The A-Frame: Modern Tent Built with Plywood

Intro to Quick-and-Easy Backyard Building

Like Kubla Khan decreeing a stately pleasure dome, you can embellish your backyard Xanadu with a truly spectacular dome—or with a shed, an arbor, a tree house or a gazebo. But unlike the subject of Coleridge’s famous poem, you can carry out the decree personally and build the structure yourself. Moreover, you can build it with a minimum of time, labor and expense, since unlike the great Khan, you have available an astonishing variety of techniques. They make possible structures that, while not built for the ages, are sturdy enough to last for as long as you will want to use them.

Of the many methods available for building the quick-and-easy structures shown , some, like the post-and- beam, are older than the Pyramids; others, like the geodesic dome, are recent adaptations of ancient forms. But for all of them, you begin by erecting a skeleton. To build an A-frame, for example, you first erect inverted Vs of jointed timbers to serve as ribs of the combination roof-walls. Similarly, with post-and-beam buildings, you first raise the posts and then link them with horizontal beams. This technique—which man developed for his first wooden dwellings, refined for the Parthenon and still uses for skyscrapers—is strong, yet leaves large open spaces between the supports.

A structural skeleton alone may be enough for an arbor, but for a shade house you may want to add a partial covering and for a storage shed you need a weatherproof skin. Sheathing materials often do double duty: traditional wood and plywood combine sheathing with weatherproofing. Decorative lattice, bamboo, and woven-reed coverings also moderate the glare of sun and blast of wind. Easily installed screens keep out bugs but let in air and sunshine. Inexpensive plastic panels repel wind and water but admit light.

When you imaginatively combine decorative sheathings with fanciful frames, the whole structure becomes fun. The gazebo, a multi- sided post-and-beam structure, lends itself to the addition of lattices, curlicues and cupolas. As for tree houses, only the fertile imagination of youth is needed to convert an arboreal platform into a castle, a space ship or a frigate’s quarter-deck.

One type of lightweight structure is not an offspring of traditional construction at all, but the brain child of a 20th Century genius who figured out how to weave a web of triangles into the shape of the age-old hemispherical dome. Buckminster Fuller’s geodesic domes are based on the geometric shape called an icosahedron. Yet advanced mathematics plays no great role in dome-building—you can erect this lacing of struts as readily as a square shed, and people will admire your many-faceted pleasure dome even if they have never heard its technical name.

Ready for installation. Coverings suitable for sheathing light outdoor structures range from rolls of woven reed and lengths of bamboo to conventional screening and a crisscrossing frame work of wooden lattice. Designed for openness, these materials are so light in weight that in most cases all you need for fastening them to a structure is an ordinary staple gun.

The A-Frame: Modern Tent Built with Plywood

One of the simplest of all buildings takes the form of a braced triangle—an A-frame—rising from the ground. Nailed together at the peak of an A-frame, the rafters that serve as both roof and walls enclose a structure that's practical for many types of small outdoor buildings. A low A-frame, with a peak 3 to 5 ft. above the ground, might be used as a pet shelter or a storage shed; a higher one, with 6 or more ft. of headroom, can serve as a garden house or a playroom.

In every A-frame, the walls that form the roof are equal, but the angle at the peak may vary considerably, and this angle affects both headroom and floor space. A typical A-frame, like the one shown, is an equilateral triangle, with a base and sides of exactly the same length. A-frames with steeper sides have more headroom, but proportionately less floor space; flattening the triangle has the opposite effect.

Before you begin to build, decide upon the slope of the A-frame and , using a framing square (Step 2), mark angle cuts at the peak and bottom of each rafter. The slope is the ratio of the rise (the vertical distance from the base to the peak) to the run (the distance between the midpoint and the end of the base), expressed in inches of rise for every 12” of run. The roof of the A-frame has a slope of 21 in 12, but the framing square can mark rafter angles for any slope you choose.

The rafters of an A-frame, like those of any two-sided roof, must be reinforced to prevent spreading and sagging. In a small A-frame resting directly on the ground or on a bed of gravel, you can brace the rafters with crossties (called collar beams). In structures where head room is valued, the horizontal reinforcements can be built into the floor. If you intend to use your A-frame for storage alone, simply bolt the rafters to a rein forced concrete slab. In garden shelters or playhouses, sandwich the rafters between wooden joists, and install flooring.

A Compact, Triangular Structure

68 Anatomy of an A-frame. The rafters of this typical A-frame are 2-by-6s joined at their peaks with triangular plywood gussets (the gussets on the outermost rafters are omitted so that sheathing will lie fiat against the vertical walls). The bases of the rafters are fastened by metal anchor plates, and the sole plates on all four sides are bolted to a concrete slab. At the ends of the A-frame the vertical sides are framed with conventional 2-by-4 sole plates and studding, and the entire structure is covered with plywood boards and weatherproof sheathing.

