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DETERMINATION OF SPAN LENGTHS

Posted by admin on 17/ 11/ 15

Where the spans are not controlled by features crossed—such as roads, railroads, streams, or existing buildings—and there is freedom to locate piers, the lengths of spans will be controlled by aesthetic, economic, and structural requirements. Generally, from an aesthetic standpoint, spans should have a length at least 3 or 4 times the pier height.

The profile of the site crossed will influence the span proportions. On the uphill end of a crossed hillside, the end spans will be shorter than at the bottom of the valley. The type of bridge will also affect the selection of span ratios, from both aesthetic and structural standpoints. Where spans are continuous, the end span should not be made too short, because uplift may occur under live load, and loss of positive reaction at the abutment will occur sooner if the abutment settles.

The most economical bridge will generally not be either the one with the most economical superstructure or the one with the most economical substructure, but the one with the least combined cost. That determination is made by performing a cost study wherein a number of different span lengths are investigated, along with the cost of their substructures. To be meaningful, the superstructure and substructure designs should be fairly detailed. The superstructure and substructure costs are then plotted. The optimum span length will be at the low point of the combined cost curve. A typical cost study curve is shown in Fig. 4.11.

FRAMING A DOOR OR WINDOW OPENING

Posted by admin on 17/ 11/ 15

After cutting back interior surfaces to expose the framing in the exterior wall, outline the RO by snapping chalklines across the edges of studs. If you can incorporate existing studs into the new opening—an old stud might become the king stud of the new opening, as shown in the photo on p. 165—you can save time and materials.

To remove old studs within the new opening, use a sledge to rap the bearing wall’s top plate upward, thus creating a small gap above the studs (and old header, if any). That should create enough space to slip in a metal-cutting reciprocating-saw blade and cut through nails holding studs to the top plate. Though sheathing or siding may be nailed to the studs, they should still pull out easily.

Start framing the new opening by toenailing the king stud on both sides, using three 10d nails or four 8d nails top and bottom. Laminate the header package or cut it from 4x stock. (The procedures described here employ terms illustrated in "Stud-Wall Elements,” on p. 155.) Precut the jack studs, and face-nail one to a king stud; lean the second near the other side of the opening. Place one end of the header atop the jack stud in place. Then slide the second jack under the free end of the header. Raise the header by tapping the second jack into place. Or, as an alternative, you can use a screw jack to hold the header flush to the underside of the top plate. Check for level; then measure and cut both jack studs to length.

If there are cripple studs over the header, nail up one jack stud, use a level to establish the height of the jack stud on the second side, and nail it up. Install the header; then cut the cripple studs to length and install them. If you’re framing a window opening, there will also be cripple studs under the sill. So level and install the sill next, using four 8d nails on both sides for toenailing the sill ends to the jack studs. End-nail through the sill into the top of the cripple studs; toenail the bottoms of the cripple studs to the sole plate.

To mark the rough opening outside, cut

through the sheathing and the siding, using a reciprocating saw. Or, if you want to strip most of the siding in the affected area first, drill a hole

is it a Bearing wall?

As noted in "Exploring Your Options," on p. 152, bearing walls and girders usually run parallel to the roof ridge and perpendicular to the joists and rafters they support. And in most two-story houses, joists usually run in the same direction from floor to floor.

Things get tricky, however, when rooms have been added piecemeal and when previous remodelers used nonstandard framing methods. For that, you’ll need to explore. Use an electronic stud-finder or note which way the heating ducts run (usually between joists) to figure out joist direction. If all else fails, go into a closet, pantry, or other inconspicuous location and cut a small hole in the ceiling so you can see which way the joists run.

Finally, nonbearing walls sometimes become bearing walls when homeowners place heavy furniture, book shelves, appliances, or tubs above them. If floors deflect—slope downward—noticeably toward the base of such walls, they’re probably bearing.

through each corner of the RO. Outside, snap chalklines through the four holes. Remove siding within that opening—plus the width of the new exterior casing around all four sides. Nail the sheathing to the edges of the new frame. Finally, run a reciprocating saw along the chalklines to cut sheathing flush to the edges of the RO. Now you’re ready to flash the opening and install the door or window. Chapter 6 will guide you from there.

REPLACING A BEARING WALL

Bearing-wall replacements should be designed by a structural engineer and executed by a contractor adept at erecting shoring and handling heavy loads in tight spaces. In the two methods presented in the following text, beam-and-post systems replace bearing stud walls. In the first method, the bearing beam is exposed because it supports joists from below. In the second method, the beam is hidden in the ceiling, and joist hangers attach joists to the beam.

О Once you’ve cut electrical power to the affected area, installed shoring on both sides of the existing bearing wall, and inserted blocking under support post locations, you’re ready to remove the bearing wall and replace it with a new beam. However, if you’re installing a hidden beam, your job will be easier if you leave the old

wall in place a bit longer to steady the joist ends as you cut through them.

Installing an exposed beam is the easier of the two methods. Because ceiling joists sit atop an exposed beam, it’s not necessary to cut the joists—as it is when installing a hidden beam. After removing the bearing wall, snap chalklines on the ceiling to indicate the width of the new beam—say, 4h in. wide for a beam laminated from three 2x10s or 2x12s. Cut out the finish surfaces within this 4h-in.-wide slot so the joists can sit directly on the beam. Chances are, the slot won’t need to be much wider than the width of the top plate of the wall just removed.

Because the beam extends into end walls, notch the beam ends so they will fit under the end-wall top plates, which may also support joists. Notching ensures that the top of the beam, the top plates, and the bottom of the ceiling joists will be the same height. If end walls have doubled top plates, the notch will be 3 in. to 4 in. deep. Before notching the beam, eyeball it for crown and place it crown up. Before raising the beam, be sure to have blocking under each post to ensure a continuous load path down to the foundation.

