Chapter 7 Wooden structures.
Whether your structure is a multilevel deck or a simple trellis, the presence of a structure adds warmth, interest, and, in many designs, fulfills the important design principle of scale. Unlike paving and ground-level hardscape improvements, structures instantly change the dynamics of the design by introducing three-dimensional elements. Regardless of the function, adding a crafted wooden element brings another dimension to the landscape.
Several types of wooden structures have proven to be valuable additions to the landscape. Decks are surfaced platforms that serve several functions, including entry, grade transition, and entertainment. Enclosed structures such as gazebos serve as climate-controlled outdoor rooms. Arbors, or roofed structures with open sidewalls, provide both enclosure and openness (Figure 7-1). Simpler structures, such as trellises, can be built to support vines or to create shade for outdoor living areas.
The construction of wooden structures for the landscape is based on a simple concept: the fabrication of a floor, walls, roof, or any combination of these elements customized to meet your special needs. Design a unique collaboration of components, engineer them according to structural standards, and you have a structure you can enjoy for many years.
[FIGURE 7-1 OMITTED]
The construction and installation of many of the wooden elements designed to be used in a landscape setting require special skills, tools, designs and a high level of craftsmanship. Some of these elements also face the risk of collapse if the structural elements are not sized properly. Because of this, the construction of any structure intended to support humans should be contracted to a licensed professional for installation. Structures not intended for occupancy, particularly arbors and trellises, are projects most likely to be safely and successfully completed by the homeowner.
PLANNING THE WORK
You should considers several issues regarding materials when preparing for a carpentry project. The types of wood, fasteners, and finishes need planning and research before you ever pick up a tool. Information regarding the choices of exterior woods and wood-fabrication products is described in the sections following.
Woods and Materials for Exterior Use
Selecting the proper wood for your project requires consideration of several characteristics of wood and how the material is to be used. The primary choices for wood products used in exterior carpentry include naturally decay-resistant and treated woods milled into boards and dimensioned lumber.
Although treated softwoods remain the standard for structural (support) components, the landscape market also has a large number of alternatives to harvested woods. Composite and recycled materials are becoming increasingly popular alternatives to woods, for surface trim and finishing. To speed the construction of landscape structures, many components can be purchased prefabricated. Available in a variety of natural and artificial materials, the homeowner can find lattice, rail posts, and many other commonly used parts cut and ready for installation. The following sections describe some woods and materials that are commonly used for exterior carpentry.
Western Red Cedar
Cedar heartwood is a soft, naturally decay-resistant lumber that makes excellent surfacing and trim material. Because of its relatively high cost, cedar is usually not cut in structural dimensions (2 x 8's, 2 x 10's, etc. but is available as a surface and trim lumber. Cedar is soft and can be stained if desired or left to weather out to a mottled gray. Rough-sawn cedar boards are often used as trim for exterior work.
Redwood heartwood is a soft, naturally decay-resistant lumber that is excellent for decking and trim material. Heart redwood can also be used for structural members in most exterior applications. Redwood is soft and without finishing will weather to a warm dark gray.
Treated woods include a variety of pines, firs, and spruces that are treated by one of several methods to resist decay and insects. These woods have the strength to be used as structural support components for landscape carpentry but after being treated are not the best or safest choice for surface treatments. See the Cautions regarding wood treatments in the Decay Resistance section on page 166.
Wood composites and recycled materials
Wood-substitute components are available that provide a reliable surface, workability, and some degree of environmental consciousness. These surfaces are typically plastics or a blend of wood fibers and plastic, molded into the shapes and dimensions of deck surfacing. Most of theses composite materials are limited to surface treatments and are typically not strong enough for structural components. Sort through the variety of choices available at a local lumberyard, and pick one that offers strength, a fade-resistant color, and ease of workability.
Table 7-1 summarizes the characteristics of hardness, strength (ability to resist breaking when subjected to a load, decay resistance, and common uses for several exterior woods.
