Legal Responsibility

Estimates by the FHWA indicate that there are an average of 15 signs per mile on the nation’s 3.8 million miles of streets and roadways [6]. The resultant 57 million traffic signs represent a huge investment in materials, labor, equipment, and maintenance costs. While this is a significant investment, improvements using standard traffic control signing are reported in the “1988 Annual Report on Highway Safety Improvement Programs” as having the highest benefit-cost ratio of any highway safety improvement [7]. Properly designed, located, and maintained standard traffic signs and other carefully conceived devices can be an effective method of increasing traffic and operational efficiency and subsequently decreasing the tort liability exposure of roadway agencies.

The concerns about tort liability judgments are valid, as the number of cases is steadily increasing. In almost every state, the shield of sovereign immunity either has been abolished by judicial decisions or has been eroded by legislative modifications to governmental immunity. In one state, for example, the legislature was instructed to enact comprehensive tort claim procedures in the near future or the doctrine of immu­nity would be abrogated by the state supreme court. In another state, the concept of sovereign immunity was declared unconstitutional [8].

A tort is a civil wrong or injury. The purpose of a tort action is to seek compensation for damages to property and individuals. The following elements must exist for a valid tort action:

• The defendant must owe a legal duty to the plaintiff.

• There must be a breach of duty; that is, the defendant must have failed to perform a

duty or performed it in an improper manner.

• The breach of duty must be a proximate cause of the accident that resulted.

• The plaintiff must have suffered damages as a result.

In highway-related tort cases, the first element is relatively easy to establish. Roadway authorities have been vested with the responsibility of providing reasonably safe travel opportunity for roadways under their jurisdiction. The failure of the roadway agency to properly perform that duty, and that this breach of duty was the proximate cause of an accident, are more difficult to establish. In most instances, establishing that a breach of the legal duty occurred becomes a major issue in tort liability cases. Plaintiffs typically will attempt to establish that the agency having roadway jurisdiction was negligent in its duty and/or a physical condition was permitted to exist that was a hazard.

Negligence is the failure to exercise such care as a reasonably prudent and careful person would use under similar circumstances. Roadway agencies can be judged neg­ligent in two ways: (1) wrongful performance (misfeasance), or (2) the omission of performance when some act should have been performed and was not (nonfeasance). Roadway agencies can, therefore, be judged negligent either by addressing a safety problem incorrectly or by ignoring it. The critical issue in highway tort liability is the care with which highway agencies perform their responsibilities. If it is judged that a reasonable standard of care was not exercised, then the responsible persons and/or organizations may be held liable for injuries and damages that resulted.

In an attempt to familiarize roadway agencies and their employees with the potential liability, and to make them aware of their duties and responsibilities to the traveling public, the NCHRP published Synthesis of Highway Practice 106: Practical Guidelines for Minimizing Tort Liability [8]. In particular, this publication advises agencies to supply a consistent highway environment for motorists. The use of standard design fea­tures and uniform traffic control devices is also emphasized.

All states are to adopt the standards of MUTCD as the basis for designing and installing traffic control devices. Some states adopt MUTCD in its entirety, while other states incorporate additional devices and practices into their manuals which address their specific roadway design and driver expectancy needs. MUTCD provides minimal require­ments, and states that do prepare their own manuals are required to conform to the nation­al standard. Additional devices not included in either the federal MUTCD or those of the states are frequently developed to provide motorist warning of roadway hazards which, ideally, should be eliminated. The reasons for not eliminating the hazard can include geo­metric constraints, planned improvements, usefulness of the condition for other purposes, burden of removing the condition, and the lack of a method to correct the situation. When the need to warn motorists involves commonly encountered hazards, such as a stop sign ahead on a rural roadway, then an appropriate warning device can be found in MUTCD. When the hazard is posed by unusual or unique conditions, however, the highway engi­neer is placed in the difficult position of identifying, or often designing, a warning device that provides a clear message to the motorist of the potential hazard. It should be empha­sized that the installation of a warning device does not remove the agency from liability, especially if it can be shown that it was reasonably possible to eliminate the hazard.