A laminated 2×12 beam can weigh 250 lb., so have enough helpers to raise it safely. Once the top of the beam is in place, flush to the underside of the joists above, temporarily support it with plumbed screw jacks or 2x4s cut % in. long and wedged beneath the beam—have workers tack- nail and monitor the 2x4s so they can’t kick out! (Put 2x plates beneath the jacks or the wedged 2x4s to avoid damaging finish flooring.)

Measure from the underside of the new exposed beam to the floor or subfloor. Then cut 4×4 posts Яв in. longer than the height of the opening, and use a sledgehammer to tap them into place. (Ideally, cut posts the exact length; but a little long is preferable to a little short.) Plumb the posts, and install metal connectors such as Simpson Strong-Tie A-23 anchors to secure the post ends to the top and sole plates. Add studs to both sides of each post, as shown in "Supporting an Exposed Beam,” to "capture” it and keep it from moving; nail these studs to the plates and to the 4x4s as well.

Подпись: After notching and then raising an exposed beam with jacks, cut 4x4 posts to support it at both ends. There must also be blocking under each post, to transfer post loads to the girder and other foundation elements. Installing a hidden beam takes more work than installing an exposed beam but yields a smooth ceiling. To summarize, after erecting stud-wall shoring on both sides of the bearing wall to be replaced, cut all the ceiling joists to create a slot for the hidden beam, assemble the beam on the ground, and then lift it into place. Here, joists will hang from the sides of the beam rather than

Подпись: A hidden beam allows you to remove a bearing wall and still have a smooth expanse of ceiling. A continuous load path—from the beam, through the posts, to the foundation—is crucial to a successful installation.

sitting atop it, so the hidden beam will rest on top of end-wall top plates.

Thus install 4×4 posts between the top and the sole plates—and blocking under the posts— before raising the beam. Snap chalklines on the ceiling to indicate the width of the beam plus 4 in. extra on each side so you can slide joist hangers in later. Cut out drywall or plaster within that slot to open up the ceiling and expose joists. After installing shoring, as explained in earlier sections, go up into the attic.

1. Make the attic workspace safe and comfortable. Place 2-in.-thick planks or 58-in. plywood walkways on both sides of the area where you’ll insert the beam. Tack-nail the walkways so they can’t drift. Clamp work lights to the underside of rafters and add ventilation. For necessary ventilation, you may first need to install gable end louvers and buy a fan—especially if it’s summer. If roofing nails protrude from the underside of roof sheathing, wear a hard hat.

If there’s enough room in the attic, assemble the beam in place and lower it down into the slot you’ll create by cutting back joist ends. However, if you must assemble the beam on the floor below—or if you’re raising an engineered beam— use a nylon web sling and a chain fall (see the photo on p. 53) bolted through the rafters to raise the beam up through the cutout in the ceiling. Angle-brace rafters to keep them from deflecting under the load, and don’t attach a chain fall to rafters that are cracked or already sagging.

2. Snap a chalkline to mark the beam location onto the top edges of joists. Snap a first line to mark the centerline of the beam. Then measure out half the beam width plus 58 in. on both sides, and snap chalklines to indicate cut-lines on the joists. Using a square, extend these lines down the face of each joist. Use vivid chalk so the marks will be visible.

Because thin reciprocating-saw blades wander, use a circular saw to ensure square cuts across joists. It’s hard to see the cut-line of a saw you’re lowering between two joists, so clamp a framing square to each joist to act as a guide for the saw shoe. Some renovators prefer a small chainsaw for this operation, but hitting a single hidden nail in a joist can snap a chainsaw blade and send it flying at you. Whatever you use to cut the joists, wear hearing and eye protection and, ideally, have a similarly protected helper nearby shining a light into the cut area.

3. Get help to raise the beam one end at a time. If your cuts are accurate, you should be able to raise the beam between the severed joists and onto the top plate of one end wall and then the other. But, invariably, the beam gets hung up on something. Here, a chain fall is invaluable because it allows you to raise and lower one end of the beam numerous times without killing your back or exhausting your crew.

When the first end of the beam is up, nail cleats to both sides of the beam so it can’t slip back through the opening as you raise the other end. Raise and position the other end of the beam atop the other end wall and directly over

Подпись: Before attaching joist hangers, make a single pass of a power plane across the underside of each joist end, where it abuts the new beam. The planed area, roughly the width and thickness of a joist hanger "stirrup," ensures that the joist hangers will be flush to the bottom of the joists and the beam and that the patched ceiling will be evenly flat.

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Heavy Metal

Steel connectors are an important part of renovation carpentry, often joining new and old framing members.

Straps such as Simpson Strong – Tie LSTA strap ties are frequently used where wall plates are cut, at wall intersections, and as ridge ties.

Pros often use them to splice new rafter tails to existing rafters, to replace sections that rotted at the wall plate. After cutting rafter tails at the correct angle, toenail them to the top plate and use 12-in. or 18-in. strap ties to tie new tails to the old rafters. After the sheathing is nailed on, such reinforced rafter tails will stay in line indefinitely.

The 4×14 Parallam beam sitting atop a 2×4 top plate at right is much like the hidden beam discussed in "Installing a Hidden Beam" in the text. In the old days, beams of this size would have been merely toenailed to top plates.

So the Simpson BC4 post cap now specified by engineers is quite an improvement. It’s simple to install and strong enough to resist uplift and lateral movement. Note, too, the 4×4 post directly under the beam—it’s part of the load path that goes all the way down to the foundation.