Woods such as cedar and redwood are naturally resistant to decay, and as long as the appropriate portion of the tree is used, there is no need to further treat these lumbers. In redwood, the heartwood portion is used for exterior construction. Most other woods available to the homeowner, including pine, fir, and spruce, are susceptible to decay and insect damage if not treated. Treatment methods for woods include the chemicals pentachloraphenol (also termed Penta), [ACQ.sup.R] (alkaline copper and quaternary, arsenicals (derived from different copper and zinc compounds, and creosote.
When improperly used, each of these chemicals has the potential to be toxic. Arsenicals are scheduled for discontinued use and creosote is not appropriate in situations in which it comes into contact with humans and plants consumed by humans. It is recommended that structures that bring humans, especially children, into contact with treated lumber be avoided. In these situations, use alternative decay-resistant materials.
These treatments are generally applied to lumber under pressure to force the preservative deeper into the wood. Look for treated woods labeled "Ground Contact" to ensure satisfactory performance in exterior structural projects. When treated wood is cut for use in a project, retreatment of the cut ends is necessary. Selection of a paintable or dippable treatment method will be the most efficient method for retreating. After cutting, dip or paint the preservative on the exposed surfaces and let them dry before placing them in contact with the ground.
* Avoid prolonged skin contact with treated lumbers. Working with treated lumbers requires wearing gloves and long-sleeved shirts to prevent exposing your skin to the chemicals used in the treatment.
* Wear a dust mask when cutting treated lumbers.
* Wash your hands thoroughly after contact with treated lumbers, wash the clothes worn when handling treated lumbers separately form other clothes, to prevent contamination.
* Do not let treated lumbers come in contact with food.
* Treated lumber should not be burned and must be disposed of in the manner prescribed by the manufacturer.
Most structural-dimensioned treated woods (2 x 8's, 2 x 10's, 4 x 4's, and larger) are durable and strong enough to use for posts, beams, joists, and surfaces that must support weight. Smaller-dimensioned lumber (2 x 4's, 2 x 6's) milled from woods such as redwood and cedar and composite materials are best suited for the trim and surfacing elements of the project, where the weight they carry is limited. If you are unsure of the ability of your design to support the weight that will be placed upon it, consult an engineer for advice.
Wood Color and Exterior Finishes
A key esthetic characteristic of any wood product is color. Generally, color can be described in two ways: as the initial color of the lumber and as the ultimate weathered color. Exterior woods have distinctive initial colors, and most will weather to a shade of gray if left unfinished. Cedar is initially a light tan and redwood a reddish brown. The consistency of the final color will depend on whether the surface is exposed to moisture, such as rain, snow, or irrigation, and whether it is under the cover of a roof. The more protection provided, the more consistent the final gray color will be.
Most treated woods begin with either a light green or brown cast. Because the structural lumber is not visible when in its final position, the color of treated lumber is not an issue for these pieces; however, if placed in a finish position (that is, where it will be visible when the project is complete, the coloring could be considered unattractive. If you choose to use a treated wood for a finish element, you will have to accept the colored cast left by many of the treatment methods. This discoloration can remain present for several years, but eventually the color will weather. Finishing with stain is an alternative in some cases, but many of the treatments prevent finishes from binding evenly with the wood.
Wood used in exterior conditions will face a variety of weathering conditions that will age the materials, change its color, and possibly begin the process of decay. You should decide during the planning phase of the project whether the wood selected for construction will be treated to deter the effects of weathering or allowed to age naturally. The primary reason to finish-treat such woods is to maintain the new look of the lumber or change the wood's natural color. Once finish-treating is selected for exterior woods it should continue throughout the life of the project.
To preserve the natural look of your wood, a water repellent with an ultraviolet light inhibitor must be applied to slow the weathering process. To change the natural color of the wood, a surface must be stained or painted. Two different types of stains commonly used with exterior applications include opaque stains, which provide a solid color coating over the wood, and transparent stains, which color the surface but allow the grain of the underlying wood to show through.
Cost and Availability
Selection of your wood products will often be dictated by which materials are available at a reasonable cost. Factors such as markets, transportation costs, and production schedules will all influence the price and may necessitate using whatever acceptable material is available. The factors of cost and availability are typically interrelated. The more available a product, the lower the cost. Products that are in short supply are more expensive.
