succeeded in blocking the breach and restoring the river back into its original bed. The blockage was accomplished by throwing bundles of branches into the breach between clusters of bamboo stalks, and quickly covering them with rocks and earth. Sima Qian is, here, no longer a historian but an actual eye witness to the event. He is even an actor in the play, for he tells of having carried bundles of branches on his back, as did every­one in the emperor’s entourage. At the outset of his work, the Emperor Wudi threw a jade ring into the river and also sacrificed a horse. Sima Qian faithfully recorded a psalm that the emperor composed on this occasion:

“The river broke through at Huzi;

What could we do?

Beneath its rushing waves,

Villages all became rivers,

The villages have all became rivers And there is no safety for the land. (…)

The river raged from its boundaries,

It has left its constant course.

Dragons and water monsters leap forth,

Free to wander afar.

Let it return to the old channel And we will truly bless the gods. (…)

Ask the Lord of the River for me,

“Why are you so cruel?

Your surging inundations will not cease;

You grieve my people!

The city of Niesang is awash;

The Huai and Si brim over,

So long, and yet you will not return You overstep the watery bounds!” (…)

The Lord of the River hears our plea But there is not enough brushwood.

There is not enough brushwood – The fault of the people of Wey.

They have wasted the land with fire – What can be used to check the waters?

We sink the forest bamboo And ballast the weir with stones.

We will stem the break at Xuanfang

53

And bring ten thousand blessings!”-”

Eighty years later, in 39 BC, new dike ruptures occur further to the north, and the technique for closing them is further improved. Cages of bamboo filled with stones are [417]

brought to the site by boat and sunk from the edges of the breach, progressively reduc­ing its width. Finally, boats are sunk at the site of the breach, and then the entire plug is covered with earth.[418]

There is no doubt that the situation on the lower course of the Yellow River contin­ues to preoccupy the leaders. In 6 BC, an engineer called Jia Ran (or Chia Jang) sub­mits a report to the emperor. He points out the potential danger of a poorly monitored dike, and calls attention to population and use of zones that should be kept open as flood plains, zones that represent a dangerous confinement of the main channel.

“At the present time, the nearer embankments stand at a distance of several hundred paces only from the water, and even the furthest are only several li from it. South of Liyang the old “Great Metal Dike” stretched north-westwards from the west bank of the Yellow River to the southern foot of the western mountains. It also ran eastwards to meet the eastern mountains. People built their cottages on the eastern side of the dike. After they have been living here a little over ten years, another dike was thrown out from the eastern mountains southward to connect with the Great Dike. Again, in the prefecture of Neihuang, a swamp with a circumference of several tens of li was drained by building a dike round it, and the governor of the district then gave the land within the dike to the people after they had lived here for more than ten years. Now people build cottages in it. These things I have myself seen. In the prefectures of Tungchun (Eastern Commandery) and Paima, the old “Great Embankment” is paralleled by several other embank­ments (outside it), and people live in between them. From the north of Liyang to the border of (the former state of) Wei, the old “Great Embankment” lies several tens of li from the river; but inside it there are also several rows of dykes which were built in earlier generations.”

These dikes, built without any planning, provoke the Yellow River into useless and dangerous changes of direction:

“Thus when the Yellow River flows from Honei north to Leiyang there is a stone embankment forcing it eastwards. When it reaches Tungchun and Phingkang, there is another stone embankment to force it north-west. When it arrives at Leiyang and Kuanhsia it meets a third, changing its flow north-eastwards again. At Tungchun and Chinpei it is diverted north-west, and at Weichun and Chaoyang north-east again – all by stone embankments. Thus in a dis­tance of only a little over a hundred li, it is turned westward twice and eastward three times…”[419]

Jia Ran has Taoist instincts. He proposes that the Yellow River be left to occupy its natural flood plains, free of habitations and obstacles. He specifically proposes that the populations in these zones be moved out, and that a natural outlet and floodplain toward the river’s ancient bed be opened further to the north (Figure 8.9). In the event that the emperor does not have the will to relocate the population, Jia Ran proposes an alterna­tive. This would be that a dense irrigation canal network be built with solid stone pro­tection, making it possible to irrigate the region during normal periods and to handle the floodwaters in wet periods, thus reducing their threat to the principle course of the river.