. Corner trim, J-channel, and undersill trim

The corner trim pieces, which receive the ends of the vinyl siding panels, must be installed straight and plumb or they won’t look attrac­tive. Hold a short, cutoff piece of vinyl corner post against the sheathed corner of the house
and mark the edge of the flange on both sides of the corner at the top and bottom of the wall. Snap a chalkline between the marks. Set a corner post Z in. to И in. down from the sof­fit, and drive a l^-in.-long nail at the top of a slot on both sides of the corner. The corner post hangs from these nails, allowing the vinyl to move. Hold the posts directly on the chalk­lines and drive nails about every 12 in. in both flanges, down to the bottom of the wall. Keep each nail in the center of its slot. The corner posts should extend Zi in. to 1 in. below the starter strip.

Most doors and windows have factory – made siding channels. If yours do not, install J-channel along the top and sides of the window to hide the ends of the siding. You can use a miter or a square cut at the top corners. Either way, at the ends of the top piece, leave 1-in.-long drain tabs that can be folded down over the window sides. This helps channel water down around the window (see the photo at left).

TRIM AROUND A DOOR. J-channel trim is nailed around the window and door frames, with a tab in the top piece bent to fit around the corner.

Подпись: SNAPSHOTS. Corner trim, J-channel, and undersill trim

Some volunteers prefer contrast between the white cor­ner trim and the brown siding, while others aren’t sure whether it looks attractive. . .

We install siding panels from the bottom up. . .

Each new course of panels snaps onto the one below You can’t drive the nails hard against the vinyl bea it needs to move. . .

Подпись: THE WORK GOES QUICKLY. With scaffolding set up on two sides of the house and a Habitat-size crew, this siding job moves along at a good pace. Short offcuts from one side of the house can often be used elsewhere to minimize waste.. Corner trim, J-channel, and undersill trim

VENTING TOILETS

Because they have the biggest drain and vent pipes of any fixture, toilets can be the trickiest to route vents for. When space beneath a toilet is not a problem, use a setup such as the one shown below, in "Venting a Toilet,” in which a 2-in. vent pipe rises vertically from a 3 by 2 combo, while the 3-in. drain continues on to the house main. The 3-in.-diameter toilet drain, allows the vent to be as far as 6 ft. from the fixture, as indicated in the table on p. 281.

When space is tight, say, on a second-floor bathroom with a finish ceilings below, the drain and vent pipes must descend less abruptly (see "Constricted Spaces,” below. Here, the critical detail is the angle at which the vent leaves the 3 by 2 combo: That vent takeoff must be 45° above a horizontal cross section of the toilet drain. If it is less than that, the outlet might clog with waste and no longer function as a vent. As important, the "horizontal” section of the vent that runs
between the takeoff and the stack must maintain a minimum upward pitch of 1/4 in. per foot.

When you’ve got two toilets back to back, you can save some space by picking up both with a single figure-5 fitting (double combo), like the small one in the bottom photo on p. 277. From the top of the fitting, send up a 2-in. or 3-in. vent; from the two side sockets use two 3-in. soil pipes serving the toilets; and use a long-sweep ell (or a combo) on the bottom, to send wastes on to the main drain. This fitting is about the only way to situate back-to-back water closets and is quite handy when adding a half bath that shares a wall with an existing bathroom.

OTHER VENTING OPTIONS

Common vents are appropriate where fixtures are side by side or back to back. This type of vent usually requires a figure-5 fitting.

Loop vents are commonly installed beneath an island counter in the middle of a room. The sink

drain is concealed easily enough in the floor plat­form, but the branch vent, lacking a nearby wall through which it can exit, requires some ingenu­ity. This problem is solved by the loop shown in "Venting an Island Sink,” below.

In addition to the fittings shown in the draw­ing, note these factors as well: the loop must rise as high under the counter as possible and at least 6 in. above the juncture of the trap arm and the sanitary tee, to preclude any siphoning of waste­water from the sink. The vent portions may be 1 ’/2-in. pipe, but the drain sections must be 2 in. in diameter, and drain sections must slope down­ward at least ‘/ in. per foot.