Many of the woods that are treated, such as southern yellow pine and fir, are harvested from large stands and are typically available in greater quantities than woods such as redwood and cedar. Dwindling supplies of redwood have also introduced the ecological issue into material selection, causing some to select alternative choices.
The quality of the products you use will have a direct relationship to your project's appearance and stability. Avoiding wood that is warped, split, cracked, or has large knots will also improve the structural integrity of a project. Some defects, such as cupping, can be overcome by reorienting the lumber if the defect is not severe. Others will require trimming the defective portion from the lumber to make it usable. A serious defect would be cause for rejection of a piece of lumber (Figure 7-2).
[FIGURE 7-2 OMITTED]
Many people are confused by the sizes of lumber. When a 2 x 4 is first cut, the dimensions are actually 2" thick by 4" wide. The 2 x 4 dimension is the nominal dimension and is used when the product is sold. However, after drying and planing, boards are slightly smaller in their actual thickness and width than the nominal dimension. Using the nominal dimensions rather than the actual dimensions when measuring and cutting will result in errors. To avoid this problem, memorize and use the dimensions listed in Table 7.2. Length is not affected by this issue, but you should verify the length of a piece of lumber by measuring it before installation, to avoid problems.
Fasteners and connectors
Connectors, fasteners, and related hardware for exterior projects should be made of materials that resist rust naturally or are treated to resist rust. Galvanized materials are made of steel and then dipped in a zinc coating to reduce the chance of rusting when exposed to moisture. Galvanized materials are suitable for use with any type of treated lumber, but may stain wood if the galvanized coating is damaged. Polymer-coated fasteners are made of steel that has then been coated with a thin plastic like coating to resist rust. Polymer-coated fasteners resist rust and are easy to install because of their slippery coating. Though expensive, stainless steel connectors will provide a stain-free finish when used in contact with cedar or redwood. Your selection of fasteners will depend on how and where you expect your project to be used.
Several types of fasteners could be used in your landscape-construction projects. Among the choices are nails, wood screws, lag screws, carriage bolts, an array of premanufactured fasteners, and specialty connectors (Figure 7-3).
* Nails. Nails are pieces of hardened wire of varying diameters that are cut to length and flattened on one end (called the head) to make it easier to drive them into the wood.
* Wood Screws. Screws are similar in length to nails, but the shanks are tapered and threaded at one end so that they can be twisted into the materials to form a stronger hold. Screws can be driven with hand or power screwdrivers using slotted-, Phillips-, or square-headed drives. Screws are best installed by drilling pilot holes, holes drilled into the wood where the screw is to be installed. Pilot holes should be the same diameter as the shank of the screw and bored into the wood to a depth equal to at least half the length of the screw. Pilot holes will make installation easier and reduce the possibility of splitting the lumber.
* Lag Screws. The lag screw is a large-diameter long screw used for anchoring structural members. Lag screws require pilot holes that are the same diameter as the shank of the screw and drilled to a depth of at least two-thirds the length of the screw.
* Carriage Bolts. Carriage bolts are large-diameter bolts with rounded heads and square shoulders and are used for connecting structural pieces. Carriage bolts require a nut and washer at the end opposite the head to complete the connection. Carriage bolts also require that a pilot hole the same diameter as the bolt be drilled through all pieces of lumber being connected.
[FIGURE 7-3 OMITTED]
To improve and speed up the connection of building materials, a wide selection of specialized connecting and support hardware is available. Saddle connectors are available for joining 4 x 4 lumber. Straps, T's, angle braces, and post caps can all be used to make connections that are difficult to nail, screw, or bolt (Figure 7-4). Specialized hardware should be galvanized if it is for exterior use.
Supporting Wooden Structures
Your landscape structure will require some form of support to prevent the wind from lifting or blowing the structure over and, in areas in which the ground freezes, anchoring that provides adequate protection from frost heaving. You can do this by supporting your structure on existing slabs, footings or foundations, or posts buried in the ground. More complex methods of support, including anchoring your project to an existing structure, can be accomplished with the aid of a contractor.