A third proposed solution, consisting simply of raising the existing dikes, is clearly nothing more than a token one. But the Emperor Aidi is young, the empire no longer having the strength it had under Wudi, and so the energetic measures proposed by Jia Ran are not adopted. This makes catastrophe inevitable.

The catastrophe occurred in 11 AD. The river comes out of its bed never to return, punctuating a three-year period of usurpation of power by a dignitary called Wang Mang who attempts political reform. The new course of the river, destined to be stable for nearly eight centuries, is some fifty kilometers further to the east (Figure 8.2) than the course into which the Wudi had redirected it. The event itself was devastating as can be imagined. And then regional famine ensued, since the crops were destroyed. In subse­quent years floods return over and over again, since the river was no longer in its diked bed. The population flees and there are revolts, subversively led by the secret society of the Red Eyebrows. All of these troubles likely contribute to the eviction of Wang Mang in 25 AD and the return to power of the Han family (these will become the “latter Han”).

Framing Tips for Every Task

When the lead framer is assigning tasks, he has to decide what information he has to tell the framer before starting the task. If the crew member has never done the task, the lead framer needs to explain it. If the framer has done this task many times, little needs to be said. If the framer’s knowledge is not clear, it’s best to review the task with him.

There are certain “tips" that experienced framers have developed for each task. Use the ones provided in this section or keep your own list to help your crew members.

Building Wall Tips

Material Movement for Walls

1. Locate wall framing so that once the wall is built, it can be raised into position as close to where it finally goes as possible.

2. Spread the headers, trimmers, cripples, and sills as close to their final position as possible.

3. Eight is an average number of 2 x 4 studs to carry.

4. You can use your leg to stabilize the studs you are spreading. Stabilize them with one arm and one leg to free up your other arm so that you can spread them one at a time. This way you won’t have to set them down, then pick them back up to spread them. (See photo.)

5. Select a straight plate for the top and double plates, and position any crown in the double plate in the opposite direction of the top plate crown. This will help straighten out the wall.

Nailing Walls

1. Nail the headers to the studs first. Make sure that they are flush on top and on the ends of the headers.

2. Nail the trimmers to the studs. Make sure that they are up tight against the bottom of the header and flush with the sides of the stud.

3. Nail the studs and cripples to the plates. Nail sills to the cripples and the trimmers. Make sure that all the connections are tight

and flush.

Squaring Walls

1. Align the bottom plate so that when it is raised, it will be as close to the final position as possible.

2. Attach the bottom plate to the floor along the inside chalk line for the wall. Toenail through the bottom plate into the floor so that the sheathing won’t cover the nails. If the wall is in position, it can be nailed on the inside, and the nails can be pulled out after the wall

is raised.

3. Use your tape measure to check the diagonal lengths of the wall.

4. Move the top part of the wall until the diagonal lengths are equal. Example: If the diagonal measurements are different by one inch, then move the long measure toward the short measure by one half inch diagonal measure. Make sure the measurements are exact.

5. Once the diagonals are the same, check by measuring the other diagonal.

6. Temporarily nail the top of the wall so that it will not move while you are sheathing it. Make sure you nail so that your nails won’t be covered by the sheathing.

Theatrical Fog Machine

Certain parts of the home, such as garages, at­tics, and crawl spaces, should be completely sealed from the rest of the house in order to prevent the passage of contaminated air into living spaces. One easy way to test for leaking airflow is to use a theatrical fog machine. This is the same equipment used onstage and in movies to create fog for special effects and can be rented from most theatrical supply com­panies. Place the unit in the area to be tested, turn it on to fill the space with fog, and then observe the adjoining areas for signs of fog that indicate where leaks must be sealed.

When testing the garage, seal the door and the open vents with tape and plastic to pre­vent the fog from escaping. The same can be done for attic and crawl-space vents and other
intentional openings to the outdoors. Com­mon air-infiltration points revealed by the fog test include electrical outlets, the junc­ture where the gypsum board meets the floor, and around poorly sealed plumbing, electri­cal, and ductwork penetrations. Theatrical fog testing is especially helpful when performed in conjunction with a blower door. This will al­low simulation of a variety of adverse weather conditions that may create unusual indoor air quality problems during inclement weather. Be sure to notify the fire department before you begin this type of test; otherwise a well­meaning neighbor who sees the smoke might dial 911 and set the fire trucks in motion.