Mechanical vents, also known as air-admittance valves, or pop vents, allow you to use a fixture before the vent runs are complete (say, before you run a vent stack up through the roof). Here’s how they work: As water drains from a sink, it creates a partial vacuum within the pipes, depressing a spring inside the vent and sucking
air in. When the water is almost gone and the vacuum is equalized, the spring extends and pushes its diaphragm up, sealing off outside air once again.

Mechanical vents are temporary vents only.

The UPC allows them only if local jurisdictions permit them—and few do. Because valve mecha­nisms can wear out and allow septic gases into living spaces, mechanical vents must never be used as permanent vents or in enclosed spaces where they cannot draw air easily.

VENT TERMINATION

image585

To reduce chances that vent gases will enter the home, stack tops must be at least 6 in. above the upslope side of the roof and at least 3 ft. above any part of a skylight or window that can be opened. A vent stack must at least 12 in. horizontal distance from a parapet wall, dormer sidewalls, and the like. Finally, stacks must be correctly flashed to prevent roof leaks.

Подпись: When ordering supplies, order 20 percent more pipe than you think you'll need and at least a half-dozen extra of the more common fittings such as tees, combos, ells, and couplings. You'll also need straps and clamps to support pipe runs and consumables, such as solder or plastic-pipe cement and plumber's sand cloth. Most supply stores accept returns, but check their policy before ordering. 1111 Подпись: So vent gases won't enter the home, plumbing vents must terminate at least 3 ft. above an openable window, or a minimum of 10 ft. horizontal distance from an openable window at the same level. Подпись: GOING WITH THE

Uniformity Considerations and Necessary Deviations

While the advantages of uniformity far outweigh the disadvantages, there are some undesirable effects when complete uniformity is maintained. One of the principal disad­vantages is that strict uniformity may result in the failure to adopt an improved device or procedure simply because it is not in common use. In addition, total uniformity would require the specification of a separate traffic control device for every conceivable road­way geometric and traffic operational condition. This would be a monumental task that undoubtedly would still not cover every situation, while simultaneously increasing the size of MUTCD with devices of limited application.

This difficulty is recognized in MUTCD, which indicates that warning signs other than those specified in the manual may be required under special conditions [2, Sec. 2C.02]. MUTCD requires exercising good engineering judgment in determining the need for other warning devices. It also mandates that the innovative devices be under­stood easily by the motorist. Ensuring that warning signs are easily understood neces­sitates that they be of standard shape and color and that the legends be unambiguous and brief. Establishing the need for distinct warning devices can be accomplished by identifying when standard devices do not properly address unusual conditions. While these conditions are unusual, they can typically be classified into the same use cate­gories that are appropriate for standard warning signs. The Traffic Control Devices Handbook [3] identifies the following uses of warning devices:

• To indicate the presence of geometric features with potential hazards

• To define major changes in roadway character

• To mark obstructions or other physical hazards in or near the roadway

• To locate areas where hazards may exist under certain conditions

• To inform motorists of regulatory controls ahead

• To advise motorists of appropriate actions

The need to provide advance warning for unusual roadway, roadside, operational, and environmental conditions has resulted in the development of a wide diversity of devices. The majority of these devices can be categorized as warning signs containing different symbols and legends. Other warning devices include flashing beacons, rumble strips, pavement surface treatments, and pavement markings. Device complexity ranges from simple passive warning signs to devices that are activated by vehicle speed, headway, or presence on one or more approaches to a potentially hazardous roadway element. Further information on supplemental warning and rumble strips can be obtained from the National Cooperative Highway Research Program (NCHRP) publi­cations Synthesis of Highway Practice 186: Supplemental Advance Warning Devices and Synthesis of Highway Practice 191: Use of Rumble Strips to Enhance Safety [4, 5].

STEP 2 INSTALL THE LEDGER

On a house built over a basement or crawl space, a deck or porch can be attached to the house frame. Deck building then becomes a lot like framing a floor-joist system inside a house (see

Chapter 3). Step one in this process is to attach a ledger to the house frame. Straight, level, and solidly secured to the house, the ledger acts like a rim joist for the porch. It extends the full length of the porch, supporting its inboard side.