Attachment to an Existing Slab or Footing
Connecting your structure to an existing slab will require either drilling and setting an expansion anchor bolt and galvanized-post anchor or making a connection using an angle brace. In cases in which wind may lift the structure, consider using both techniques. Setting an anchor bolt requires marking the center line location of each post, and then using a masonry bit to drill a hole the same width and depth as the expansion bolt. Drive the anchor bolt into the hole. Tighten the nut with a wrench until the bolt fits securely in the concrete (Figure 7-5). Connect a galvanized post anchor to the top of the expansion bolt, and then set the post or beam in the post anchor and tighten the nut.
[FIGURE 7-4 OMITTED]
Angle braces are fastened to concrete using expansion bolts, then lag screwed to a post or beam. Set the post in position and mark the location of the brace on the concrete surface. Drill pilot holes in the concrete the same depth and diameter as the expansion anchor bolt. Install expanding anchor bolts in the concrete and tighten securely with a wrench (Figure 7-5). Place the angle brace over the expansion bolts and tighten the washers and nuts.
Cast-in-Place Concrete Footings
Cast-in-place concrete footings provide a stable support for most types of structures. Structures are anchored to this footing using a galvanized post anchor that is set in the top of the footing while the concrete is still wet. Footing anchoring may allow the structure to twist and possibly collapse, so structures that have only posts for support will not work with this type of footing unless the structure is braced (Figure 7-6).
[FIGURE 7-5 OMITTED]
To construct a concrete footing, excavate a 12" diameter round hole to frost depth plus 6", centered on the footing-location marking. The hole should be as vertical as possible, with straight sides. A properly excavated hole does not require forms, but if you desire a neat appearance at grade level, a piece of paper form or a 12" x 12" square box constructed from 2 x 6's may be used to form the top 6" of the pour (Figure 7-7). Before pouring, recheck your measurements to verify that the footing is located in the proper position and elevation. If it is not, enlarge the hole or fill it and dig another in the proper location.
[FIGURE 7-6 OMITTED]
Reinforce the footing by cutting two #4 (1/2" diameter) reinforcing rods (rerod or rebar) 8" longer than the depth of the hole. Insert the reinforcing rod into the hole, pushing the extra length into the ground at the bottom of the hole until the rerods are below the top of footing (Figure 7-7). Place 2-3" of 1" crushed stone into the bottom of the hole for drainage. Mix and pour concrete into the hole and tamp gently with a stick or a shovel handle until it is settled, to work out any air bubbles that may be present below the surface. Fill to the top of the hole and smooth the top with a magnesium float. Slightly dome the top surface of the concrete to enable water to drain off it. Before your footing hardens, insert a galvanized post anchor into the center of the footing; be sure it remains vertical as the concrete hardens. After 24-hours any forming material may be removed from your footing.
If posts are placed on footings or piers, they should be braced and held in correct position until the structure will support itself. To do this, fasten two 1 x 6's, set at right angles to each other, to a post (Figure 78). Connect each 1 x 6 to a stake anchored in the ground. Each subsequent post can be braced in two directions in a similar manner or braced against posts previously anchored. Be sure that your project is square before placing any other components.
Direct Burial of Posts
For residential applications in locations with stable subsoils, you can bury treated support posts directly into the ground to provide adequate support for your structure. This type of support provides structural support, braces against twisting and, if buried to the proper depth, can provide protection against frost heaving. For direct burial of a post, excavate an 8" diameter hole 6" below maximum frost depth and centered directly on the footing location marking. The hole should be as vertical as possible, with straight sides. Place 2-3" of gravel at the bottom of the hole for drainage. To extend the life of a direct-burial post, wrap the post with asphalt building paper at the ground line to prevent contact with soil. The building paper should extend 6" above and 9" below finish grade, then staple it to the post (Figure 7-9).