Testing for Leakage in Air Distribution Systems A consultant can test for leakage in air distri­bution systems in a manner similar to blower door testing for a whole house. Doing this testing while the ductwork is still accessible, before it is covered with finishing materials, will simplify repairs. Supply and return regis­ters are sealed off so that the system can be de­pressurized using a blower door or calibrated fan. The combined airflow through all leak­age openings can then be determined. Ide­ally, leakage should be less than 3 percent. If a small amount of excess leakage is revealed, a theatrical fog machine can be used to trace the sources. If leakage is extensive, it will be neces­sary to examine all junctures and reseal where required prior to retesting.

Overall Stability

The overall stability of slopes in the vicinity of walls is considered part of the design of retaining walls. The overall stability of the retaining wall, retained slope, and foun­dation soil or rock can be evaluated for all walls using limiting equilibrium methods of analysis. AASHTO gives the following requirements:

A minimum factor of safety of 1.3 shall be used for walls designed for static loads, except the factor of safety shall be 1.5 for walls that support abutments, buildings, critical utilities, or other installations with a low tolerance for failure. A minimum factor of safety of 1.1 shall be used when designing walls for seismic loads. In all cases, the subsurface condi­tions and soil/rock properties of the wall site shall be adequately characterized through in – situ exploration and testing and/or laboratory testing…

8.6.3 Corrosion Protection

Prestressed anchors and anchor heads must be protected against corrosion that would result from ground and groundwater conditions at the site. The level of corrosion protec­tion depends on both the ground environment and the potential consequences of an anchor failure. Also, anchors for permanent walls require a higher level of corrosion protection than those for temporary walls.

BRUSH BASICS

The pros work steadily and methodically and note what works and what doesn’t. The following tips will help you keep the job moving and get great results.

Подпись: As you load your brush, dip it only ’/> in. to 1 in. into the paint before tapping the tip sharply against both sides of the pail to remove the excess. Подпись: Smart painters recycle brushes. This one began life as a finish-coat brush. Then, as it got tired and splayed, it was used for primer coats. When its bristles became too crusty and its handle separated from the ferrule, it became a duster. Подпись: with an initial upstroke, excess falls back onto the roller cover.

Acclimate a new brush. Stand a new brush in 1 in. of oil-based paint for 5 minutes. After absorbing a bit of paint, the new bristles will release paint more readily when you start to work. Whereas thirsty new brushes may drag at first. It’s not necessary to acclimate brushes when using latex, which works into bristles within 20 seconds to 30 seconds.

Avoid overloading your brush. Most pros have only h in. to 1 in. of paint in the bottom of a paint pail when edging—and the same amount on the tip of the brush. With this small amount, you’ll cut a cleaner paint line and keep paint off the brush handle and your hands. And, should the bucket tip over, you’ll have less mess to clean up.

Retrieve loose bristles. If a bristle comes loose and sticks to the surface, pick it out by dabbing lightly with the tip of the brush. Quality brushes rarely lose bristles.

Paint with gravity. This is close to an absolute rule. Paint, as a liquid or mist, always falls or drips downward, so it’s better if it lands on unpainted surfaces—rather than painted ones. Best sequence: ceilings, walls, trim, baseboards.

Paint with the grain. When painting trim, brush paint in the direction of the wood grain. Painting cross-grain doesn’t help paint adhere better and will look terrible if brushstrokes dry quickly.

Steady hand, straight paint. Few pros use masking tape to achieve straight lines when brushing paint onto trim, window casing, and the like. Pros feel that tape takes too much time to apply and sometimes lets the paint seep under, leaving a ragged line. Besides, during removal, tape can pull off paint. Patience and a steady hand work better. With a little practice, it’s easier than you might think.

ROLLER BASICS

Acclimate roller covers to paint. Before using a new roller cover, work paint into it well. Load the cover with paint. Then roll it up and down the paint ramp to work the paint down to the base of its nap, and remove the excess.

