Innovations under the Han

The first imperial era was of great importance to the blossoming of China thanks to its cultural unity and construction of hydraulic infrastructure. Before moving on, we need to note the appearance of several other important innovations.

One innovation is the axial ship rudder (see Figure 8.10). We know that it appeared during this period from a terra-cotta scale model of a junk that dates from the 1st centu­ry AD and was discovered in a tomb at Canton.[421] At first, this was a movable rudder mounted on the stern of the hull. Later, it is attached to the sternpost of junks. The axial rudder is not adopted in the West until the 11th century.

A second innovation is the water wheel, appearing during the time of Wang Mang at the beginning of the 1st century AD. It is curious that the first literary references to the use of hydraulic energy in China are not about water mills, but about much more com­plex industrial applications. The first mention of a water wheel appears in 21 AD. This wheel is probably horizontal, and its axle shaft is fitted with cam lobes to drive an assem­bly of pestles.[422] The system is used to crush grain, and also to power forges. Ten years later (31 AD) a certain Du Shi, the son of Zhao Xincheng who built the dam that we described earlier, introduces the use of hydraulic energy to power piston bellows in the forges at the important metallurgical center Nanyang.[423]

While the axial rudder is clearly a Chinese invention, the hydraulic wheel is more likely an imported technique since there is evidence of its use somewhat earlier in Asia Minor at the beginning of the 1st century BC (see Chapter 5). The spread of this tech­nology into China is more or less contemporary with its appearance across the Roman Empire, albeit for different applications. However the exact origin of this invention remains obscure.

Another innovation that appeared under the “latter” Han appears rudimentary but is extremely effective for raising water. It is a device comprising a wooden chain fitted with rectangular paddles, like quoits, and powered by a sort of chain wheel (Figure 8.18). This square-pallet chain pump, the dragon backbone machine, is destined to spread throughout the lands of Chinese culture, and we return to this later on. It likely grew from the need for cities to lift water from cisterns or watercourses. We know from a treatise of Wang Ching in about 80 AD that in the capital Luoyang, men are employed “night and day” to lift water from cisterns to the street level – but he does not describe how it is lifted. A century later, in 186 AD, another treatise mentions the paddle pump very explicitly, again in the context of lifting water to the street level at Luoyang.

These lifting machines probably supplied water distribution networks of some sort. Conduits of stone or terra-cotta have been found dating from the Qin or Han periods.[424]

Bamboo tubes were probably used as well.

Another innovation that appeared in China in the 2nd century AD is the modern sail,[425] that is, a sail carried by a boom or yard that pivots around the mast. This type of sail rig can point into the wind, and it is not necessary to lower the sail when coming about, since the sail pivots on its own when the boat turns across the wind, or tacks. The Chinese sails were made of braided bamboo, stiffened with battens or yards so that they

Innovations under the Han

Figure 8.10 The rudder on Chinese boats (engraving of Chambers, 1757 – ancient archives of ENPC).

do not luff when brought close to the wind. It is not necessary to lower the sails when the boat is moored, and when the wind freshens, it is easy to reduce the sail area.

At the same time as the galley ship is being developed in the West, these Chinese sailing innovations support considerable coastal navigation along the shores and rivers of China, in particular on the Yangtze.

Under the Han, some canals are provided with gated openings. The Bian canal is the principle example; we saw earlier that such gates are mentioned as part of the recon­struction works of 70 AD. They are also mentioned in an older account, again from Jia Ran in 6 BC whose report proposes solutions to prevent flooding from the Yellow River: “We could construct a rock dike from Chhi-Khou toward the east and build many gates. [….]

I fear that this proposal will attract criticism saying that the river is too large to be controlled. However, we can evaluate our chances of success from the experience that we have on the Bian canal at Jung-Yang. At this location, the openings or gates were only made of wood, and set directly on the earth of the dike. Therefore, if we constructed these dikes out of rock, with good foundations, the safety of the works would be assured. [….] During the dry season, the lowest gates to the east should be opened to irrigate the countryside of Chichow, and during the flood season, the large gates of the west should be opened to route the river’s floodwaters far away.”[426]

Подпись:  Figure 8.11. A traditional fishing boat on lake Taihu, to the east of Shanghai (photo by the author)

The existence of gates on small irrigation canals stems from olden times that cannot be precisely pinned down. It is unlikely that they are in general use on large canals

throughout China until the 1st century BC, for Sima Qian does not mention anything like them in his observations. Recall that such gates existed in Egypt during the Ptolemite period, 3rd century BC, at the end of Necho’s channel – as well as in the Fayoum depres­sion (Chapter 5). The principle of a portable plank-dam was well known even earlier in Syria (see Chapter 2, the dams around Ugarit). In China, these single gates generally consist of several planks laid horizontally, one on top of the other, between guides set into each bank. On the larger applications, the planks are interlocked, and the assembly is operated using a system of pulleys and counterweights.[427]

On the navigable canals the gates are closed to maintain sufficient water depth when the discharge is low with respect to the slope of the canal. When the gates are opened,

boats moving downstream are carried by the wave that is created. Boats moving upstream, on the other hand, must be winched upstream of the gates using a capstan. After the gate is closed it takes some time before the water depth increases sufficiently for navigation to resume. This clever system constitutes the principle of the Chinese flush lock. As we see further on, this type of simple lock sees broad use on the Grand Canal.

Finally, even though this does not directly involve hydraulics, we must also note another Chinese innovation of this period: the humble but ergonomic wheelbarrow.