[FIGURE 7-7 OMITTED]
[FIGURE 7-8 OMITTED]
[FIGURE 7-9 OMITTED]
Place the post in the hole, backfill halfway, tamp, and check with a level to ensure that your post is plumb and square. You can backfill with soil excavated from the hole, and the compressed soil will provide stable support of the post if the hole has not been dug too wide. Compact the soil with the handle of a shovel after every 8" of fill has been placed. Another choice for filling around a post is to place concrete in the void around the post. Although this method provides a very stable installation, it may trap moisture around the post, leading to premature decay.
Whichever choice of backfill you select, constantly check that the post is plumb as the hole is filled. Correct leaning posts by wiggling the post and applying pressure in the direction the post needs to move. Recompact after alignment is corrected, and backfill to the finish grade. If you select concrete for backfilll, smooth the concrete surface of the hole with a wood float, sloping the surface away from the post so that water will drain away from the post; this will help to prevent rotting of the post.
BUILDING WOODEN STRUCTURES
After making all the preliminary choices and decisions, the actual building of a wood structure may seem anticlimactic. However, if all the work has been properly done, the construction should proceed with minimal problems, and the rewards will last for many years. Two structures suggested for the homeowner to consider are arbors and trellises.
Arbors are open-roofed structures that are typically used for shade, to support vining plant material, or to accent entry points in the landscape. Composed of posts that support a framework of open roofing materials, arbors are one of the simplest ways to introduce an overhead enclosure into the landscape. The roof structure is not intended to be weatherproof and can be composed of any number of creative patterns or materials. Vining plant materials are a natural enhancement of the arbor landscape structure, and designs may have the arbor arcing over a walkway or enclosed on one or both sides along a walkway. When designed large enough to cover an outdoor use area, such as a deck or patio, arbors are sometimes termed shade structures.
Construction of a 4' x 8' overhead arbor Alternatives to this project: Arbors can be designed in several different forms and sizes. See Appendix A for alternative arbor sizes and designs and additional construction details. Alternative arbor 2 (Figures A-1 and A-2) is 8' x 8' with a lattice surface, and alternative arbor 3 (Figures A-3 and A-4) is 10' x 10' with an alternating 2 x 4 and 2 x 2 surface. CAUTION * The components of this project are sized for the design shown. Altering the size will require adjusting the size of the components to maintain structural integrity. * Verify that the footing depth is appropriate for your geographic region; if you are in an area in which the ground freezes during the winter, you may have to increase the depth of the footing so that it will extend below the frost line. * Use caution when operating power equipment. * Follow the manufacturer's instructions when using power equipment. * Use caution when climbing or working on a ladder. Time: 1-2 days. Level: Challenging (17 steps. Heavy lifting and carpentry skills required. Portions of the project will require two people. Tools Needed: 1. Plan of the project (Figures 7-10 and 7-11). 2. Marking paint. 3. Post-hole excavator (auger or clamshell. 4. Round-nosed shovel. 5. Wheelbarrow 6. 25' measuring tape. 7. Claw hammer. 8. Carpenter's saw. 9. Pencil. 10. Circular saw. 11. Electrical cords and connection to a GFCI power source. 12. Drill (cordless operation or electric) and drill bits (spade or auger, sizes from 1/8" to 1/2" and standard/phillips head screwdriver bits) 13. Wrench set. 14. 10' step ladder. 15. Carpenter's square. 16. Torpedo level. 17. Stapler. 