There are several concerns when attaching a ledger, and all of them are important. First, the ledger must be at least 21/2 in. below the level of the interior floor. When l/Tin. deck boards are screwed on top of the ledger, the deck will be l in. lower than the interior floor, which is just about right. If wheelchair accessibility is a concern, plan to build a small ramp to bridge the distance between the deck and the doorsill.

Reserve your best boards to use as ledgers— clear lumber with straight, square edges and

Подпись:Подпись: SubfloorПодпись: Rim joist Подпись: SillПодпись: Metal flashing Подпись: Foundation wallSTEP 2 INSTALL THE LEDGERПодпись: Sheathing Housewrap Подпись: INSTALLING A LEDGER WITHOUT FLASHING

no major imperfections (cracks, large knots, or warping). When installing a ledger, make sure water cannot get behind the ledger and into the house frame, where it could cause rot. And make sure the ledger is secured to the house in a man­ner that will hold for the life of the building.

Flash the ledger

Many builders like to use flashing when installing a ledger. Find out which types of flashing build­ers use in your area. I tend to use heavy-gauge aluminum behind the ledger, though I sometimes opt for high-quality galvanized sheet metal or even copper—expensive though it is—instead of aluminum. Although it can take a while, ocean air and city smog will gradually take their toll on aluminum flashing, causing it to deteriorate.

The flashing is installed before the exterior siding. It can be nailed directly to the wall fram­ing and rim joist if no sheathing has been used on the exterior walls. Otherwise, install the flashing on top of the wall sheathing (see the top illustration at right). Order flashing that is wide enough to extend several inches above the ledger and down over the rim joist. At door openings, cut the flashing just enough to bend it over and lay it flat on the subfloor. Use as few nails as possible when installing flashing, and keep them high on the wall. The ledger and exterior siding will hold the flashing in place. If you install housewrap (such as Tyvek or Barricade) over the wall sheathing, make sure the flashing tucks underneath the housewrap, as shown in the illustration.

In the dry Southwest, the ledger can be fas­tened directly on top of the flashing. Otherwise, use galvanized washers or PT shims to create a narrow (3/8-in. to!/2-in.) drainage space behind the ledger. This prevents buildup of moisture or mold.

On exterior decks it is best to use treated wood or synthetic decking. It is only a matter of time before untreated wood left exposed to the elements starts to rot. In some climates, even treated wood needs to be painted every year with an oil-based solution to prevent cracking and splitting.

1/2-in.-dia. bolt, installed through rim joist every 16 in. to 24 in.

Nut

Deck ledger

PT spacer,

3/8 in. to 1/2 in. thick, (galvanized washers can also be used as spacers)

Spacers allow water to flow behind ledger.

STEP 2 INSTALL THE LEDGER

Air space behind the deck ledger allows water to drain freely. Caulk bolt holes before inserting bolts.

MINI MINI MINI MINI MINI MINI MINI MINI MINI MINI MINI MINI MINI II MINI MINI MINI MINI MINI MINI MINI MINI MINI

 

STEP 2 INSTALL THE LEDGER

Подпись: Ismet and Rahime Osami are an inspiration to their daughter—making a new life for themselves in Tucson after fleeing Kosovo and building a new home with the help of Habitat. [Photo courtesy HFHI]STEP 2 INSTALL THE LEDGER

MAKING IT HAPPEN

Ismet Osmani and his wife, Rahime, fled Kosovo in the midst of ethnic strife and war and landed in Tucson, AZ, in April 2002. Five years later, with a four-year-old daughter and infant son in tow, they are on the path to homeownership, partnering with Habitat for Humanity Tucson.

“I used to live in a house over there, but it was burned, destroyed in the war," Ismet says of his home in Serbia. “Now we’ve been living in an apartment for five years, and you always have to be careful about noise and leaving stuff on the porch— it’s hard."

Ismet has a degree in education and was a coun­selor before he immigrated with his family. Now he
works as a driver for a hotel and holds down a sec­ond job in a restaurant—overqualified, perhaps, but he is glad to be working. Despite his busy schedule, Ismet dedicates every spare hour he has toward building his home. In fact, he finished his required 400 hours of “sweat equity" with Habitat long before the construction of his house was complete. When work kept him away from the house site, Ismet would often drive by to see how things were coming along.