Primers and Paints*

Подпись: SURFACE PRIMER AND PAINT COMMENTS Drywall Unpainted Acrylic latex primer and paint Don't sand between coats Painted with oil-based semigloss or gloss Oil-based (alkyd) or latex To switch to latex: sand oil-based paint, vacuum, prime with acrylic latex primer Painted with latex Acrylic latex Sand lightly before first new coat; not needed thereafter Plaster Unpainted Acrylic latex primer and paint Plaster must be cured before painting; dilute primer coat Painted with oil-based semigloss or gloss Oil-based or latex To switch to latex: sand oil-based paint, vacuum, prime with acrylic latex primer Painted with latex Acrylic latex Lightly sand before painting Interior trim Doors, unpainted Oil-based primer and paint; semigloss finish Oil-based paint soaks into wood, dries harder, resists abrasion; sand between coats Unpainted Clear finishes, such as polyurethane and varnish Always seal bare wood or it will become grimy and dull Painted with oil-based semigloss or gloss Oil-based paint Sand between coats Painted with latex Acrylic latex Not as durable as oil-based paint Exterior Siding and trim, unpainted Acrylic latex primer and paint Latex stays flexible, allows some moisture migration Painted with oil-based semigloss or gloss Oil-based paint Unless you strip siding, stick with oil-based paint Painted with latex Acrylic latex * OiL-based here is synonymous with alkyd, now mentioned on most containers of paint and stain. Alkyds are synthetic resins that have largely replaced the traditional petroleum-oil base.

As you paint, be methodical so you won’t need to touch up missed areas. Paint top to bottom: Do ceilings, walls, trim and baseboards before doing doors and windows. Paint back to front: Many painters go to the deepest recess of a room— often, a closet—and work methodically toward a

Подпись:image909Подпись: When cutting corners or trim, slightly overlap the paint on the adjacent surface: 1/s in. to V4 in. Overlapping prevents unpainted spots, fills minor irregularities, and ultimately produces a cleaner line. It's also faster. Remember: You don't need to paint a perfectly straight cut-line till you apply the finish coat to the trim.Подпись: 1111Подпись: Use a hot-dog roller to fill those tight spaces over doors, around windows, inside cabinets, and the like.

door. Paint inside to out: If you start painting in the backs of built-ins and cabinets, your final brushstrokes on the outermost edges will be clean and crisp.

Once you’ve prepped the surfaces, masked off baseboards, and spread your drop cloths, it’s time to paint.

Painting the ceiling begins by using a brush to cut in a 2-in. to 3-in. border where the ceiling meets the walls and near all moldings. This cut-in border reaches where a roller can’t and thus allows you to roll out the rest of the ceiling with­out getting paint on the walls. Later, as you roll within h in. to 1 in. of the ceiling-wall intersec­tion, you’ll cover the brush marks, so the paint texture will look uniform. This operation goes much faster if one painter on a step bench cuts in, while the second painter rolls on paint, using an extension pole to reach the ceiling.

To avoid obvious lap marks, paint the ceiling in one session, working across the narrowest dimension of the room. Roll out paint in 3-ft. by 3-ft. sections—about one roller-load of paint. First roll the paint in a zigzag pattern, which distrib­utes most of the paint (fat paint) in three or fours strokes; then go back and roll the paint evenly. When the roller is almost unloaded, slightly over­lap adjacent areas already painted. Keep roller passes light, and don’t overwork an area. Once the paint is spread evenly and starting to dry, leave it alone so its nap marks can level out.

For a smooth finish, use a standard 9-in. roller cover with %-in. to И-in. nap. Thanks to the exten­sion pole, you can reach the ceiling easily, with­out needing to stand directly under the roller and its fine paint rain. To minimize mist and drips,
run the roller up and down the bucket ramp several times when loading. But don’t fret about small, stray spots on walls because you’ll cover them later when you roll the walls.

Painting the walls is nearly the same as painting ceilings— cutting in with a brush and rolling larger areas—except that you can load more paint on the roller. To reduce spatter, roll up on the first stroke; the excess will fall back to the roller. Continue rolling in a zigzag pattern to unload the roller before rolling out the paint. A 6-in. hot-dog roller can paint the areas over doors and windows that are too narrow for a standard 9-in. roller. Rolling is always faster than brushing because you don’t need to dip a roller in paint continually. If you’re careful around electrical outlets, you can also use a hot-dog roller there.

Подпись: Most amateurs fold sheets of sandpaper in half, then in quarters. But sheets will last longer if you fold them in thirds. Folding sandpaper in fourths places abrasive surfaces face to face, causing premature wear. 1111 Подпись: PROTIP Too often, amateurs dab paint on,which leaves crooked lines and uneven paint thickness. As you cut-in or paint trim, use long brush-strokes. Apply paint generously to the surface, and then smooth it out. For best brush control, hold the handle, not the ferrule, as if you were throwing a dart. llll image911Подпись:

After unloading most of the paint on the roller in a zigzig pattern, spread it out evenly, top to bottom.

With more paint on your roller, you can cover slightly larger expanses of wall, say, 3 ft. by 4 ft. If you start at the top of the wall and work down, you’ll roll over any drips from above. Cover brush marks by rolling within ’/2 in. to 1 in. of the ceiling; this is important when applying darker hues because rolled-on paint reflects light differently from brushed-on. Slightly overlap adjacent sec­tions. To avoid unloading excess paint along outside corners, lighten up as you roll.

Finally, sand lightly between coats when you apply oil-based paint, especially enamels on cabinets or trim. On walls, use 220-grit sandpaper or a dry sand­ing block. It’s not necessary to sand latex paint, unless you’ve waited several weeks between coats; until latex is 100% dry, new coats adhere easily.

Painting the interior trim

begins with the preparation tasks. Prepare the trim, window sashes, and doors by filling nail holes with nonshrinking wood filler, priming bare wood, caulk­ing gaps with acrylic latex caulk (letting it dry overnight), lightly sanding all trim with 180-grit sandpaper, and vacuuming dust and debris. Enamel paint—which dries to a hard, glossy finish—is best for trim, window sashes, and doors because it’s the most durable. By the way, there are both oil-based and latex enamels.