18. Utility knife. [FIGURE 7-10 OMITTED] [FIGURE 7-11 OMITTED] Materials Needed (based on design shown, with lumber type and finish to be chosen by the builder: 1. Four 6 x 6 posts 12' long (length may be adjusted downward based on burial depth required for your geographic region. (Note: 4" x 4" posts may be substituted, with spacing adjustments, for other wooden structural members. 2. Four 2 x 10 beams 4'-0" long. 3. Four 2 x 10 rafters 8' long. 4. Seventeen 2 x 4 surfacing boards 4' long. 5. Sixteen 3/8" diameter x 10" long carriage bolts with washers and nuts. 6. Seventy #8 diameter x 5" long lag screws. 7. Fifty 16d (16-penny) nails or polymer-coated deck screws. 8. 5 cubic feet (CF) of 1" crushed stone. 9. Finish (stain or paint) selected by the builder. 10. Four 2" x 2" x 2' wood stakes. 11. Four additional 5' and 10' 1 x 4's to use as temporary bracing. 12. Four 15" wide x 15" long strips of building paper. 13. One box 1/4" staples. Directions: 1. If you plan to directly bury your support posts, attach a strip of building felt to each, as described in the previous section titled Direct Burial of Posts. 2. Find post locations on the plan (Figure 7-10). Paint a large x mark on the ground, with the center of the mark indicating where the center of the post will be. 3. Excavate each post location to frost depth for your area or to a minimum of 24" deep. 4. Place 1/2" CF of crushed stone in the base of the each hole. 5. Set one post in each hole. 6. Hold posts in correct position and, about 4' above grade, nail the 2 x 4 braces between the posts. Backfill the holes. Check the posts for plumb and proper spacing often (Figure 7-12). When completely backfilled, the posts should be plumb and spaced according to the plan. 7. With posts secure, temporarily nail the 4'- 0" 2 x 10 beams at the height shown in the front and side elevation drawings (Figure 7-11). 8. Drill holes through the 2 x 10 beams and posts at the locations shown. Install carriage bolts through the pilot holes and secure with washers and nuts. Repeat for all four posts. Remove the temporary nails Figure 7-13). 9. Position the 8' 2 x 10 rafters on top of the 2 x 10 beams as shown in the drawing and temporarily nail in position. Check the structure for square (that is, diagonal post-to-post measurements are equal) and level. 10. Drill holes through the 8' 2 x 10 and posts at the locations shown. Install carriage bolts through the pilot holes and secure with washers and nuts. Repeat for all four posts and remove the temporary nails. 11. With the carpenter's saw, trim the top of the posts flush with the tops of the 8' 2 x 10's. If you are using treated posts, retreat the cut ends. 12. Remove any temporary bracing. 13. Place the end 4' 2 x 4 surfacing on its edge on top of the 8' 2 x 10's in the location shown on the drawing. 14. At each location where the 2 x 4 crosses the 2 x 10, drill a pilot hole three-quarters of the way through the 2 x 4. (Note: it may be easier to mark one 2 x 4 to use as a pattern for the rest, then mark and drill the holes on the ground rather than on top of the structure.) 15. Insert a #8 x 5" lag screw through each pilot hole and twist it into the 2 x 10 using a wrench. 16. Repeat this installation of 2 x 4's for each location shown on the drawing (Figure 7-14). 17. Apply the finish you chose. [FIGURE 7-12 OMITTED] [FIGURE 7-13 OMITTED] [FIGURE 7-14 OMITTED]
Trellises are vertical structures with open frameworks, often with vining plant growth growing upon them. Trellises may be free standing or can be attached to walls, arbor posts, or the sides of structures. If creatively used, trellises can function as both a screen to hide undesirable areas and as a support for growing fruiting and flowering plants (Figure 7-15). When considering trellis designs, choose one that will have sufficient strength to support the weight of aggressive vining plants. People often don't recognize that the weight and growth habit of a mature vining plant is enough to cause a trellis to collapse.