Brief history of the Hellenistic kingdoms and their successors1

Posted by admin on 17/ 11/ 15

Setting out from Macedonia, with contingents of Macedonian and Greek soldiers, Alexander achieved a first victory over the Achaemenid King Darius II, who ruled the Persian Empire, at the battle of Issus. Egypt falls without resistance into the clutches of Alexander, who makes a long sojourn there from 332-331 BC. During this sojourn, he founds Alexandria on the seafront, an ideal site for the development of commerce, lying [163] between the sea and a lagoon. But the site is poorly supplied with fresh water, being some distance from the Nile. Considerable engineering efforts are undertaken to support the burgeoning activity of the city (Figure 5.2). These include a kilometer-long dike (hepstastade) to link the island of Pharos to the coast, a 30-km canal to bring fresh water from the Nile, and numerous cisterns to store this water. Later a lighthouse is built to guide maritime navigators along this low-lying and dangerous coast. [164]

Brief history of the Hellenistic kingdoms and their successors1

Figure 5.2 The city of Alexandria and the harbor works described by Strabo who visited it around 25 AD. “The point of the island is a rock assailed by the waves on all sides and supporting a tower made of white stone, admirably constructed, having several levels, and having the same name as the island. Sostrate of Cnide, a friend of the king’s, dedicated it as a salute to navigators, as shown on its inscription. [….] The opening to the West [.] forms a second port, that of Eunostos, which sits opposite the closed and artificial port. The port whose entry is next to the tower of Pharos, mentioned above, is the major harbor; two others are contiguous to it at the back of the bay, separated from the main port by the Heptastade dike. The dike forms a kind of bridge […] with two open passages. [….] This dike actually served as both a bridge and an aqueduct, during the period when Pharos was inhabited. […] The city has many advantages. First, the location touches two seas, to the north the Egyptian sea, as it is called, and to the south by the Mareia Lake, also called lake Mareotis. This lake is fed on its upper boundary and sides by numerous canals coming from the Nile. […]. When leaving by the Canopic gate, one sees to the right the Canal, which connects the Lake and Canope.” (Geography, XVII, 1 6-7 and 16).2

Leaving Alexandria, the conqueror succeeds in completely destroying the Persian Empire through a decisive victory, and pushes on to the Indus. He dies an early death at Babylon in 323 BC, before having solidified his Empire. Indeed, his generals divide up – and fight over – the elements of that Empire. The Macedonian Ptolemy, son of Lagos, founds the dynasty of the Lagides in Egypt. Lysimachus receives Thrace. Seleucos obtains Babylonia several years later, and then Syria. But his family line, the Seleucids, only intermittently govern lower Mesopotamia, as it is fought over by other powers such as the Parthes, who progressively push the Seleucids toward Syria. New kingdoms of Hellinistic culture appear to the north of the empire of the Seleucids, along the Black Sea: Pontus, Bithynia, and Cappadocia. The power of the city of Pergamon, initially just a simple fortress, increases in Asia Minor and it becomes a dependency of the Seleucids from about 282 to 260 BC, capital of an increasingly powerful empire. From 260 BC, the influence of Pergamon becomes comparable to that of Alexandria.

The Seleucids are conquered by the Romans, allied with Pergamon, in 189 BC. In 133 BC the last king of Pergamon bequeaths his kingdom to Rome. From the middle of the 2nd century BC, a certain decadence of the Lagide Dynasty sets in, including economic difficulties and revolts. With the death of Cleopatra, in 31 BC, Egypt in its turn falls under the control of the Roman Empire.

Exterior Foam Is a Good Option

Posted by admin on 17/ 11/ 15

Adding exterior foam to walls works well for new construction. As long as you meet local wind and earthquake codes, it’s usually possible to build a foam-sheathed wall without structural oriented strand board (OSB) or plywood sheathing. Foam-sheathed walls are braced using one of four methods:

• Diagonal 1×4 let-in braces.

• Diagonal T-profile steel strapping, such as Simpson TWB.

• Inset shear panels.

• A few strategically placed pieces of OSB (they are usually installed at corners).

Of course, you should check with an engineer and your local building official before finalizing your wall-bracing plan.

Exterior foam sheathing is often installed on existing homes as an energy-saving

retrofit when new roofing or siding is needed. You can install rigid foam on the inside of a wall as well, but adding exterior foam increases the R-value of a wall or roof without eating up interior living space.

Installed on the roof, exterior foam makes the living space below more comfortable and reduces the likelihood of ice dams.

The illustration on the facing page shows two layers of OSB or plywood roof sheathing: a lower layer conventionally nailed to the rafters and an upper layer installed as a nailing surface for the roofing material on top of the rigid foam. The type of fasteners used and the way they need to be spaced for the top layer of sheathing depend on the pitch of the roof and roof loads, particularly wind and snow loads. It’s fairly easy to find screws with a pullout-resistance rating exceeding 400 lb., even when they are secured just to plywood or OSB sheathing. The fastener rating increases if the screws are driven into the rafters. (Fastener sources include Wind-lock® and FastenMaster®, which manufactures HeadLok® and OlyLog® screws.)

Most foam-sheathed walls include a rain – screen gap between the foam and the siding. After the foam is tacked in place temporarily with a few nails, it is secured in place with vertical 1×3 or 1×4 strapping that is screwed through the foam to the underlying studs. Some siding types, including cedar shingles, may require a drainage mat, kerfed horizontal furring, or an OSB or plywood nailer over the foam.

Does Exterior Foam Create a Wrong-Side Vapor Barrier?

Some builders worry that exterior foam sheathing is a "wrong-side vapor barrier" that can trap moisture in walls. In new construction without interior polyethylene vapor barriers, the worry is baseless. As long as the foam sheathing is thick enough, it will reduce the chance that moisture will accumulate in a wall. By warming the wall cavity, exterior foam eliminates cold surfaces where moisture can condense. Here are the minimum R-values for exterior foam for 2×6 walls:

• R-15 in climate zones 7 and 8

• R-11.25 in climate zone 6

• R-7.5 in climate zone 5

• R-3.75 in climate zone 4

When exterior rigid foam is used as an energy-saving detail in warmer climates, condensation is not a concern, so no minimum R-values apply.

Since exterior foam reduces a wall’s ability to dry to the exterior, foam-sheathed walls should be able to dry to the interior. That means that foam-sheathed walls should never include interior polyethylene or vinyl wallpaper. Painted drywall has a high enough permeance to allow any incidental moisture that enters a wall cavity in the winter to evaporate through the drywall during the summer.