Painting straight edges requires a quality brush and a steady hand. If you can develop a steady hand, you won’t need to apply and remove masking tape, which takes a lot of time. In most cases, all you need is a 2/2-in. or 3-in. angled sash brush, unless your baseboards are exceptionally wide. Start with crown (ceiling) molding, pro­ceed to door and window trim, and finish with the baseboards. Always paint with the grain, cutting trim edges first, then filling in the field with steady back-and-forth strokes. To avoid lap marks, paint about 3 ft. of trim at a time, overlap­ping adjacent sections while they’re still wet. If the paint is drying too fast, add Flood’s Floetrol to latex paint or its Penetrol to oil-based paint.

Подпись:Подпись: 3. Pat the second accent color on. Then flip the sponge to its dry side and gently move the color around, spreading paint, not removing it; the wet side of this sponge would have streaked the paint. Stand back periodically to check whether the faux effect looks consistent from wall to wall.

Primers and Paints*
Подпись: FAUX
Primers and Paints*
Подпись: 1. After pouring a small amount of the first accent color into a shallow container, load your stippling brush lightly. Then quickly jab the bristles at the wall to create a stippled effect. Follow with a dry rag, lightly patting the just-applied paint to flatten the stipple points. Just flatten the points, don't remove the paint itself.

image913image914image915If trim edges are thinner than Yu in., they’ll be difficult to cut-in without spreading trim paint on the wall. In that case, overlap the wall paint onto the trim edge so that it covers the edge completely, producing a clean, straight line. In other words, the thin edge of the trim will be covered with wall paint, not enamel, but your eye won’t notice.

Windows sashes vary greatly in design. But as a general rule, paint them from the inside of the sash out. That is, if sashes are divided into multi­ple panes by muntins (narrow wood sections between panes of glass), paint the muntins first. Then paint along the insides of sash rails and stiles where they meet glass. Finally, paint the faces of sashes. To develop a rhythm, paint all the

Подпись: I Painting a Double-Hung Window (Interior View)Подпись:Подпись: 2. Reverse the position of the sashes and paint the rest of the upper sash.Подпись: Raise outer sash.Подпись: Lower inner sash.image916Подпись: 3. Once the paint is dry enough to handle, lower both sashes completely and paint the upper half of the jambs. When that's dry, raise both sashes, and paint the lower half, and then the window trim.vertical muntins—one side at a time—then the horizontal muntins. By painting similar windows elements at the same time, rather than jumping around, you’ll be less likely to miss elements and the work will go faster.

Don’t worry about cutting in clean edges at the glass. Instead, paint slightly onto the glass (Кб in.), even if unevenly, thus creating a tight seal. After the paint dries, use a razor to cut a clean line on the glazing.

image917

Raise inner sash.

Lower the outer sash and paint its lower half.

image918

Jambs

Lower and later raise both sashes to paint jambs and trim.

Open windows to paint their edges. When painting double-hung windows, follow the steps at left. If you are repainting the exterior of the house at the same time, go outside and paint the accessible parts of the window. Slide the window sashes back to their original position, and finish painting. To prevent binding, move the sashes as soon as the paint is dry.

Painting a door is easiest if you pull its hinge pins and lay it across a pair of sawhorses. (If that’s not possible, shim beneath the door so it can’t move.) For the best-looking results, remove all door hardware except hinge leaves, especially if you’re spray-painting. Cover the hinges with masking tape. If you prefer not to remove the old latch mechanism and escutcheons, carefully mask them too.

If you’re brush-painting a flush door (flat sur­face), divide it into several imaginary rectangles, each half the width of the door. Apply paint with the grain and overlap the edges of adjacent sections. Work from top to bottom. Painting panel doors is similar, but work from the inside out: Paint the insides of the panels first, next the rails (horizontal pieces) top to bottom, and finally the vertical stiles.

Painting cabinets is faster if you remove and spray-paint drawers and doors, and brush-paint cabinet frames. You’ll need a spray room isolated from the house (a clean garage is ideal); a drying rack for doors; and a sprayer, which you can rent.

Be sure to read the earlier sections on paint­ing safety and spray-painting, which emphasize ventilation, using electric heat in spray and dry­ing rooms, and wearing a respirator mask.

Start by washing doors and drawer fronts, especially those near the kitchen stove. If your cleaner isn’t cutting the grease, try TSP or denatured alcohol, wearing goggles and gloves. That done, examine the cabinet parts and their hardware, and plan to replace the doors or drawer fronts that are warped or not repairable, as well as hardware that’s broken or outdated. Before dis­assembling cabinet parts for spraying, assign each door and drawer a number. Write these numbers just inside the cabinet frame, where they won’t be covered by paint. Number the doors on bottom edges (least visible) or behind the hinges.

If you’re reusing the hinges, use a utility knife to score the hinge locations into each door. Note: Tape over door-hinge mortises if you’ll reuse the hinges. Otherwise, paint buildup in the mortise may misalign the hinges and thus the doors. Either cover the mortises with tape or leave the hinges on the doors and mask off the hinges.

Remove hardware before prepping the doors. If existing paint is flaking or the doors are dented, start with 100-grit sandpaper in a random-orbit

image919

To spray-paint a door, first place it across sawhorses at a comfortable working height. Mask hinges to keep paint off and ensure that the doors will hang correctly when reinstalled. Then move the sprayer smoothly and continuously, maintaining a constant distance from the surface. Overlap preceding passes by about a third. On each pass, begin spraying before the spray tip is over the door, and don’t release the trigger till the paint fan is past the far edge. Use your free hand, as shown, to keep the hose out of the way.

 

sander, wipe off dust with a damp rag, and then fill cracks and holes with nonshrinking wood filler. Repeat the sequence as needed, ending with a 220-grit sanding by hand. However, if the old paint is in good condition, a single pass with 220-grit paper and a damp rag is all you’ll need to prep before painting.