[FIGURE 7-15 OMITTED]
Construction of a trellis Alternative to this project: Trellises can be designed in a variety of forms. See Appendix B for an alternative trellis. The alternative trellis (Figures 11-7 and 11-8), is a post-and-cable trellis that employs turnbuckles to keep the framework taut. CAUTION * Use caution when operating power equipment. * Follow the manufacturer's instructions on the use of power equipment. * Use caution when climbing on ladders. Time: 1-2 days. Level: Challenging (14 steps. Requiring physical exertion and carpentry skills. Portions of the project will require two people. Tools Needed: 1. Plan of project (Figure 7-16). 2. Marking paint. 3. Post-hole excavator. 4. Round-nosed shovel. 5. Wheelbarrow 6. 25' tape measure. 7. Claw hammer. 8. Carpenter's saw. 9. Pencil. 10. Circular saw. 11. Power cords and connection to GFCI power source. 12. Drill (cordless operation or electric) and drill bits (spade or auger, sized from 1/8" to 1/2", standard and phillips head screwdriver bits. 13. Wrench set. 14. 10' step ladder. 15. Carpenter's square. 16. Torpedo level. 17. Stapler. 18. Utility knife. [FIGURE 7-16 OMITTED] Materials Needed (based on design shown; lumber type and finish to be chosen by builder: 1. Three 4 x 4 posts 12' long (length may be adjusted downward based on burial depth required for your geographic region) 2. Four 4 x 4's 8' long. 3. Nineteen 2 x 2's 5' long. 4. Twelve 3/8" diameter x 6" long carriage bolts with washers and nuts. 5. Fifty 3" long polymer coated deck (or wood) screws. 6. Five cubic feet of 1" crushed stone. 7. Finish selected by builder. 8. Four additional 10' 1 x 4's to use as temporary bracing. 9. Four 2" x 2" x 2' wood stakes. 10. Fifty 16d nails. 11. Four 15" wide x 15" long strips of building paper. 12. One box of 1/4" staples. Directions: 1. If directly buried, attach a strip of building felt as described in the earlier section titled Direct Burial of Posts. 2. Determine post locations from the plan. Paint a large x mark on the ground, with the center of the mark indicating where the center of the post will be. 3. Excavate each post location to at least 6" below maximum frost depth for your area (a minimum of 24" deep. 4. Place 1/2" cubic foot of crushed stone in the bottom of each hole. 5. Set one post in each hole. 6. Hold posts in correct position and, about 4' above grade, nail a 2 x 4 between each of the posts as temporary braces. Backfill the holes. Check posts for plumb and proper spacing often. When completely backfilled, the posts should be in the position shown on the plan. 7. With posts secure, have an assistant hold the 8' 4 x 4's at the height shown in the drawing. 8. Drill holes through the 4 x 4's and posts at the locations shown. Install carriage bolts through the pilot holes and secure them with washers and nuts. Repeat at all locations where 4 x 4's intersect posts. 9. Remove the temporary bracing. 10. Place the edge 5' 2 x 2' vertically in front of the 8' 4 x 4's in the location shown on the drawing. 11. At each location where the 2 x 2 crosses the 4 x 4, drill a pilot hole, slightly smaller than the diameter of the fastener, through the 2 x 2. 12. Insert a 3" wood screw through each pilot hole and drive it into the 2 x 10 using the drill. 13. Repeat this installation of 2 x 2's for each location shown on the drawing. 14. Apply your chosen finish. Table 7-1 Softwoods Decay Kind Hardness Strength Resistance Uses Red Soft Low Very Exterior cedar high Fir Medium to High Medium Framing, millwork, hard plywood Ponderosa Medium Medium Low Millwork, pine trim Western Soft to Low Low Millwork, white pine medium trim Southern Soft to High Medium Framing, yellow pine hard plywood Redwood Soft Low Very Exterior high Spruce Medium Medium Low Siding, subflooring Table 7-1 Softwoods used in landscape construction. Table 7-2 Nominal and Actual Dimensions for Stick Lumber Nominal Actual Dimension Dimension 1 inch 3/4 inch 2 inches 1-1/2 inches 4 inches 3-1/2 inches 6 inches 5-1/2 inches 8 inches 7-1/4 inches 10 inches 9-1/4 inches 12 inches 11-1/4 inches Example: 2 x 12 actual dimensions are 1-1/2 inches x 11-1/4 inches. Table 7-2 Nominal and actual dimensions for dimensioned lumber.
|Printer friendly Cite/link Email Feedback|
|Publication:||Plan It, Dig It, Build It! Your Step-By-Step Guide to Landscape Projects|
|Article Type:||Professional standards|
|Date:||Jan 1, 2003|
|Previous Article:||Chapter 6 Landscape paving.|
|Next Article:||Chapter 9 Water, edging, lighting, and other site amenities.|