This past summer Ismet and Rahime became U. S. citizens, an accomplishment earned through study, English lessons, and perseverance. They are extremely proud of all that they have been able to do since leaving Kosovo, and are ready to put down roots in Tucson.

“We worked hard and feel like we’ve accom­plished a lot," he says. “We’ll probably live the rest of our lives here." —Rebekah Daniel

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Installing a ledger without flashing

Here’s how to install a ledger against fiber- cement siding, wooden clapboards, or T1-11 siding without using flashing. Simply install the siding in the normal fashion, and hold the ledger away from the siding with PT wood spacers or galvanized washers. I’ve installed ledgers this way on a number of houses, including Habitat projects. To account for the angle of wood or fiber-cement clapboards, cut an angled PT spacer or use galvanized wash­ers in the manner shown in the bottom right illustration on p. 181. For that technique, first install the spacers, then bolt the ledger loosely in place. Complete the deck framing, then tighten the ledger installation bolts.

Nails won’t do when installing a ledger, though you can drive a few just to hold the board in position. My preference is to attach the ledger with ‘A-in.-dia. bolts that extend through the rim joist and are held fast with nuts and washers. Make sure the ledger is level before you begin boring holes for the bolts. Space bolts 16 in. to 24 in. apart. As extra insurance against unwanted water, apply some silicone caulk in each hole before inserting the bolt through the rim joist. Insert the bolts through the rim joist from the back, making sure you place a washer beneath each bolt’s head and nut.

 

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BUILDING A DECK FRAME

 

5 ft. 11 in.

 

Beam framing connector

 

5 ft. 8 in.

 

2×6 deck ledger bolted to house

 

Postcap

connector

Post

 

Concrete

pier

 

STEP 2 INSTALL THE LEDGER

2x6s

 

Joist hanger

 

Built-up girder detail

 

Joist-to-beam connection

 

This illustration shows one way to build a solid, long-lasting porch or deck frame.

 

FINDING THE LENGTH OF SUPPORTS POSTS

 

STEP 2 INSTALL THE LEDGER

The scrap 2×6 is the width of the girder or joist that will support the deck once the frame is built. The post will extend from the concrete pier to the deck frame.

 

STEP 2 INSTALL THE LEDGERSTEP 2 INSTALL THE LEDGERSTEP 2 INSTALL THE LEDGERSTEP 2 INSTALL THE LEDGER

Подпись: Install joist hangers with special nails. Joist hangers and other steel framing hardware should be installed with the special hanger nails sold with them. Common framing nails have thinner shanks, so they're not as strong. When you buy hanger nails, make sure they have a rust-resistant coating.STEP 2 INSTALL THE LEDGER

width and set the piers so they are in line with the ledger board and square with the building.

Next, measure the length for the posts that will extend from the piers to support the floor framing. You can do this with a 6-ft. level or with a shorter level attached to a straightedge (see the bottom illustration on p. 183). Lay the rim joist (or a scrap board of the same size) on top of each pier and set the level or straightedge on the ledger, extending it directly out over the pier. The distance between the rim joist on the pier and the level or straightedge is the post’s length. Cut those posts from PT 4 x4s; make them Vi in. short (be consistent) so that the deck will slope away from the house just a bit.

Cut the two end beams (girders) first, using PT 4x 6 lumber or doubled ix 6s, as shown in the top illustration on p. 183. For a deck that is 6 ft. wide, cut the two end beams at 5 ft.

8 in. The ledger and rim joist will add 3 in. to the overall width. Those beams connect to the ledger by a metal framing connector and rest, with i in. bearing, on the end posts. Connect any beams falling between in the same manner, but run them long over the tops of their posts. Stretch a chalkline from the ends of the two end beams across the interior beams and snap a line. Cutting the interior beams to length in this manner ensures a straight rim joist in the front.

Next, cut the rim joist to length. On a rect­angular deck, the rim joist is the same length as the ledger. If you have a long deck and use several pieces of rim, make sure they break over a post. The rim rests on the posts and is nailed into each beam with two 16d galvanized nails. Toenail both the beam and the rim to the post. Then reinforce the beam-post-rim joist connec­tions with metal framing connectors. You can nail a flat, gusset-type connector over the joint between a post and the rim joist and use right­angled connectors on the inside.