If you are considering installing exterior foam on a house with interior 6-mil polyethylene, proceed with caution. If water ever enters a wall with foam sheathing and interior poly, the wall has a very limited ability to dry. This raises the stakes, and water – management details must be impeccable.

After all the siding has been removed, inspect the existing wall sheathing for stains or moisture damage. If you find either, you’ll need to diagnose the cause and implement remedies. If the existing sheathing is clean, dry, and sound, it’s safe to install exterior wall foam, as long as the new siding is installed with a rain-screen gap and meticulous flashing.

Martin Holladay is a contributing editor to Fine Homebuilding.

Using Rigid Foam for an Efficient and Dry House 81

COMMON TRUSSES FOR GABLED ROOFS

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COMMON TRUSSES FOR GABLED ROOFS

Подпись: Delivery right on the walls. It saves time and energy to have the truss company deliver the trusses and lay them right on the top plate of the framed walls. [Photo © Elmer Griggs]

be open or closed. For details on different ways to finish off an eave, see the sidebar on p. 117. NUMBER OF TRUSSES. Roof trusses are typically spaced 24 in. o. c. Therefore, if your building is 40 ft. long, you’ll need to order 21 trusses. Two of the trusses will be for the gable ends. These trusses have studs rather than webbing to receive the exterior wall covering. SPECIAL REQUIREMENTS. If your house has a more complex roof, special trusses may be required where one roof section joins another. Often houses are built in a “T” or “L” shape or have a side porch that connects to the main roof. You can cut the rafters needed to tie the porch roof to the main roof. Another option is to have the truss builder look at the plans, check the span of these trusses, and build to your specifications.

ROOF PITCH. Trusses for most small affordable buildings have either a 4-in-12 or a 5-in-12 pitch (see the illustration on the facing page).

STEP 1 PREPARE FOR TRUSS ARRIVAL AND INSTALLATION

Подпись: Get set for bracing. Before you begin to install roof trusses, have plenty of bracing boards on hand. You'll need some 16-ft. 1x4s to nail across rafters, plus a good supply of 2x4s for sway and other braces.

When roof trusses are delivered to a job site, they can be offloaded onto the ground or onto the framed walls of the building (see the photo on p. 115). The choice depends on the builder’s preference and on the delivery truck’s capabilities. Experienced builders prefer delivery on the walls because it saves time. Trusses can be long and cumbersome. Putting them up on walls by hand can be difficult, dangerous, and time consuming. Most truss builders deliver the trusses on a boom truck. The boom can be used to set all the trusses directly on the walls. Plan ahead and order truss delivery the day after all the walls are framed and braced.

Whether your trusses are offloaded onto the walls or onto the ground, they need to lie flat.

I have seen trusses that were stored on uneven ground come apart at the seams, making them useless within a couple of weeks. Until they are nailed upright in place, braced, and sheathed, trusses are actually quite fragile. Prepare a flat area close to the house where the trusses can be offloaded. The bottom-most truss should not rest directly on the ground but on wood stickers that provide a flat, level base.

Set up work platforms

One of the most difficult parts of roof-truss installation is working high off the ground. It takes skill and practice to be able to stand on a narrow top plate and nail trusses to the wall. If this seems dangerous, or if you’re uncomfortable with it, try working on a ladder or a scaffold instead. To make it easy to move trusses into position, I like to build a catwalk, or walkway, over open sections, such as the living room. (For directions on how to erect a catwalk, see the illustration on p. 118.)

Mark truss locations

Before trusses arrive on the job site, take some time to lay out their locations on the top of the wall plates. Hook a long tape on the end of the

DRAINDOWN TESTING

Posted by admin on 16/ 11/ 15

The draindown effect is the process of the separation of liquid binder or mastic from an SMA mixture that occurs at a high temperature when the binder is still molten.

Both the binder and the mastic can separate. It is common knowledge that SMA mixes are marked by an intentional excess of binder, and the draindown effect is caused by the impossibility of maintaining such an excess of binder on grains of aggregate. That problem is most frequently solved by adding a stabilizer (or drainage inhibitor) to a mix. Its task is to absorb any excess of binder.

Excessive draindown may be caused by several factors (as described in Chapter 4). Binder or mastic draindown from a mix brings about many problems; most of them are described in Chapter 11.

Research on an SMA mix’s susceptibility to binder or mastic segregation has been conducted in virtually all the countries using this type of mix. A short review of the procedures of draindown testing and the regulations for the following methods will be discussed later:

• Using Schellenberg’s method (the original German method)

• Using the European standard EN 12697-18

• Using the U. S. standard AASHTO T 305-97

STORM-WATER CALCULATIONS

Posted by admin on 16/ 11/ 15

Подпись: ✓ fast code fact Journeyman plumbers are not normally required to know how to figure roof drains and major storm-water calculations. This is typically the job of a master plumber. Of course, circumstances vary from location to location, so the process is well worth learning at any level in your plumbing career. Storm-water calculations stump some plumbers. I think that the problem for some plumbers is computing the amount of water accumulated due to structures on roofs. For example, if a roof has an enclosed stairway system, the walls and roof of the stairway have to be factored into the equation for what is required in rainfall drainage. Some plumbers find doing the math for roof drains, rain leaders, and other storm piping to be intimidating. Given the proper charts and tables, the job is not really too difficult.

Подпись: been there done that Don’t allow the code requirements to scare you. I remember the first time I had to pipe an island sink. It made me very uncomfortable, even though there was a diagram in the codebook on how to do the job. What may seem daunting when you first look at the code is not necessarily such a mess. Trust in yourself. I used to teach code classes for plumbers who were preparing to take their licensing tests. After teaching the class for a while, I noticed some common elements from class to class. One common thread that seemed to run from class to class was a fear of doing storm-water calculations. I came to expect the classes to be intimidated by what I didn’t perceive to be any big deal. Knowing how to size a drainage system for storm water is a requirement for licensing where I live and work, so the people in the class had to address their fears. This, however, was true only of those going for their master’s license. Oddly enough, once they were given an example or two of how the work is done, most of them didn’t have any problem with their calculations.