Подпись: When spray-painting only the face of a drawer, mask off the rest. For the most durable surface, apply a coat of primer-sealer, followed by three coats of enamel, which will hide well, even if you’re applying light paint over dark. Use acrylic-latex paint for the primer and finish coats, even if the cabinets are presently covered with oil-based enamel. Top – quality latex enamel is almost as tough as any oil – based enamel, it dries faster, and it’s much easier to clean up. To minimize runs, keep the doors horizontal during spraying and drying. Between coats, sand lightly with 320-grit garnet sand­paper. Painting drawer faces is essentially the same, except that you should mask off the drawer sides. Paint cabinet frames from the inside out, finishing with long, vertical strokes on the frame faces.

Подпись: Homemade Drying Rack This freestanding drying rack is constructed from 8-ft. lengths of ‘/2-in. galvanized-steel electrical conduit, 2x2 frames lag-screwed together, and two pieces of 3/4-in. plywood. The plywood base is roughly 30 in. by 30 in.; the ply-wood top can be smaller, say, 18 in. by 18 in. Drilling the holes slightly larger than the conduit diameter allows quick disassembly. To keep the conduit from getting dinged during transport, store it in 3-in. plastic DWV (drain, waste, and vent) pipe with capped ends; wrapping blue tape around the conduit prevents the metal's marring newly painted cabinet doors. To avoid tipping, load the rack from the bottom, unload it from the top, and balance the weight carefully side to side. image921Подпись: PROTiP To paint both sides of a door without waiting for the first painted side to dry, drive a pair of nails into the top and bottom of the door; then rest those nails on a pair of sawhorses. You and a helper can grab the nails and flip the door over. When both sides are dry, pull the nails; then fill and paint the holes. 1111 ^^PROTiP For some old-house purists, spray-painted finishes are too perfect. So, after spraying two finish coats, they use a 6-in. roller to apply a thinned (10 percent to 15 percent) final coat. They then tip off the surface with light strokes of a brush tip. Use a 3/8-in. mohair roller cover, which will not shed. Easy does it: Brush marks should be faint—barely visible, in fact. Подпись: 1111

Stripping and Refinishing Interior Trim

Natural wood can be handsome, but stripping layers of old paint or dulled finish is an enor­mously tedious, messy job. The following ques­tions and tests may give you easier options.

SIX QUESTIONS BEFORE STRIPPING

► What kind of wood? Builders often used plain or inferior-grade softwood for trim they intended to paint. Test-strip a small section to see if the wood is worth stripping. Common pine or spruce and badly gouged wood probably aren’t.

► How thick is the wood? If wood paneling is a Иб-in. veneer, it may be too thin to sand, let alone scrape and strip. © After turning off the electrical power, move panel battens (vertical pieces) or electrical outlet covers to see the edge of a panel.

► What kind of paint? Trim paint in houses built before I960 likely contains lead, which becomes hazardous if you sand it or heat-strip it. Yet it may be perfectly safe if it’s intact and well maintained. Analyze a paint sample, as explained on p. 443. Also, the more paint layers, the bigger the mess.

► Clear finishes that have become dull and grimy may just need a good washing. Using a damp rag, rub Murphy’s® Oil Soap onto a small section and wipe it dry quickly. If that clouds the surface, stop; but if it brightens the woodwork, keep going.

► If a clear finish remains dull after a test – wash or is worn looking, scuff-sanding and

a new application of the old finish may do the trick.

► If painted or clear finishes are cracking, peeling, or otherwise coming off, new coatings won’t stick. To test adherence, use a utility knife to lightly score a 1-in. by 1-in. area into nine smaller squares (like a tic-tac-toe array). Press a piece of duct tape onto the area and pull up sharply: If two or more little squares pull off, you should strip the paint or finish.

STRIPPING SAFELY

Before stripping woodwork, read "Painting Safely,” on p. 440, and "Lead-Paint Safety,” on p. 442. Many of the concerns when stripping are the same as those when painting. Most impor­tant, wear a respirator mask with replaceable filters. Also wear rubber gloves, goggles, and a long-sleeved shirt. Lay down plastic tarps (or lay­ers of newspaper) to protect floors and capture paint debris, mask off areas you’re not stripping, and ensure adequate ventilation. Even if a chemi­cal stripper is relatively odorless and claims to be eco-friendly—keep it off your skin and out of your lungs! Read instructions for all stripping chemicals before using them, and if you’re using a heat gun, have a fire extinguisher close by.

STRIPPING METHODS

Test-strip small sections of woodwork to see which method—or combination of methods— works best for you.

image922

Stains and clear finishes are thinner than paint and more inclined to run, so mask off adjacent areas before starting prep work.

Metal scrapers with straight edges work well on flat surfaces without too many layers of paint or clear finish. A scraper with changeable heads enables you to scrape varying contours. For best results, hold the scraper head roughly perpendi­cular to the surface and pull the tool toward you. Caution: Sharp scraper heads can easily gouge wood, especially softwoods like fir and pine, whose contours may obscured by thick paint.

Heat guns soften paint so you can scrape it off. Heat guns can remove many layers of paint, but stay alert when using them. Maintain a constant distance from the surface you’re stripping, and keep the gun moving so you don’t scorch one spot. Using a heat gun on shellac and varnish gets tricky because they have low kindling tem­peratures and tend to burn when heated; first, try stripping them with metal scrapers.

What’s That Finish?

To identify your woodwork’s finish, rub on a small amount of the test-solvents in this list, starting at the top of the list (the most benign) and working down till you’ve got your answer. When applying solvents, wear rubber gloves, open the windows, and wear a respirator mask.

► Oil. If a few drops of boiled linseed oil soak into the woodwork, you have an oil finish: tung oil, linseed, Watco® or the like. If the oil beads up on the surface, the woodwork has a hard finish, such as lacquer, varnish, or shellac. Keep investigating.