Before installing the joists between beams, make sure the post-and-beam assembly is parallel and square with the house and all the posts are plumb. Brace the porch frame so it will remain square until the stairs are attached and the decking is screwed in place. When cut­ting and installing joists, I recommend using joist hangers to ensure that all joist-to-beam connections are strong. The joist spacing you use depends on the decking material you plan to install. A 24-in. o. c. spacing is usually ade­quate for F/2-in.-thick PT decking boards. For 5/4 (F/4-in.-thick) PT decking, use 16-in. o. c. spacing. If you use any of the synthetic decking material that’s becoming more popular these days, follow the manufacturer’s recommenda­tions for joist spacing.

The corner post is crucial. Holding a long level against the flat sections of a turned post, a volun­teer makes sure the post is plumb.

STEP 2 INSTALL THE LEDGER

STAIR VOCABULARY

 

A stairway’s total rise is always from finish floor to finish floor.

 

CUT AND CLOSED STRINGERS

 

STEP 2 INSTALL THE LEDGERSTEP 2 INSTALL THE LEDGER

Подпись: Seven is the magic number. When determining the number and measurement of risers in a stairway, always start by dividing the total rise of the stair (the vertical distance from landing to landing) by 7. The unit rise (the height of each step) should be between 7 in. and 73/4 in.Подпись: LAYOUTOFA STAIR STRINGER 1. STRINGER LAYOUT Stair gauges set Plumb cut for 11-in. tread at bottom and 71/2-in. riser STEP 2 INSTALL THE LEDGERПодпись: 2. DROPPING THE STRINGERПодпись: 71/2-in. 6 in. STEP 2 INSTALL THE LEDGERПодпись: 3. NOTCHING FOR THE KICKER BOARDSTEP 2 INSTALL THE LEDGER

The Swedish Tjal2004

Tjal2004, developed by VTI, monitors temperature at every 50 mm down to a depth of 2 m. Temperatures are collected twice an hour and distributed via the Internet. The temperature sensors are calibrated to give highest possible accuracy close to 0°C where freezing starts. Trucks, having mobile Internet, pick up the current freezing situation from the installed Tjal2004 along the intended roads to travel. Road own­ers give truckers allowance to use roads as long as the upper part of the pavement is frozen down to a certain depth. This means that in spring, load restrictions are imposed and removed automatically and very frequently. During periods in spring with clear weather the situation might change daily. In the daytime the solar ra­diation thaws the upper layers, which is followed by re-freezing during the clear and cold night. This means that the heavy loading of trucks is allowed in the early morning but prohibited in the afternoon. Figure 8.13 shows typical repeated freezing and thawing during the period March 4 – April 22 of the year 2008 monitored by one of the Tjal2004 installed in Sweden. The total frost depth is close to 1.5 m.

8.2 Conclusions, Implications, Recommendations

Field observations indicate clear and significant variations of moisture in subgrades. This is true both for moderate climates as well as for cold regions where it is related to temperature. In particular, thawing may induce strong increases in moisture lev­els. The mechanical behaviour as observed in-situ is strongly affected by moisture variations: the wetter the state the lower the stiffness (up to a factor 2 or more), the lower the stiffness then the higher the deflection.

Therefore one may conclude that an efficient drainage system is crucial in order to reduce the road structure’s ageing. An analytical assessment of this relationship between moisture and mechanical performance will be undertaken in the following two chapters.

Venting Options

Until you expose the framing and actually run the pipe, it’s difficult to know exactly how things will fit together—especially vents. Because cor­rect venting is crucial, the section discusses sev­eral venting options to consider. But first, here are a few terms to keep straight: A stack is a verti­cal pipe. If the stack carries wastes, it’s a soil stack. If the stack admits air and never carries water, it’s a vent stack.

