Building a flat-rail frame
Although building a flat-rail frame involves essentially the same techniques as building edge-rail framing, a few details need additional attention:
Because one of the functions of the top rail is to tie the posts together in a single structural unit and because joints reduce the top rail’s strength, you should minimize the number of joints. For rail stock get the longest boards possible. On a short fence a board that will span the entire length of the fence is ideal. On long fences always use top-rail stock long enough to span at least three posts.
- Always butt top rails on the center of a post. This adds strength to the joint and gives you a surface wide enough for your fasteners. The same goes for cap-rail stock. If you’re installing a cap rail, you can attach it at any time in the process of building the frame (but after fastening the top rail).
- Consider adding a cap rail to the fence design. This second top rail gives the fence a finished look and adds strength to the frame. Combined with a kick board, this can minimize fence sagging.
Posts and rails contribute to the overall look of the fence in a flat-frame fence with inset infill. If the fence will be painted, pressure-treated posts and rails work well. But if you are installing inset cedar or redwood infill that will be stained or left natural, you will probably be happier with posts and rails of the same lumber.
Lay out the fence line and set the posts in concrete. Let the concrete cure and leave the braces up—they add stability. Cut the posts to the correct height and measure down from the top of each post to mark the location of the bottom rails.
For fences on level ground, you can mark the end posts and snap a chalk line to mark the intermediate posts. For stepped or contoured frames, you’ll have to measure and mark each pair of posts separately.
Although flat rails are by nature more prone to sag than edge rails, there are a couple of things you can do to shore them up. A kick board mounted under the bottom of the lower rail and toenailed at both ends to the posts will add strength to the bay and help keep the whole assembly from sagging under its own weight. Adding one or two additional rails within the bay will also minimize sagging.
Because you might find it difficult to set a kickboard in the space between the bottom rail and the ground after the rail is fastened, screw the kickboard to the bottom of the rail first and then toenail the assembled pieces between the posts. As with edge rails, you can set flat rails at various heights from the ground and in dadoes cut in the interior faces of the posts. Varying the height of dadoed rails from bay to bay can add style to the backside of the fence.
Installing a kickboard
Kickboards close the gap under the bottom rail, add a decorative touch to your fence, and keep animals from crawling under it. They also help keep flat rails from sagging. You can attach them to the faces of the posts or inset them under the bottom rail. It’s usually easier to install an inset kickboard on the bottom rail and toenail the entire assembly to the posts. Grooving the bottom rail to accept the kickboard is an option. Fasten the kickboard to the bottom of the rail with 3-inch screws every 8 to 10 inches. Toenail it to the posts at the ends. Trim your kickboard with a 1×2 if you want. Make the kickboard from pressure-treated lumber or the heartwood of a decay-resistant species such as cedar or cypress because the board touches the earth and is subject to rot.
Installing surface mounted infill
Of all the aspects of fence construction, installing the infill is probably the most enjoyable because you can begin to see the results of your planning and layout. It’s at this step that the structure you’ve been toiling over begins to look like a fence. The tasks associated with hanging the infill are repetitive—you’ll fall into a rhythm and the work will go quickly.
Surface-mounted infill requires less measuring and fitting than inset infill so fences built this way go up quickly. You don’t even need to precut boards to length for surface-mounted infill when fencing on level ground; you can let the boards run wild—at random heights— and then cut them to a finished line all at once. Infill boards finished with a cut top—pickets, points, or dog ears, for example—must be cut to size before you put them up. If the infill is spaced, like pickets, make a jig to ensure consistent spacing. A board ripped to the correct width is an easy way to gauge spacing. Build the fence frame and let the concrete set. Tack a 1 x4 batten to the posts (spanning at least 3 bays) where you want the bottom of the infill. When you install the infill, set each board on the batten. This will keep the infill at a consistent
height above the ground.
It is tricky to get the bottom of each board lined up with the adjacent one. Tack a batten along the bottom of the posts—spanning at least three posts—and this task becomes a snap. The batten allows you to set each infill board directly on it—it’s like having a third hand. Level the batten if the ground is level; let it follow the slope for a contoured fence. Whether level or sloped, keep the batten at the same distance from the ground along its length by measuring and marking its location from the top of the posts. Don’t try to eyeball the clearance between the ground and the batten— it’s almost impossible to get it right without measuring.