69a Piers for a wooden floor. At the corners, concrete footings 12” thick, ‘ mortar beds and precast concrete piers serve as a foundation for 4-by-4 girders and 2-by-6 joists in an A-frame with a wooden floor. The girders, which are adequate for spans of up to 4½ ft., are toenailed to wood nailing blocks that fit into precast cavities in the tops of the piers; the joists, in turn, are toenailed to the girders and fastened to the rafters with %” machine bolts. The joists sandwiched around each rafter will brace the walls of the A-frame and provide a solid base for the flooring. For an A-frame with rafters that span more than 4½ ft., use doubled 2-by-6s, on edge, for girders.

Laying the Foundation

69b 1. Pouring the concrete. Empty the concrete for a small slab into a rectangular wooden form of 1-by-6 boards staked into the ground and enclosing a 6”-thick bed of gravel covered by 10-guage 6 x 6 wire reinforcing mesh. Use a mortar hoe to pack each load up against the preceding one, until the concrete comes lust over the top edge of the form.

2. Placing anchor bolts. When the concrete be gins to harden, embed 8” anchor bolts along the edges of the slab, leaving the top 4” of each bolt exposed above the concrete. Run a string along the sides of the slab 3¾” in from the edge and place the first bolt along the string, starting 8” from one end, and the remaining bolts at 32” intervals. On the front and back of the slab, place the first and last bolts 24” from the ends, the remaining ones at 32” intervals, 1¾” in from the edges, but leave a gap in the front row for a door.

When the concrete hardens, snap chalk lines 7½” from the sides of the slab and 3½” from the front and back to mark locations for the inner edges of the sole plates.

Building Roofs That Are Walls

70 1. Marking a sole plate. On each side of the slab, line up a 2-by-8 sole plate along the chalk line you snapped parallel to the anchor bolts and , using a framing square, transfer the positions of the bolts to the plate. To center the bolt-hole locations on the plate, measure the distance from the bolts to the edge of the plate and mark this distance off on the plate.

Mark the rafter locations on the plate between the bolt marks, setting the spacing for 16” centers and allowing for double rafters at both ends. Finally, set the plate on a second 2-by-8 cut to the same length, drill through both plates at the spots marked for anchor bolts and bolt the doubled plate in place on the slab.

2. Marking angle cuts.

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3. Using a jig. Saw the rafter-board ends with a circular saw in a homemade cutting jig consisting of two 2-by-4s nailed onto a plywood board. To make the jig, space the 2-by-4s 5½” apart (the width of a 2-by-6 rafter board). Slip the marked rafter board between the 2-by-4s and nail a 1-by-4 guide to them, at an angle that matches the angle cut you have marked for the top of the rafter. Check to be sure that the blade of the saw cuts along the rafter mark.

Use the jig to cut the bases of the rafter boards by realigning the 1-by-4 to match the angle you have cut for the rafter base.

4. A-joints. Set pairs of rafters together on the ground to form roof peaks, and nail triangular ply wood gussets on both sides of the peak joints, using exterior-grade 5 plywood cut to the same angle as the peak. Drive at least six four- penny nails in a triangular pattern to make the joint secure. Caution: do not nail gussets to the outsides of the front and back peaks.

72 5. Setting the first A. With a helper, raise a pair of double rafters into position over the marked locations at the end of the sole plate. Brace the rafters temporarily with a scrap 2-by-4 nailed to a stake about 5 ft. from the slab. Use a carpenter’s level to be sure the rafters are plumb.

6. Attaching the anchor plates. Fasten rafters to the sole plates with metal anchor plates fastened to both sides of a rafter w b four penny nails; for additional stability, toenail two eight-penny nails through the outside edge of the rafter into the sole plate. When you have anchored and plumbed three sets of rafters to the sole plate, install temporary stiffeners—horizontal 1-by-2s nailed into the rafter edges—to keep them steady.

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7. Sheathing the rafters. Nail 4-by-8 panels of 5/8” exterior plywood horizontally along the rafters. Begin at the outer edge and bottom of the first rafter. Nail the corners of a panel first, then nail through all the rafters beneath, spacing the nails 6” apart. After you have completed the bottom row of sheathing, remove the temporary stiffening and complete the rest of the side. Stagger the joints between plywood boards by cutting the first board of the second row to end at the midpoint of the board below.

8. Studding the end walls. Bolt doubled 2-by-4 sole plates to the anchor bolts at the front and back ends of the slab, then install studs for the front and back walls on 16” centers, toenailing each stud to the sole plate below and the rafter above. Leave a space for a door in the stud ding of the front wall; frame the space with jack studs, a header and cripple studs in the front wall. Saw off the sole plates in the door opening and sheathe the ends of the A-frame.