► Denatured alcohol. If the finish quickly gets gummy, congratulations! It’s shellac, which will readily accept a new coat of shellac after a modest sanding with an abrasive nylon pad or 220-grit sandpaper. Older woodwork with an orange tinge is often shellac-coated.

► Mineral spirits (paint thinner). This

will dissolve wax immediately. Dampen a rag and wipe once. If there’s a yellowish or light brown residue on the rag, it’s definitely wax.

If your woodwork finish has an unevenly shiny, runny appearance, suspect spray-on wax.

► Lacquer thinner. This solvent dissolves both varnish and shellac, so try denatured alco­hol first. If alcohol doesn’t dissolve the finish but lacquer thinner does, it’s varnish.

► Acetone. This one will dissolve varnish, too, in about 30 seconds. But if acetone doesn’t affect the finish, it’s probably polyurethane.

Never use a heat gun next to glass—for exam­ple, on window muntins—because you could crack the glass. Heat guns can also ignite dry materials within walls, so stop using guns well before the end of the workday so woodwork can cool. Before you leave for the day, sniff around for smoke or "hot smells.”

Подпись:Подпись: In this 1920s house, the homeowner wanted an older look for the cabinets. So after spraying three coats of oil-based enamel, the painters rehung the doors and rolled on a final coat . . . Подпись: . . . which they then lightly tipped off with a dry brush, intentionally leaving very faint brush marks. For chemical strippers, a rule of thumb is the stronger and smellier the chemical, the faster it

Подпись: COMMON CLEAR-FINISH PROBLEMS Подпись: Orange peel, often seen near kitchens, is caused by airborne cooking oils. Подпись: Weeping is wood sap excreted over decades. Подпись: Wax buildup is characterized by uneven, shiny sections where sprayed-on wax has run. will strip paint or finish. For example, methylene chloride will soften multiple layers in 10 minutes to 15 minutes; whereas “safe” DBE (dibasic ester) based strippers may need 24 hours. Given enough time to work, a stripper should soften all layers of paint or finish. Follow the stripping­time recommendations on the container label. By the way, semipaste strippers are best for vertical surfaces. Even when brushed on thickly, they won’t run.

Chemical strippers require patience and care. Use a rag to cover the cap before opening the container, so stripper won’t splash on you. Pour stripper slowly into a work pail, and close the container immediately so it won’t spill if the con­tainer is bumped or knocked over. As you apply stripper, brush away from yourself. To avoid tracking stripper throughout the site, replace plastic tarps as they become fouled with softened paint. Or lay down newspaper, which is cheap and easy to roll up before stuffing it into a garbage bag.

Once your tarps or newspaper are in place, brush on stripper liberally. A 18-in. to 14-in. coating of stripper should stay wet long enough to soften all the layers of paint or finish. To make sure that slower strippers stay moist, press a sheet of light­weight plastic (polyethylene) right onto the stripper-coated woodwork; the stripper won’t dis­solve the plastic. Periodically lift an edge of the plastic and try scraping off the paint. Be patient: Remove the plastic only when the softened paint scoops off easily. Till then, leave the plastic on.

Although renovators usually use a wide spack – ling knife or a putty knife to scoop off softened paint, a wooden spatula with a beveled edge is a near-perfect tool because it won’t gouge the chemically softened wood. Whatever tool you use, unload sludge from your scraper after each pass. Use a toothbrush, a nylon potato brush, or a handful of wood shavings to dislodge softened paint from detailed or hard-to-reach areas. Only occasional spots should need additional stripper.

When the woodwork is bare, scrub off the stripper residue with a solvent recommended by the manufacturer—typically, mineral spirits applied with a nylon abrasive pad, then blotted dry with paper towels. Follow that with a dilute solution (5 percent to 10 percent) of household cleaner in warm water and wipe that off with paper towels. Allow the wood to dry thorough­ly—at least a day or two—before filling holes or sanding. Note: Don’t use steel wool to scrub strip­per or remove paint. Otherwise, steel particles can stick in the wood and then rust, marring the new finish.

image928

This hand scraper comes with six interchangeable stainless-steel blades, which will fit most contours you’re likely to encounter.

REFINISHING WOODWORK

Once your stripped woodwork has dried, patch it with wood putty that dries to the same color as the unfinished wood. (Putty lightens as it dries.) Test a number of putty colors, allowing each to dry well before test-staining or finishing. When a patch is so hard that your thumbnail can’t gouge it, the putty’s dry enough to sand.

Sanding. If the woodwork is in good shape and doesn’t need filling, just scuff-sand it (sand it lightly) with 220- or 320-grit sandpaper before applying a clear finish. More likely, you’ll need to use several grades of sandpaper, starting with 80-grit or 100-grit to sand down tool marks or dings, moving on to 150-grit, and ending with 180-grit or 220-grit.

Sand sections completely with one grit before switching to another, even if you think an area is smooth enough. If you switch from 120-grit to 150-grit while sanding a baseboard, for example, it may have two different shades when you stain or finish it.

If there’s a lot of woodwork to sand, use a palm-size power sander (also called a block sander) for the first three sandings, and finish up by hand sanding with the wood grain, using 180-grit or 220-grit garnet paper. Wrap sand­paper around a standard blackboard eraser or a scrap of 2×4 to hand-sand flat areas; sandpaper wrapped around a dowel works well on concave areas. After sanding, wipe or vacuum the surfaces to remove the dust.

Install attic stairs

Some people like to install a folding staircase to give them access to attic space. A factory – made folding staircase doesn’t meet the code requirements for a regular stairway, so it’s not designed for everyday use. But if it is installed properly and used carefully, a folding staircase works quite well.