Most of the venting options described next are examples of dry venting, in which a vent stack never serves as a drain for another fixture. But there are hybrids; for example, if a vent stack occasionally drains fixtures above it, it is a wet vent. Wet vents must never carry soil wastes, and many local codes prohibit all wet venting. But when it’s legal and the vent is one pipe-size larger than normal to ensure a good flow, wet venting can be safe and cost effective because it requires fewer fittings and less pipe.

image580

No-hub couplings (also known as banded cou­plings, band-seal couplings, and hubless con­nectors) consist of an inner neoprene sleeve, which fits over the pipe ends or fittings, and an outer corrugated metal shield, which is drawn tight by a stainless-steel band clamp. No-hub couplings are widely used to join cast-iron pipe and no-hub fittings in new construction, but they are also invaluable to renovators.

For example, if you want to add a plastic shower drain to a cast-iron stack, no-hub cou­plings can accept either a cast-iron or a plastic no-hub fitting and seal it tightly to the pipe ends once you’ve cut into the stack. (Support both sides of the section to be cut out so it can’t shift during cutting and weaken other joints.)

When joining DWV pipes of different materi­als, use specialized transition couplings whose neoprene sleeves are sized for incoming pipes with different outside diameters, such as the coupling used to join 2-in. copper and 2-in. cast iron, shown in the photo at left.

BACK VENTING

Back venting (also known as continuous venting), is the dry-venting method shown below, and it’s acceptable to even the strictest codes. All the fix­tures in the drawing have a branch vent. In a typical installation, the trap arm of, say, a lava­tory empties into the middle leg of a sanitary tee. The branch drain descends from the lower leg; the branch vent from the upper. When a branch vent takes off from a relatively horizontal section of drainpipe, the angle at which it departs is crucial. It may go straight up, or it may leave at a 45° angle, to work around an obstruction. But it must never exit from the side of a drainpipe:

If it did, it could become clogged with waste.

image581

In this illustration of back venting, all fixtures have a dry branch vent—that is, no vent ever carries water. The fixtures on the first floor require a 2-in. branch vent because the toilet’s 3-in. drain needs more incoming air to equalize its large waste flow.

Maximum Distance: Trap Arm to Vent*

TRAP ARM MAXIUM DISTANCE DIAMETER (in.) TO VENT

M

2 ft. 6 in.

M

3 ft. 6 in.

2

5 ft.

3

6 ft.

4

10 ft.

* Also maximum distance of stack-vented fixture trap arm to stack, based on calculations found in the UPC, T10-1.

Branch vents must rise to a height of at least 42 in. above the floor before beginning their hori­zontal run to the vent stack. This measurement adds a safety margin of 6 in. above the height of the highest fixture (such as a sink set at 36 in.), so there is no danger of waste flowing into the vent. Since branch vents run to a vent stack, they should maintain an upward pitch of at least!4 in. per foot; although the UPC allows a vent to be level if it is 6 in. above the flood rim of a fixture.

STACK VENTING

Clustering plumbing fixtures around a central stack is probably the oldest method of venting. In the early days of indoor plumbing, plumbers noticed that fixtures near the stack retained the water in their traps; whereas those (unvented) that were at a distance did not. You can vent three bathroom fixtures (lavatory, tub, and toilet) off a 3-in. stack vent, without additional branch vents—if you detail it correctly, as shown in "Stack Venting,” above right.

Note: When stack venting, never place a toilet above the other fixtures on the stack: Its greater discharge could break the water seals in the traps of small-dimension pipes. If you must add fix­tures below those already stack vented, add (or extend) vent stacks and branch vents. The maxi­mum allowable distance from stack-vented fix­tures to the soil stack depends on the size of the pipe serving a particular fixture; see "Maximum Distance: Trap Arm to Vent,” above.

Подпись: I Venting a Toiletimage583Подпись: When there's plenty of space under a toilet—say, an unfinished basement— the branch drain can descend steeply.

Подпись: I Constricted Spaces
image584
Подпись: When a branch drain must travel through a floor platform before reaching a stack, the drain must slope gradually. Here, the angle the vent takes off from the toilet drain is critical—it must not be less than 45°, as depicted in the cross-section drawing at right.