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STORM-WATER CALCULATIONS

FIGURE 6.1 ■ Rainwater code requirements. (Courtesy of Uniform Plumbing Code)

I could create some examples for you to work with here, but I won’t. Why? Because two of the major codes already offer sample exercises in their codebooks, and the two codes have agreed to allow me to use their examples for this chapter’s tutorial. So, what I’m going to do is show you actual excerpts from two codebooks. One of the codes is the Uniform Plumbing Code. The other is the Standard Plumbing Code, or as some people call it, the Southern Plumbing Code. I will let you look over the examples, one at a time, and then I will comment on them, pointing out some of the areas that may appear a little tricky. Let’s start with the example provided in the Uniform Plumbing Code. Please refer to Figures 6.1 through 6.8 for code requirements and a sizing example for rainwater systems. I want you to keep in mind that books age

(c) Roof drains, overflow drains, and rainwater piping installed within the construction of the building shall be tested in conformity with the provisions of this Code for testing drain, waste, and vent systems.

Part В
Roof Drains

A 2 Materials: Roof drains shall be of cast iron, copper, lead, or other corrosion resisting material.

A 2.1 Strainers:

(a) Roof drains shall be equipped with strainers extending not less than four (4) inches (101.6 mm) above the surface of the roof immediately adjacent to the drain. Strainers shall have minimum inlet area one and one-half (IV2) times the pipe to which it is connected.

(b) Roof deck strainers for use on sun decks, parking decks, and similar occupied areas may be of an approved flat-surface type which is level with the deck. Such drains shall have an inlet area not less than two (2) times the area of the pipe to which the drain is connected.

(c) Roof drains passing through the roof into the interior of a building shall be made watertight at the roof line by the use of a suitable flashing material.

PartC

Sizing of Rainwater Piping

A 3.1 Vertical rainwater piping shall be sized in accordance with Fig. 8.3. Figure 8.3 is based upon maximum inches (mm) of rainfall per hour falling upon a given roof area in square feet (m2). Consult local rainfall figures to determine maximum rainfall per hour.

A 3.2 Vertical Wall Areas. Where vertical walls project above a roof so as to permit storm water to drain to the roof area below the adjacent roof area may be computed from Fig. 8.3 as follows:

(a) For one (1) wall—add fifty (50) percent of the wall area to the roof area figures.

(b) For two (2) adjacent walls—add thirty-five (35) percent of the total wall areas.

(d) Two (2) walls opposite of differing heights—add fifty (50) percent of wall area above top of lower wall.

(e) Walls on three (3) sides—add fifty (50) percent of area of the inner wall below the top of the lowest wall, plus allowance for area of wall above top of lowest wall per (b) and (d).

(f) Walls on four (4) sides—no allowance for all areas below top of lowest wall – add for areas above top of lowest wall per (a), (b), (d), and (e).

FIGURE 6.2 ■ Rainwater code requirements. (Courtesy of Uniform Plumbing Code)

and the illustrations here may not be up to speed with your current, local code. Check you own code requirements and use the tables here as examples of how to use what you have.

Now that you’ve had a chance to look over the illustrations, you may have a solid understanding of how to size a rainwater system. If you do, that’s great. But, maybe you have a little confusion that needs to be cleared up. Let me go over a few of the points that some plumbers from my classes have had trouble with. Start by looking at Figure 6.2, part C. In category A 3.2 of Figure 6.2, I want you to look at letter A. The code tells you to figure 50 percent of

a single wall for additional rainwater. So, if the wall is 10 feet long and 10 feet tall, its total area would be 100 square feet. This is determined by multiplying the width by the height. In this case, we would add 50 square feet of area to our working numbers to apply to the sizing chart.

Now look at the ruling in letter B. It says that if you have two adjacent walls, you must add 35-percent of their combined area to the equation.

Sizing of Roof Drains and Rainwater Piping for Varying Rainfall Quantities are Horizontal Projected Roof Areas in Square Feet

Rain fall		Size of drain or	leader in	inches*
in inches	2	3	4	5	6	8
1	2880	8800	18400	34600	54000	116000
2	1440	4400	9200	17300	27000	58000
3	960	2930	6130	11530	17995	38660
4	720	2200	4600	8650	13500	29000
5	575	1760	3680	6920	10800	23200
6	480	1470	3070	5765	9000	19315
7	410	1260	2630	4945	7715	16570
8	360	1100	2300	4325	6750	14500
9	320	980	2045	3845	6000	12890
10	290	880	1840	3460	5400	11600
11	260	800	1675	3145	4910	10545
12	240	730	1530	2880	4500	9660

_ . . Size of drain or leader in millimeters*

in mm	50.8	76.2	101.6	127	152.4	203.2
25.4	267.6	817.5	1709.4	3214.3	5016.6	10776.4
50.8	133.8	408.8	854.7	1607.2	2508.3	5388.2
76.2	89.2	272.2	569.5	1071,1	1671.7	3591.5
101.6	66.9	204.4	427.3	803.6	1254.2	2694.1
127	53.4	163.5	341.8	642.9	1003.3	2155.3
152.4	44.6	136.6	285.2	535.6	836.1	1794.4
177.8	38.1	117.1	244.3	459.4	716.7	1539.4
203.2	33.4	102.2	213.7	401.8	627.1	1347.1
228.6	29.7	91	190	357.2	557.4	1197.5
254	26.9	81.8	170.9	321.4	501.7	1077.6
279.4	24.2	74.3	155.6	292.2	456.1	979.6
304.8	22.3	67.8	142.1	267.6	418.1	897.4

Подпись: A 3.3 Horizontal Rainwater Piping. The size of a building rainwater piping or any of its horizontal branches shall be sized in accordance with Figs. 8,5 and 8.6 (based upon maximum roof areas to be drained). Example: Figs. 8.5 and 8.6 Roof Area —5900 sq. ft. (548.1 m2) Max. Rainfall/hr. —5 inches (127 mm) Pipe Laid at Vi" (20.9 mm/m) slope Find roof area in column under 5" (127 mm) rainfall (6040 sq. ft. (561.1 m2) is closest), read 6" (152.4 mm) as size of piping in left hand column. A 3.4 Roof Gutter. The size of semi-circular roof gutters shall be based on the maximum roof area, in accordance with Figs. 8.7 and 8.8.