- If your fasteners are less than 2 inches from the ends of the infill boards, predrill holes to keep the infill from splitting. Fasteners 2 inches or more from the ends of the infill are less likely to split the wood, but it’s still wise to drill pilot holes.
- If the infill goes out of plumb, remove it and correct the problem-it’s easier in the long run to fix a mistake early than to try adjusting subsequent boards.
■ Mark the height of your infill on both ends of the bay, snap a chalkline between the marks, and trim the infill along the line. To cut it quickly and accurately with a circular saw, measure down from the chalkline a distance equal to the distance from your circular saw’s blade to the edge of its soleplate. Watch out for uneven joints; they will catch the saw.
■ If you will be staining or painting the fence, prepare the surfaces according to the finish manufacturer’s instructions and apply the finish. Protect your landscaping and plantings with plastic tarps.
Mark the finished height of the completed infill at both ends of the fence, tack a guide to the fence, and trim the infill with a circular saw.
Installing inset infill
Inset infill lends itself to many fence styles: this is the ideal way to install lattice panels as well as other types of panel fencing—plywood, acrylic, and tongue and groove. You’ll also use it if you’re building a basket weave or featherboard fence. With its lx or 2x stops containing the infill boards and functioning as trim, it creates a stylish finished look for a variety of materials. Inset infill requires careful marking of the position of the stops and more exacting construction, but it produces clean lines and shows an equally attractive face on both sides. It’s the ideal construction if you’re looking for a friendly fence that will appeal to your next-door neighbors.
Your planning should include careful computation of the total width of the infill boards and stops. Because a 2×4 rail is actually 5/5 inches wide, you’ll have to make sure of two things:
- That the combined width of the materials does not exceed the width of the rails.
- That the entire assembly, infill boards and stops together, is centered in the frame.
Add the width of the pieces together and subtract it from the width of the rails. Divide the remaining amount in half: This is the width of the reveal on each side, the space between the stop and the edge of the rail. The combined width of lx infill and two lx stops— 2 inches—leaves VA inches of rail exposed on a 3/2-inch rail. Set your first stop vs inch from the edge of the rails (half of VA inches = 5/5 inch). Use a combination square set to 5/2 inch to mark each interior corner of the frame. Snap chalklines at these marks and nail the stops on the lines. Inset infill calls for a square fence frame, but you can usually work around minor flaws. Wide stops, for example, can hide gaps. And you can cut sheet materials to fit exactly.
Building board on board
Board-onboard fences are constructed slightly differently than other fences with inset infill. They require only one stop in the center of the frame to separate the infill boards on each side. Mark the location of the stop on the posts and rails, fasten the stop, and toenail the infill to the rails.
Infill installation tips
Following a few general tips will make any fence style more professional looking and longer lasting.
- Don’t scrimp on fasteners—either in quality or quantity. Treated nails or deck screws cost slightly more but will last longer and stain the fence less than untreated fasteners. Galvanized fasteners are not immune from rust. Stainless-steel fasteners are the best choice.
- In addition to their own weight, fences have to carry the loads imposed by rain, snow, wind, and climbing kids. Much of this stress falls on the fasteners—use plenty of them.
- Hang boards plumb. Check the infill as you go—every few feet at least— with a 4-foot level (shorter levels won’t be accurate). If the infill has gotten out of plumb, take your work apart and correct it. Out-of-plumb infill only gets worse.
- Make bottom edges flush and smooth. Use battens to help place the infill (tack a 1×3 or 1×4 to the surface of the posts) unless your design intentionally calls for random lengths. Reposition the batten as you work your way down the line.
- To finish a wild-top edge, snap a chalkline at the cutting height. Then tack a 1×3 or 1×4 guide so a circular saw’s soleplate can ride on it. Set the blade deep enough to cut through the infill, but no deeper. Rest the saw on the cutting guide and cut the entire top of the fence in one pass.
Spacing the infill
Equalize the spaces between infill boards with a cleated spacer. Hang the cleat on the top rail so you can free both hands to hold the infill as you fasten it. Check the infill for plumb every 3 or 4 feet.
Cutting angled infill
Cut templates to properly position angled infill in the frame. Cut the bottom of the infill to the correct angle and set the boards on a level batten while you fasten them. Cut the top edge to length or let the tops of the boards run wild and trim them with a circular saw. Use another batten to guide the saw and keep the top edge straight.