Most folding staircases consist of three lad­der sections that are hinged together and attached to a ceiling-mounted trapdoor. The door is hinged and held flush to the ceiling with springs. You pull on a cord to open the door and pull down the stairs. As the door swings down, you can unfold the two bottom sections of the staircase (see the top photo at left). The entire unit fits into a rough-framed attic-access hole between ceiling joists. The opening is typically 22/ in. wide by 54 in. long. Simply follow the installation instruc­tions provided by the manufacturer.

The stair unit comes out of the box com­pletely assembled. When attaching it to the joist chords and header, use the screws that come in the package—not drywall screws. Drywall screws are relatively brittle, do not possess much shear strength, and can break under a heavy load. To support the unit dur­ing installation, screw temporary ledgers (sup­ports) to the ceiling joists that surround the opening. The ledgers should project about 1 in. into the rough opening. The ledgers hold the stairs while you secure it in place.

The unit is installed much like a prehung door. You need to shim between the sides of the stair jambs and the supporting joists before driving the screws through predrilled holes. Once a few screws are in place, open and shut the door now and then to ensure that it opens easily and that the reveal, or space, between the door and the jambs is even all the way around.

Install attic stairsПодпись: NO HAMMER NECESSARY. A pneumatic nailer drives and sets a nail with one lick and seldom splits the wood. [Photo by Charles Miller, courtesy Fine Homebuilding magazine, * The Taunton Press, Inc.JThe bottom section of the stairway must be cut to length, with the ends of the legs (or stringers) cut at the correct angle so they rest solidly on the floor. To find the angle, swing the staircase down and unfold all but the last section. Extend a 1×4 board alongside an upper-section stair stringer so that the 1×4 reaches the floor. Place another board on the floor and against the 1×4, then mark the cutoff angle on the 1×4. Once you cut that angle on the 1×4, transfer it to measured cutoff lines on both bottom-section stringers.

SETTING A PREHUNG DOOR

Подпись: Nails Maintain a Ve-in. margin through between the jamb and Подпись: Take your time setting a prehung door. Make sure it opens and doses with ease. Shim and nail the jamb to the trimmers to hold it securely in place.SETTING A PREHUNG DOORПодпись: MAKE A BLOCK FOR THE BRACKET. Set the bracket that supports the bottom pivot of a bifold door on a small block. This block will later be covered with carpet. [Photo by Charles Miller, courtesy Fine Homebuilding magazine, ф The Taunton Press, Inc.]

the hinge and jamb and into the trimmer.

This step helps anchor the hinges and hinge – side jamb to the wall framing.

Throughout the process, continually check the door to see that it opens and closes with ease and that the jamb sides cross-sight, as described in the sidebar on p. 245. If a prob­lem develops, its best to find out along the way, rather than after the last nail has been driven home. If you’re driving nails by hand, use a nail set to set them below the surface of the wood so they can be hidden with putty.

Install bifold and bypass doors

Bifold doors work well in small areas, such as closets and laundries. They are supported by top and bottom pivots or guided by an over­head track. I find bifold and bypass doors easy to install, but the less expensive versions are not very durable. Many of the cheaper models have fittings that just can’t take serious use. Good hardware costs more up front but may save you from having to replace the entire unit prematurely.

Step-by-step installation instructions come in every bifold and bypass door package. Once the trimmers and header have been wrapped in drywall, the opening for a bifold should be the size of the doors. A 3/0 bifold door is installed in a 36-in.-wide opening. The open­ing for bypass doors should be 1 in. less than the size of the doors. For example, a 5/0 bypass door needs a 59-in.-wide opening.

If the floor will be carpeted, nail a plywood block (usually about / in. or % in. thick) under the brackets that support the bottom pivot of bifold doors (see the photo at right). If you are working on a slab, drill holes in the con­crete and set sleeves in the holes. Then glue the block in place and screw it into the holes. The carpet will cover the block. A similar block needs to be placed in the center of bypass doors to hold the bottom door guide.

SETTING A PREHUNG DOORПодпись: A DROP-DOWN STAIRCASE PROVIDES EASY ACCESS. Installing a factory-made folding staircase lets you gain convenient access to attic space. [Photo by Jefferson Kolle, courtesy Fine Homebuilding magazine, s The Taunton Press, Inc.]SETTING A PREHUNG DOORПодпись:

WOOD-SHINGLE VALLEY & HIP

DIRECTION OF

 

extend FIELD

 

WOOD-SHINGLE VALLEY & HIP

WOOD-SHINGLE RIDGE

Wood shakes are popular for their rustic look and their durability. They are made from the same materials as wood shingles, but they are split to achieve a taper instead of being sawn. Shakes may have split faces and sawn backs or be taper-split with both sides having a split surface. In either case, the split side is exposed to the weather because it has small smooth grooves parallel to the grain that channel rainwater down the surface of the shake. Because the weather side of the shake is split, not sawn, and because they are consider­ably thicker, shakes will last a great deal longer than wood shingles made of the same material.

Standard shakes are 18 in. or 24 in. long and come in heavy or medium thickness. Wood shakes may be applied over open sheathing (see 166) or solid sheathing (see 163). The courses of shakes are usu­ally alternated with an interlayment of 30-lb. felt that retards the penetration of moisture through the relatively large gaps between shakes. Solid sheathing and cold-climate eave flashing (see 169B) are recom­mended in areas that have wind-driven snow.

SPACED ROOF
SHEATHiNG AT
SPACiNG EQUAL
TO COURSE
SPACiNG
OF SHAKES

SEE 166

 

INTERLAYMENT OF 18-IN. wIDE 30-lb. felt

 

OFFSET SPACE

between

SHAKES 11/2 IN.

 

2 NAILS PER SHAKE AT EDGE & ABOUT 2 IN.

 

INTERLAYMENT SPACING EQUALS COURSE SPACING.

 

18-IN. INTERLAYMENT BETWEEN LAYERS OF DOUBLE FIRST COURSE

 

18-IN. INTERLAYMENT UNDER DOUBLE FIRST COURSE

 

DOUBLE FIRST COURSE OVERHANGS EAVE ABOUT 2 IN.