Подпись: Example: Figs. 8.7 and 8.8 Roof Area—2000 sq. ft. (186 m2) Max. Rainfall/hr.—4" (101.6 mm) Gutter set at Vs" (10.4 mm/m) slope Find roof area in column under 4" (101.6 mm) rainfall 1950 sq. ft. (181.4 m2) is closest), read 7" (177.8 mm) diameter gutter in left hand column. A 3.5 If the rainfall is more or less than those shown in Figs. 8.5-8.8, then adjust the figures in the 2" (50.8 mm) rainfall column by multiplying by two (2) and dividing by the maximum rate of rainfall in inches/hr. (mm/hour). Example: In Figs. 8.5 and 8,6 with an Ve" (10.4 mm/m) slope and an 8" (203.2 mm) rainfall, find the number of square feet (m2) a 4" (101,6 mm) pipe will carry. 2 X 3760 „ = 940 sq. ft. (87.4 m2)

Assuming that each wall was 10 feet by 10 feet, we would have a total of 200 square feet. 35 percent of 200 square feet is 70 square feet. See how easy this is? In the rulings identified by the letter C, you can see that no additional square footage is added when you have two walls that are opposite of each other and that are the same size. But, letter D offers another ruling. Assume that you have two walls opposite of each other. one of the walls is 10 feet by 10 feet. The other is 10 feet by 15 feet. How much area do you add? One wall is 5 feet taller than the other and 10 feet wide. This amounts to a total area of 50 square feet in differing size for computation purposes. Now all you have to do is divide the difference in half for your working number, which in this case would be 25 square feet. If you pay attention, the code does most of the work for you.

Size of Horizontal Rainwater Piping

Size of pipe in mm 10.4 mm/m slope	Maximum rainfall	in millimeters per	hour
50.8	76.2	101.6	127	152.4
76.2	152.7	101.8	76.4	61	50.9
101.6	349.3	232.8	174.7	139.7	116.4
127	620.6	413.7	310.3	248.2	206.9
152.4	994	662.7	497	397.6	331.3
203.2	2136.7	1424.2	1068.4	854.7	706
254	3846.1	2564	1923	1540.3	1282
279.4	6187.1	4124.8	3093.6	2475.8	2062.4
381	10126.1	6763.1	5527.6	4422	3683.5

Size of pipe in mm 20.9 mm/m slope	Maximum rainfall in millimeters per hour
50.8	76.2	101.6	127	152.4
76.2	215.5	143.6	107.8	86.2	71.8
101.6	492.4	328.2	246.2	197	164.1
127	877	584.1	438.5	350.8	292.3
152.4	1402.8	935.1	701.4	561.1	467.6
203.2	3028.5	2019	1514.3	1211.4	1009.5
254	5425.4	3618.5	2712.7	2169.2	1806.9
304.8	8732.6	5815.5	4366.3	3493	2912.4
381	15607.2	10404.8	7803.6	6247.5	5205.4

Size of pipe in mm 41.7 mm/m slope	Maximum rainfall	in millimeters per hour
50.8	76.2	101.6	127	152.4
76.2	305.5	213.2	152.7	121.7	101.8
101.6	698.6	465.4	349.3	279.6	232.3
127	1241.1	826.8	620.6	494.2	413.4
152.4	1988.1	1272.3	994	797.1	663.3
203.2	4274.4	2847.4	2136.7	1709.4	1423.2
254	7692.1	5128.1	3846.1	3079.6	2564
304.8	12374.3	8249.5	6187.1	4942.3	4124.8
381	22110.2	14752.5	11055.1	8853.4	7362.3

Size of Gutters

Maximum rainfall in inches per hour

Уїв" slope	2	3	4	5	6
3	340	226	170	136	113
4	720	480	*360	288	240
5	1250	834	625	500	416
6	1920	1280	960	768	640
7	2760	1840	1380	1100	918
8	3980	2655	1990	1590	1325
10	7200	4800	3600	2880	2400
Diameter of gutter Vb" slope	Maximum rainfall in inches per	hour
2	3	4	5	6
3	480	320	240	192	160
4	1020	681	510	408	340
5	1760	1172	880	704	587
6	2720	1815	1360	1085	905
7	3900	2600	1950	1560	1300
8	5600	3740	2800	2240	1870
10	10200	6800	5100	4080	3400
Diameter of gutter slope	Maximum rainfall in inches per	hour
2	3	4	5	6
3	680	454	340	272	226
4	1440	960	720	576	480
5	2500	1668	1250	1000	834
6	3840	2560	1920	1536	1280
7	5520	3680	2760	2205	1840
8	7960	5310	3980	3180	2655
10	14400	9600	7200	5750	4800
Diameter of gutter W slope	Maximum rainfall in inches per	hour
2	3	4	5	6
3	960	640	480	384	320
4	2040	1360	1020	816	680
5	3540	2360	1770	1415	1180
6	5540	3695	2770	2220	1850
7	7800	5200	3900	3120	2600
8	11200	7460	5600	4480	3730
10	20000	13330	10000	8000	6660

Size of Gutters

Diameter of gutter 20.9 mm/m slope	Maximum rainfall	in millimeters per hour
50.8	76.2	101.6	127	152.4
76.2	63.2	42.2	31.6	25.3	21
101.6	133.8	89.2	66.9	53.5	44.6
127	232.3	155	116.1	92.9	77.5
152.4	356.7	237.8	178.4	142.7	118.9
177.8	512.8	341.9	256.4	204.9	170.9
203.2	739.5	493.3	369.7	295.4	246.7
254	133.8	891.8	668.9	534.2	445.9