Pros prefer ramps for paint rollers in 5-gal. buckets. Unlike roller pans, 5-gal. buckets don’t need frequent refilling, and there’s plenty of room to load the roller cover and roll off the excess.

The expanded metal ramp’s open grid also allows excess paint to fall directly into the reservoir of paint, rather than coating the side of the bucket.

Roll upward, after loading a roller with paint.

If you roll downward instead, you’ll be more likely spray excess paint onto walls and floors. Instead,

Roll paint in a zigzag. Roller covers contain the most paint during the first three to five passes, so first roll a Wor an Nto distribute "fat paint,” which you can then reroll to spread the paint evenly.

Lighten up with the roller once the paint is spread on the wall. This is especially important for outside corners (corners that project into a room). Too much pressure can make the roller skid or leave roller-edge marks.

Подпись: If there are two painters, divide the job: The first painter leads the way with a brush to "edge" the corners, trim, and other hard-to-roll areas. The second painter follows, rolling over the edging to hide brush marks, thereby giving the wall a uniform texture. The first painter should edge out 2 in. to 3 in. from the trim and corners, and the second painter rolls to within V2 in. 1111 Подпись: I Moving with Spray Gunimage904Подпись: To achieve uniform spray applications, move with the tool, as shown, rather than remaining in one spot and swinging the spray gun in an arc.

ASPHALT-SHINGLE VALLEY

RiDGE SHiNGLES MADE FRoM

1/з of field shingle FoLDED oVER RiDGE &

 

EXTEND FIELD SHiNGLES To RiDGE.

 

ASPHALT-SHINGLE VALLEYASPHALT-SHINGLE VALLEY

Подпись: CLOSED-CUT VALLEYASPHALT-SHINGLE RIDGE

For centuries, wood shingles have been used exten­sively for roofing, and they continue to be very pop­ular. However, with the advent of the asphalt shingle, they have recently lost their dominance as a roofing material. Furthermore, their use continues to decline because of cost increases and a drop in the quality of the raw materials.

Roof shingles are made predominantly from clear western red cedar, but are also available in redwood and cypress. They are sawn on both sides to a taper, and have a uniform butt thickness. Standard shingles are 16 in. long; 18-in. and 24-in. lengths are also avail­able. Widths are random, usually in the 3-in. to 10-in. range. There are several grades of wood shingles; only the highest grade should be used for roofing.

In most cases, wood shingles will last longer if applied over open sheathing (see 166) because they will be able to breathe and dry out from both sides and therefore be less susceptible to rot and other moisture – related damage. Use solid sheathing and underlayment, however, for low pitch (3-in-12 and 3l/2-in-12) and in areas of severe wind-driven snow.

Chemically treated fire-rated shingles are available. They must be installed over solid sheathing that is cov­ered with a plastic-coated steel foil.

2 NAiLS PER SHiNGLE AT EDGE & ABOUT 1 iN. ABOVE COURSE LiNE

 

SPACED Roof SHEATHiNG COORDiNATES wITH

shingle exposure.

SEE 166

 

offset space between shingles 11/2 in. (MIN.) for THREE SUCCESSIVE

courses.

 

1-iN.

overhang

AT RAKE

 

double first course overhangs eave about 1 in.

 

1A-IN. (MIN SPACE BETWEEN shingles

 

double first course with

SIDES LAPPED 11/2 in. (MIN.).

 

FASCIA

 

EAVE FLASHING SEE 169A & B

 

RAKE FLASHING SEE 169C

 

for valley & HIP details, SEE 185A.

 

coursing is 4 in. to 7 IN.,

DEPENDING oN RooF PITCH SHiNGLE SIZE & SHiNGLE GRADE.

 

for RIDGE DETAIL, SEE 185B.

 

^ WOOD-SHINGLE ROOFING

 

ASPHALT-SHINGLE VALLEY

TRIM FiELD SHiNGLES TO CENTERLINE OF RIDGE.

 

ALTERNATE LAP DIRECTION OF MANUFACTURED HIP SHINGLES.

 

TRIM DOUBLE FIRST COURSE OF HIP SHINGLES TO LINE OF EAVE.

 

EAVE FLASHING SEE 169A & B

 

FASCIA

 

ASPHALT-SHINGLE VALLEY