3/4 IN. WITH GUTTER).

 

FOR SHAKE VALLEY & HIP (RIDGE) DETAIL, SEE 187A.

 

COURSE SPACING IS 71/2 IN. TO 10 IN., DEPENDING ON ROOF PITCH, SHAKE SIZE & GRADE.

 

RAKE FLASHING SEE 169C

 

(g) WOOD-SHAKE ROOFING

 

WOOD-SHINGLE VALLEY & HIP

30-LB. FELT INTERLAYMENT LAPS VALLEY FLASHiNG.

Подпись:Подпись: ALLow 3 iN. CLEARANCE TO CENTERLINE OF VALLEY. Подпись: 30-LB. FELT UNDER HIP OR RIDGE SHAKESПодпись:Подпись:Подпись: DOUBLE FIRST COURSE WITH ALTERNATE LApS. Подпись:WOOD-SHINGLE VALLEY & HIPnote

wood-shake ridge is similar to hip.

Road Runoff Collection and Treatment

Where there are environmentally sensitive areas or high traffic flows, increasing the risks of accidents and generating contamination from wear, water flowing over the surface of the road and the embankment should be collected before it can soak into the ground in an uncontrolled manner. Water seeping through the earthworks and collected by a drainage layer has to be led, by virtue of a fall in the drainage layer and by shaping it, to collection points. At the collection point the water quality can be monitored and, according to the quality measured, it can be fed to a soakaway (Section 13.4.7) or piped away for treatment.

Water that arrives at an outlet from a drainage system may need treatment to bring the water quality to an acceptable level. In extreme cases, conventional waste-water treatment systems can be installed, but such a level of treatment is seldom required, except where water has passed through some contaminated soil body. If the water could, following a traffic accident or similar, contain spillages of fuel or cargo from
traffic, then it will be necessary to install a oil/fuel separator. If these are installed then it will usually be sensible to provide a retention pond on the upstream side of the separator. This lagoon can act as a location to temporarily store the spilled fluid from which it can be extracted and taken away for off-site handling. The aim will be to give the road operator or environmental manager sufficient time to respond to the spill before the fluid is allowed to enter a surface water body or allowed to soak down to the groundwater. Storage lagoons also provide a zone in which solids can sediment from water and provide a means of attenuating the peaks of hydrographs.

Man-made wetlands and reed beds can also be provided as water purification areas (see Chapter 12, Section 12.3.1). They are particularly suited to groundwater outlets as the water arrival will be more consistent, at a low flow volume rate, than for surface water runoff and there will be much less need to provide storage for excess water arriving after a rain storm. Reed growth is much more suited to this consistent supply of water, while the area to be occupied by the water purifica­tion planting can remain relatively small. They often have the additional advantage of providing an enhancement to the pre-existing environment. Naturally occurring wetlands are under serious threat in most countries and they should not be used for this purpose.

The WATMOVE questionnaire sent to European road authorities (see www. watmove. org) revealed that settlement of solids and oil separation are the most common treatment methods used in practice, see Fig. 13.10.

Fig. 13.10 An overview of treatment methods used in Europe. The number is the percentage of countries in the survey using the treatment

Raising Heavy Timbers

Traditional timber framers will make all their bents ahead of time, and have them stacked in the proper order, waiting for the big day when plenty of help is gathered together for the raising. Lots of bodies wielding poles, as seen in Fig. 2.17, lift the bent to vertical. The poles can also act as temporary stops to aid during the lifting process. Someone — usually the boss — checks the bent for plumb, as diagonal bracing is fastened.

Oftentimes, professional timber framing contractors hire a crane for the big day.

My experience over thirty years has been to raise posts individually, brace them with temporary diagonal supports, and then to raise the girts or girders one at a time. Usually, this involves just two to four people, as at the Earthwood addition, but, in the case of a 30-foot ten – by-ten at Log End Cave, eight people and a pick-up truck were involved in the installation.

Mark Powers, now building a Log End Cave type of home with very heavy rafters, and working mostly alone, says: "With some creative engineering, I’ve been able to raise all of my girders and rafters with my trusty Kubota 45-horsepower tractor with its quick-attach forks and bucket. I can’t imagine building the house without it."

At Earthwood, I had fun raising a fairly green 15-foot ten-by-twelve oak girder — probably over 700 pounds (318 kilos) in weight — to the top of the posts, aided by just one other helper. We accomplished the feat by raising an end of the timber with a lever, and slipping a concrete block under it, about 40 percent of the way along its length. Now lifting the other end was easy, as the overhanging 40 percent of the beam’s weight cancelled out another 40 percent of the weight at the lifting end. Again, we made a slightly higher block stack 40 percent of the way in from the new lifting end. We alternated our lifts back and forth, end to end, always adding a block or two to the low stack. After a couple of lifts, we rebuilt the block stack with criss-crossed block construction, for greater safety and stability. In short order, we had the beam up to height, and then, one end at a time, transferred its load onto the braced posts.

to structural — problem, and it could easily have been avoided. But as I have said before, heavy timber framing is forgiving, particularly if you are willing to forgive yourself once in a while.

Cold Climate Effects

It is a design objective that snowmelt and rainfall should have fast access to the side of the road and the drainage system. This avoids surface ice formation and skidding, but also protects the structure so that as little water as possible filters through to the pavement. Edges, kerbs, channels and runoff barriers must be kept clear by routine maintenance. Sufficient snow storage (and snowmelt) capacity on the road side must be included in the design. Dry structures and the road bed should be effected less by frost.

During spring-thaw there is considerable increase in the moisture of many un­bound materials. The magnitude of the spring-thaw weakening (on bearing capacity and slope stability) depends, very much, on the functioning of the drainage system.