Diameter of gutter 41.7 mm/m slope	Maximum rainfall	in millimeters per	hour
50.8	76.2	101.6	127	152.4
76.2	89.2	59.5	44.6	35.7	29.7
101.6	189.5	126.3	94.8	75.8	63.2
127	328.9	219.2	164.4	131.5	109.6
152.4	514.7	343.3	257.3	206.2	171.9
177.8	724.6	483.1	362.3	289.9	241.4
203.2	1040.5	693	520.2	416.2	346.5
254	1858	1238.4	929	743.2	618.7

Now, let’s look at the example given by the Standard Plumbing Code (Figs. 6.9 to 6.15). Some plumbing codes have recently joined forces to create a cohesive code. Most of this book is based on the International Plumbing Code, but there are others and there are combinations. Keep in mind that every code jurisdiction can create their own amendments to the code, so you must refer to your local, enforceable code to be sure that you are on track with local requirements.

STORM-WATER CALCULATIONS

The sizing example you have just seen is a good, step-by-step example of how to size a drainage system for storm water. You’ve seen actual code examples and rulings, but remember that these codes are subject to change and may not be the codes being used in your area. Consult your local plumbing code for current, applicable code requirements in your region.

SECONDARY (EMERGENCY) ROOF DRAINS Secondary Drainage Required

Secondary (emergency) roof drains or scuppers shall be provided where the roof perimeter construction extends above the roof in such a manner that water would be entrapped should the primary drains allow buildup for any reason.

Separate Systems Required

Secondary roof drain systems shall have piping and point of discharge separate from the primary system. Discharge shall be above grade in a location which would normally be observed by the building occupants or maintenance personnel.

Maximum Rainfall Rate for Secondary Drains

Secondary (emergency) roof drain systems or scuppers shall be sized based on the flow rate caused by the 100 year 15 minute precipitation as indicated in Fig. 8.12. The flow through the primary system shall not be considered when sizing the secondary roof drain system.

CONVERSION OF ROOF AREA

General

Where roof drainage is connected to a combined sewer, the drainage area may be converted to equivalent fixture unit loads.

Less Than 256 Fixture Units

When the total fixture unit load on the combined drain is less than 256 fixture units, the equivalent drainage area in horizontal projection shall be taken as 1000 sq ft (92.9 m2).

Greater Than 256 Fixture Units

When the total fixture unit load exceeds 256 fixture units, each additional fixture unit shall be considered the equivalent of 3.9 ft2 (0.3623 m2) of drainage area.

Rainfall Other Than 4 Inches (102 mm) Per Hour

If the rainfall to be provided for is more or less than 4 inches (102 mm) per hour, the 1,000 sq ft (92.9 m2) equivalent in 1110.2 and the 3.9 sq ft (0.3623 m2) in 1110.3 shall be adjusted by multiplying by 4 and dividing by the rainfall per hour to be provided for.

VALUES FOR CONTINUOUS FLOW

Where there is a continuous or semicontinuous discharge into the building storm drain or building storm sewer, as from a pump, ejector, air conditioning plant, or similar device, each gallon per minute of such discharge shall be computed as being equivalent to 24 sq ft (2.23 m2) of roof area, based upon a 4-inch (102 mm) rainfall.

FIGURE 6.10A ■ Rainwater code requirements. (Courtesy of Standard Plumbing Code)

BACKWATER VALVES

Fixture Branches

Backwater valves shall be installed in the branch of the building drain which receives only the discharge from fixtures located within such branch and shall be located below grade.

Material

Backwater valves shall have all bearing parts of corrosion resistant material. Backwater valves shall comply with ANSI/ASME A112.14.1 or CSA B181.1, CSAB181.2.

Seal

Backwater valves shall be so constructed as to insure a mechanical seal against backflow.

Diameter

Backwater valves, when fully opened, shall have a capacity not less than that of the pipes in which they are installed.

Location

Backwater valves shall be so installed to be accessible for service and repair. APPENDIX REFERENCES

Additional provisions for storm drainage are found in Appendix В-Roof Drain Sizing Method. These provisions are applicable only where specifically included in the adopting ordinance.

FIGURE 6.10B ■ Rainwater code requirements. (Courtesy of Standard Plumbing Code)

STORM-WATER CALCULATIONS

FIGURE 6.11 ■ Rainfall rates for primary roof drains (in/hr). (Courtesy of Standard Plumbing Code)

STORM-WATER CALCULATIONS FIGURE 6.12 ■ Rainfall rates for secondary roof drains (in/hr). (Courtesy of Standard Plumbing Code)

APPENDIX В

Welded Steel Box Girder Bridge

Posted by admin on 16/ 11/ 15

The steel box girder bridge is depicted in Fig. 4.10. The steel elements are fabricated and erected as “tubs,” and the composite concrete deck is placed in the field. This configuration has some advantages over plate girder construction. Visually, it is “cleaner,” and it does not provide surfaces for birds to perch. For high-visibility bridges, such as urban interchange bridges where motorists are constantly passing beneath the bridge, the enhanced appearance may be a deciding factor. Also, the cleaner surface areas tend to improve durability and reduce repainting costs. The bridge is torsionally stiff—especially

Welded Steel Box Girder Bridge

FIGURE 4.10 Cross-section of bridge with steel box girders.

beneficial for horizontally curved bridges. These advantages come at a price, however, because box girder bridges are generally more expensive than plate girder bridges. Sometimes the extra cost is knowingly borne for the aesthetic advantage.

Rafter Guidelines

Posted by admin on 16/ 11/ 15

There are calculators that are made specifically for assisting with construction math. These are very helpful in finding rafter lengths. Construction Master IV® is one available calculator, which we will refer to and use in this chapter to demonstrate the process of finding rafter® lengths. These calculators make it easy to do the complicated math, working in feet and inches. The sequence of buttons takes a little time to master, but once you are familiar with them, you will never go back to pencil and paper.

