Measuring and Marking Fences
Even the simplest fence will require a variety of measuring tools. You will probably use your tape measure most often. Get into the habit of starting work by clipping a steel tape to your belt.
There’s an old carpenter’s adage that says “measure twice, cut once.” It’s been around for years with good reason—it’s amazingly easy to misread a measurement, even if you’re a pro. Don’t take anything for granted when measuring; mistakes waste time and material.
You’ll need a sharp-pointed pencil to make accurate marks on your material. Carpenter’s pencils, which have flat rather than round leads, work well for marking wood. For more accuracy use an awl, which looks like a short ice pick, or a scriber, which resembles a long steel toothpick.
Saw on scrap side
Although you may make most rip cuts with a table saw, if you use a circular saw, equip it with a rip-cutting guide and make sure the guide does not wander off the edge of the board.
Saw on the scrap side of the cutoff line, not straight down the middle of it. Otherwise your board will be half a saw kerf shorter than the length you want. Even this small discrepancy—typically 1/2 inch—can make a big difference.
Using squares and levels
Square refers to an exact 90-degree angle between two surfaces. When a material is level, it’s perfectly horizontal; when it’s plumb it’s truly vertical.Never assume that existing construction is square, level, or plumb. It probably isn’t. To prove this to yourself, lay a level horizontally along any floor in your home, hold a level vertically against a wall section in a corner, or place a square on a door or window frame. Don’t be alarmed at the results. Variation is normal because houses and other structures settle slightly on their foundations, throwing off square, level, and plumb.
How can you check a level’s accuracy? Lay it on a horizontal surface and shim it, if necessary, to get a level reading. Then turn the level end for end. If you don’t get the same reading, the level needs to be adjusted or replaced. Some models allow you to calibrate the level by rotating the glass vials. Laser levels come with instructions for their calibration.
Use a combination square, layout square, or T-bevel to mark angles. A combination square and layout square can make only 45- and 90-degree angles. A T-bevel allows you to duplicate any angle and transfer it to the surface you’re cutting. For large squaring jobs use a framing square, setting it on the inside or outside of the corner as the framing allows.
Fence posts must be plumb in two vertical planes, and a post level is made specifically for this job. Strap the level about halfway up the final length of the post. Adjust the post until all three bubbles are centered in their vials. The longer the level the more precise your alignments will be. Use a 4-foot carpenter’s level unless you don’t have room. Use the end vials to plumb a board, the center vial to check for level.
Laying out a fence and setting posts
- TIME: About 8 hours, depending on length of fence and number of posts
- SKILLS: Measuring, marking, carpentry
- TOOLS: Circular saw, drill/driver, small sledge, masons line, plumb bob, tripod, posthole digger, wheelbarrow, shovel, hammer, level, concrete hoe, tamper
Laying out a fence line is the first, and perhaps the most critical, step in constructing a fence. Do this correctly and the rest of your construction will proceed smoothly.
The illustrations on these pages show the essential steps in locating and lining up your posts. Before you start check with the city or county zoning office to make sure your project will comply with building codes and ordinances regarding setback from your property line. Most locations have a single phone number you can call to have the buried pipes and wires on your property located and marked before you dig. Your local electric utility may provide the number.
Build batter boards from 2x4s by fastening crosspieces to the legs and driving them into the ground 3 to 4 feet beyond the ends of your fence line. Drive another pair of batter boards perpendicular to the first fence line to your next post location and mark its center with the same technique. Continue staking the post centers until you have marked all of them.
Starting at the intersection of the lines, measure 3 feet (or a multiple of three) out on one line and mark that point with a piece of tape. Measure 4 feet (or the same multiple) on the other line and mark it. Measure the distance between the pieces of tape. If the diagonal measures 5 feet (or the multiple), the corner is square. If necessary, adjust the lines until they make a 5-foot diagonal. Mark the final position of the lines on the crosspieces.
You’ll need several pieces of equipment to lay out a fence line. To visualize the layout, use a tape measure and a garden hose to outline its dimensions on the ground. Then gather and cut the lumber for the batter boards. You will need a small sledge hammer to drive the batter boards into the ground, a cordless drill/driver, a plumb bob, a camera tripod, a spool of mason’s line, and deck screws to assemble them.
Remove the mason’s lines from the batter boards (to get them out of your way).Then dig the postholes and shovel 3 inches of gravel into each one. The gravel lets water drain away from the bottom of the post and reduces the opportunities for rot. Set the post on the gravel and support it with temporary braces.
In general, and in most areas of the country, posts anchored in concrete are the best way to support a fence or gate. However, in frost-free regions and in some soils, you can set the posts in a tamped earth-and-gravel base. Local building codes may have advice or standards about setting posts so check with your building department before digging the holes.