Due to snow cover on the road side, frost depth is typically deepest in the middle of the road and this will cause uneven frost heave across the section of road. The heave depends on how long the freezing front remains in the frost susceptible soil, the soil characteristics and also how much water there is (see Chapter 4, Section 4.6). If the frost heave differential is big enough, it can cause surface roughness, cracks, breakage of the surfacing and lifting stones (causing first roughness and later on surface cracking).

The permeability of most soils decreases when frozen. In springtime the frost can form an almost impermeable water barrier in the soil below the road since thawing will be fastest from the top and in the middle of the road. In that case the melted water will flow in a longitudinal direction until it can find an exit route, at which point it will flow to the road side or into the subsoil causing localised seepage and/or erosion problems.

Low permeability side-slopes decrease the infiltration of rainfall, but they can also act as flow barriers for the seepage of water out of the pavement structure and thus increase frost damage as well as decrease the strength of the structure. In that case openings with gravel filling at certain intervals and on low-lying locations can help the situation as in Fig. 13.9. Another option is a drain. A drain is the only option if the road structure is deeper than the open ditch at the side of the road.

Fig. 13.9 Outlet with gravel filling on a low permeability slope

If there is no outlet ditch or drain available, and the amount of water is small, the water may be soaked into the soil. A transition wedge of coarse material and non water susceptible structure can be used to avoid frost damages at a low lying location where water is periodically accumulated.

In cold climates, where frost heave in winter is a problem, an open-graded layer can be constructed at the bottom of the pavement to prevent water being pulled from the subgrade due to a freezing front in the pavement. This will lower frost heave in the road construction by decreasing the water content compared to pavements with­out a capillary break. However, frost-susceptible layers will always heave to some degree if there are freezing conditions. For example, Hermansson (2004) reports a field study where an extremely well drained soil heaved 80 mm during a period of two months. The open-graded layer will not affect frost heave in a susceptible sub­grade if the freezing front gets that low in winter, but it will significantly reduce the effect on the highway surface by allowing the road to bridge differential subgrade heaves.

More information on drainage of low volume roads in cold climates is given in a report by Berntsen & Saarenketo (2005).

SMA in an Intermediate Course

In some countries, SMA mixes have been applied in lower layers of the pavement structure. They are usually coarse-graded SMA mixes from 0/16 to 0/22 mm. Such solutions have been tested in the United States and recently in Germany, where they are called Splittmastixbinder (SMB) (Gartner et al., 2009; Schunemann, 2006). Because of the high binder contents, commonly a polymer modified binder with a stabilizer as well, the fatigue properties of the pavement are definitely better than those of conventional asphalt concrete. The application of a strong aggregate skel­eton increases the resistance to rutting.

In many cases, SMB 0/16 with a hard modified binder may be better than a conventional asphalt concrete layer. Experimental roadway sections in Bavaria (Germany) on the highway A73 are good examples of such an application (Gartner et al., 2009). The SMB mix has been designed with target air voids in Marshall specimens between 3.5 and 4.0% (v/v) and a minimum binder content of 5.0%. A hard modified binder (pen@25°C = 10/40, SP > 65°C) has been used. Figure 13.4

Подпись:Подпись: ofoO CO CN ^ in Ю CO V) г-н CN r-H ^ 40 CN CO Подпись:image1590

10

20

Подпись: a a Подпись: .c 5 CD 30

40

50

60

70

80

90

100

FIGURE 13.4 Grading curves (limits) of the SMB mix used on Highway A73 in Germany. (Data from Gartner, K., Graf, K., and Schunemann M., Asphaltbinderschichten nach den Splittmastixprinzip. Strasse und Autobahn, July 2009 With permission.)

shows the grading curves of the designed SMB mix. The thickness of the com­pacted layer has been defined as 7.5 cm, the required compaction factor greater than or equal to 98%, and the content of air voids in the finished course from 2.0 to 6.0% (v/v).

The test results on SMB mixes with hard grade polymer modified binder have confirmed that an intermediate course of this type can be a better solution than the conventional asphalt concrete; with a similar resistance to rutting, the fatigue life of SMB is remarkably better (Schunemann M., 2006).

Suitable Soils

Most research to date has been done in homogeneous soils. However, there is no rea­son why the concept cannot be applied to heterogeneous soil masses if proper consid­eration of soil properties is made and rationally applied to the selection of nail length and spacing.

To be economical, soil nailed walls should be constructed in ground that can stand unsupported on a vertical or steeply sloped cut of 3 to 6 ft (1 to 2 m) for one to two days, and can maintain an open drill hole for a few hours. Soils considered favorable to soil nailing are as follows:

1. Naturally cohesive materials (silts and low-plasticity clays that are not prone to creep)

2. Naturally cemented sands and gravels

3. Weathered rock

4. Fine to medium, homogeneous sand with capillary cohesion of 60 to 100 lb/ft2 (2.9 to 4.8 kPa) associated with a water content of at least 5 to 6 percent

According to FHWA Report RD-89-108, soil nailing is generally not considered cost – effective or applicable in the following soils:

1. Loose granular soils with field standard penetration N values lower than about 10 or relative densities of less than 30 percent

2. Granular cohesionless soils of uniform size (poorly graded) with uniformity coeffi­cient (D60/D10) less than 2, unless found to be very dense; nailing of these soils may be impractical because of the necessity of stabilizing the cut face (by grouting or another permanent technique) prior to excavation

3. Soft cohesive soils with undrained shear strengths of less than 500 lb/ft2 (24 kPa), because of the inability to develop adequate pullout resistance

4. Highly plastic clays (LL > 50 and PI > 20 percent), because of their potential for excessive creep deformation

5. Expansive (swelling) and highly frost-susceptible soils

Soil nailing is also not recommended for the following conditions:

1. In ground with water pressure present at the face

2. Below the groundwater table, unless the slope can be effectively dewatered prior to excavation

3. Loose fill, granular soil with no apparent cohesion