Learning by Example

The best way to learn cutting of rafters is to completely work through the actual process. The following example uses the diagonal percent method of finding rafter lengths. The example shows how to find the lengths of the parts of a relatively difficult roof. If you are able to work through this example and understand the processes, you should be able to figure out how to cut and stack rafters.

This example starts by organizing the whole process. Some of this information was presented earlier in the chapter, but it’s important to review for every job. We’ll start by outlining the important parts of cutting rafters.

Considerations for Cutting Rafters

When cutting rafters, you need to consider the following four factors:

1. Figuring rafter length

2. Figuring the Adjustment to rafter length at top and bottom

3. Finding the angle cuts at the top, bottom, and at the bird’s mouth

4. Finding the bird’s mouth height

Construction calculator designed to assist in construction math.

Figuring Rafter Length

Figuring Rafter Length Using Diagonal Percent was shown earlier in the chapter with the six ways to figure rafter lengths. (See "F.") When you use the diagonal percent, the most difficult part of figuring rafter length is finding the length of the run. The adjustments that need to be made at the top and bottom of the rafter should be added and subtracted from the run before the rafter length is calculated.

In finding the run, it is best to start with the full run distance from the outside of the bearing wall to the framing point of any connecting framing member. Use the framing point for consistency, and then make adjustments from there.

Figure the Adjustments to Rafter Length at Top and Bottom

Because there are so many different types of connections for rafters, it helps to establish certain standard ways to connect, and measure them in order to find the proper adjustments to length for the top and bottom. Following are some standard connections and their adjustments. They will not apply to every situation, but they will work for the most common roofs.

Adjustments for Common Rafters

1. Subtract half the thickness of the ridge board at the top.

2. At the bottom measure to the outside of the wall framing (not the sheathing).

1. Subtract half the 45° thickness of the ridge board. (See “Connection # 1 [close-up] illustration later in this chapter.)

2. At the bottom, measure to the outside corner of the two connecting walls.

Adjustments for Jack Rafters

1. Measure to the framing point where it meets the hip or valley it is connected to. (See “Adjusting the Top Length for Jack Rafters" illustration later in this chapter.)

2. Subtract half the 45° thickness of the valley rafter.

3. When the rafter rests on an exterior wall, measure to the outside of the wall framing.

Adjust Length for Top of Common Rafter

IV2" Ridge board ^ 12

22V2" 24

■ Span 14-0"- Adjustment:

Subtract V2 the thickness of the ridge board. This example = %"

This example:

Plumb cut height at bird’s mouth =

Run diagonal = 6ЧІ/4" x 1.118 =

Overhang diagonal = 22Уг" x 1.118 = 2′-1 J/ls"

Rafter length = Run diagonal + Overhang diagonal = 9′-10/іб"

1. Measure to the framing points where it meets the hip or valley it is connecting to. (See “Adjusting the Top Length for Jack Rafters" illustration later in this chapter.)

2. Subtract half the 45° thickness of the hip or valley rafter at each end.

Adjustments for Miscellaneous Connections Between Hips, Valleys, Ridges, and Rafters

1. Find the combination of cuts that provides the greatest number of standard cuts and still provides a sound structural connection.

2. Measure to the framing point for making adjustments.

3. Connection #2 is an example of a miscellaneous connection where a ridge board, a common rafter, a hip rafter and a valley rafter connect. (See “Connection #2" illustration later in chapter.)

Finding the Angle Cuts at the Top, Bottom, and at the Bird’s Mouth

It is easy to figure the angle cuts if you break them down into two separate angles. The first is the pitch angle, and the second is the connection angle.

The pitch angle is either a common or a hip/valley. If you use a speed square, you don’t even have to calculate it. If you are cutting a rafter that is not a hip or a valley, then use the common scale on a speed square for the pitch of your roof and draw your pitch angle line on the rafter. If you’re cutting a hip or valley rafter, then use the hip-val scale on the speed square. The pitch angle line will be your cut line for your saw cut.

The connection angle depends on a lot of factors, but 45° and 90° are the most commonly used angles. Basically, you will be setting the angle of your saw at the connection angle and cutting the cut line created by the pitch angle. For 90° corners on hips and valleys, the connection angle for jack rafters will be 45°. For standard, common rafters, the top connection angle is 90°.

Finding the Bird’s Mouth Height

The height of the bird’s mouth will affect the height of the roof and possibly the interior design of the ceiling. The most common detail for a bird’s mouth has the bird’s mouth cut starting at the inside corner of the wall.

On a hip and valley, the inside corner won’t align with the wall. Since the height of the hip and valley bird’s mouth must be the same as the common rafter bird’s mouth, you can simply measure the common rafter height and transfer it to the hip and valley bird’s mouth. The chart on page 103 shows some common bird’s mouth heights.

On hip rafters, you measure the height to the outside edge of the hip, whereas on valley rafters, it’s a little tricky. You need to measure to the center of the valley, which is slightly higher than the outside edge.

Toenailing

Posted by admin on 16/ 11/ 15

Carpenters need to know how to drive a nail at an angle. This technique is called toenailing and is often used to join pieces of wood that meet at a right angle.

When toenailing, you have to be careful not to split the wood, which is easy to do when you’re nailing so close to the end of a board. You can often avoid splitting the wood by dulling the point of the nail. Place the nail head on a hard surface and tap the point several times with your hammer. Instead of spreading the wood fibers and splitting the wood, the blunt point will simply break the wood grain as it penetrates.

To toenail two boards, hold the nail at a 60° angle and start it about 3A in. from the end of the board that’s perpendicular to the other (or you can start the nail straight in, then pull it up to the correct angle). Then drive it home into the adjoining piece of wood.

Toenailing

Bracing and splicing girders

Toenailing

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Rafter Guidelines

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