Define each corner with a pair of batter boards. For each batter board make a pair of stakes by cutting a point on one end of two 2x4s. Attach a crossbar (see Step 1 on page 42) and drive the batter boards into the ground 3 to 4 feet outside the planned corner location. Locate them so that a line connecting the posthole center lines will be at about the center of the crossbar.
However you decide to set your posts, be sure to dig holes for them 6 inches deeper than the frost line in your area to counter the effects of frost heave. Dig an 8-inch-diameter hole for each 4×4 post using a power auger, hand auger, or posthole digger (see pages 22-23). A 6×6 post requires a 10-inch-diameter hole.
Plumb and align posts
Replace the mason’s line on the batter boards, placing it outside the original marks by one-half the thickness of the post (1% inches for 4×4 posts). This will position the line at the outside face of the posts. Working on one post at a time with a helper, loosen the temporary braces and plumb each post with its outside face against the line. You can set the posts Vs inch inside the line to avoid moving the line with the posts. Attach braces to hold the posts in position.
Unless you are constructing an extremely long fence, consider using premixed bags of concrete that come with the correct amount of sand and gravel added to the cement; all you do is add water and mix. Premixed bags also make it easier for you to set some of the posts one day and come back the next day to set the rest of them without having your work schedule dictated by unused concrete. You can also buy the cement in bags, order sand and gravel, and mix the concrete yourself. Mixing it yourself is less expensive but is more work. The convenience of premixed concrete is usually worth the extra money. I n either case you will need gravel for the bottom of the postholes.
For most post-setting projects, mix three parts gravel with two parts sand and one part cement. If you mix your own concrete, move the mixing container as close to your posts as possible so you won’t have to haul concrete across the yard in a wheelbarrow. The amount of water needed depends on how wet the sand is. You’ll need less water with wet sand than with dry sand. Test the wetness by squeezing some sand in your hand. If water seeps out, you’ll need to add less water to the mix. If the ball compacts like moist clay, the mix will take more water.
As you mix the concrete, add very small amounts of water at a time. When the mix becomes one color— medium gray—and sticks slightly to a shovel held almost at 90 degrees, it’s ready. Once the concrete has cured, mark the height of the posts and cut them with a reciprocating saw (see illustration, opposite).
Although setting posts in concrete is the most common method of anchoring them, there are a couple of alternatives. In some localities you can dig the holes and set the posts in tamped earth and gravel. And with a drive-in post anchor like the one shown (below right) you don’t have to dig holes.
Setting posts in tamped earth and gravel
As with posts set in concrete, dig holes deep enough to go 6 inches below the frost line, then place several inches of gravel in the bottom of the holes. Posts in shallow holes or without the gravel can easily be knocked out of plumb.
Set a post in place, plumb it, and brace it with diagonal braces as shown on page 43. Then shovel about 4 inches of soil into the hole on all sides of the post and tamp it firmly. (A length of 2×4 makes a good tamper.) Follow this layer with a 4-inch layer of tamped gravel, alternating the earth and gravel until you’ve filled the hole. Then mound and tamp the soil around the base of the post; sloping the soil lets water drain away from the post and minimizes chances for rot. After several rainfalls check the slope. If the soil has settled, rebuild it and firmly compact it.
Anchoring posts to a patio or deck
If you’re building a fence along the edge of a patio, deck, or porch, metal post bases will provide you with a handy answer to the question, “How do I anchor them?” Some post bases are made to be embedded in wet concrete. Others fasten to bolts in new or existing concrete. Some of these are adjustable and raise the bottom of the post about 1 inch off the concrete, which keeps the foot of the post above ground moisture and puddled water, reducing the risk of rot.
To install a bolt in existing concrete, drill a hole in the concrete, then inject epoxy cement into the hole with a syringe that comes with the epoxy. Set the bolt so that the end extends about 3/4 inch above the surface.
After the epoxy cures, secure the base with a nut and washer. Then position the post in the base and nail or screw it in place. You can also use metal anchors to join posts to another wooden structure such as a deck or porch. Just nail or screw the base to the surface. A simple U-shape base will work where no moisture protection is necessary.
When building and anchoring a structure, keep these points in mind:
- Check local building codes for specific requirements.
- Don’t build a fence on an existing patio or deck without attaching one end to the house, permanent structure, or post embedded in the ground. Ideally a deck or patio fence should be anchored at both ends.
- Always use the fasteners specified for the base.
To set posts in soil, lay a gravel base, then shovel soil into the hole, filling it partially. Tamp the soil fill to compact the earth firmly around the post. Alternate layers of soil with layers of gravel, tamping every layer for a solid fill. A spike post base drives into the ground without digging. The length of the spike depends on the height of the fence. Make sure local codes allow this kind of base for your fence posts