STEP 1 COMPLETE THE ESSENTIAL ROOF FRAMING

In many house designs, a section of the main roof extends over the porch. To complete the
installation of the roof trusses, roofing material, and exterior trim, the truss support beams over the porch must be cut and fastened to the wall framing. As shown in the illustration above, each beam rests in a pocket formed by a pair of jack studs framed in the house wall. The top of the beam is flush and level with the top of the wall plates.

In addition to nailing the beam to the wall framing, I strengthen the connection by nailing an 18-in. metal strap across the top of the beam and the double top plate of the wall. Beams made from rough 2x lumber can

Подпись: Larger decks may require more bolts to attach the ledger to the house frame. You have to think about the weight a deck might carry—a party with 50 people on a deck is a lot of weight.
STEP 1 COMPLETE THE ESSENTIAL ROOF FRAMING

later be covered with aluminum cladding, as described in Chapter 6.

If it’s not possible to install permanent posts at this stage, temporary posts can be used to support porch ceiling beams. When you install perma­nent posts, be sure to secure them with framing connectors—a post base at the bottom and a post cap at the top that is fastened to the post and to the beams (see the photos above).

Monitoring Frost Depth and Thawing, Finland and Sweden

8.3.5.1 Introduction

Spring-thaw load restrictions are often imposed to avoid severe pavement deteriora­tion during periods of reduced bearing capacity. Equipment that enables monitoring of the pavement strength situation is very important for a road’s traffic carrying capacity, as restrictions could be lifted as soon as the pavement regains its capacity. There are projects with this aim being run in both Sweden and Finland. In Finland the Percostation is used to monitor dielectric value, electrical conductivity and tem­perature with depth. The Swedish approach is to monitor temperature profile only and to distribute this via the Internet enabling direct access from trucks to frost depth readings that are updated twice an hour. Both approaches are now described.

8.3.5.2 The Finnish Percostation

The Percostation monitors dielectric value, electrical conductivity and temperature at different depths through a maximum of eight channels. Both dielectric value and electrical conductivity are sensitive to the amount of unfrozen water, that is, it is clearly indicated when water freezes and when ice melts. Temperature is, of course, also related to freezing and thawing. Figure 8.12 shows dielectric values at depths 0.15 and 0.30 m together with air temperature during the thawing period of the year 2000 at the Koskenkyla Percostation. From the figure it is clear that the dielectric value approximately equals 5 at both depths when the soil is frozen and that it in­creases at thawing.

Fig. 8.12 Dielectric values and air temperature monitored by the Koskenkyla Percostation during spring 2000 (Saarenketo et al., 2002). Reproduced by permission of T. Saarenketo

The increase starts at depth 0.15 m and is somewhat delayed at the lower depth as thawing takes place from the surface and downwards. In late spring the dielectric value is highest at the greater depth indicating higher frost susceptibility and higher amount of ice lenses melting. Around April 10-12 the dielectric values show a peak followed by a continuously ongoing decrease when surplus water drains and bearing capacity recovers. The data monitored by the Percostation is of great value when imposing and removing spring-thaw load restrictions.

Problems

As with other asphalt mixtures, problems frequently occur with SMA, too. They may develop at the stage of design, production, or application. Some of the troubles described here also appear in asphaltic concrete or other asphalt mixtures, but a dis­tinctive feature of SMA is that its shortcomings are revealed in a particularly clear, and sometimes painful, way.

This chapter presents an arranged collection of the most common defects observed in SMA. But before we begin, two issues need to be made clear:

• Each group of problems and their probable causes are provided here based on the author’s subjective assessment derived from his experience and con­sideration. Therefore it is obvious that a reader may have a different view on a given problem or that it may have another cause.

• Always and in each case, while examining a detected problem, one should be open to investigating its various causes, including the less obvious ones. Nobody should limit himself or herself to the pieces of advice contained in this book; an open mind is the recommended approach.

An immediate “blessing” when a problem occurs is having a laboratory or pos­sibly the asphalt plant staff available to help correct the problem; these resources are becoming more widely available. The lab or plant staff can help to evaluate the materials and operations to identify the causes of the problems, such as changes in material properties, plant temperatures, moisture conditions, etc. This chapter will make it apparent that the members of the team preparing road machines and the site team are as important in the final outcome (success or failure) as other elements.[65]

Now it is time to examine with the problems in detail.