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Checks
- Full of wet laundry, each 15 ft line pulls on the arms with about 63 lb; 4 lines, about 250 lb on each post top.
- Lines are 10 11/16″ apart on the arm.
- Keep the lines clear of paths, driveways and overhead wires, and well away from anywhere a mower or trampoline goes.
Shopping list
| Qty | Item | Est. |
|---|---|---|
| 3 | 4×4 pressure-treated post, 10′ (board) | $48.00 |
| 4 | Concrete mix, 80 lb bag (0.6 cu ft) (bag) | $26.00 |
| 2 | Crushed gravel (0.5 cu ft bag) | $12.00 |
| 1 | Wood stakes, 18″ (bundle of 12) | $9.00 |
| 1 | Mason's line (nylon string), 250′ (roll) | $6.00 |
| 1 | Plastic sheeting, 10′ × 25′ (for curing concrete) (roll) | $12.00 |
| 4 | Galvanized 6″ T-strap with screws (each) | $16.00 |
| 1 | 5/16″ × 6″ structural wood screws (box of 12) | $24.00 |
| 8 | 3/8″ × 6″ galvanized eye bolt, nuts and washers (each) | $32.00 |
| 4 | 3/8″ hook-and-eye turnbuckle, galvanized (each) | $20.00 |
| 16 | 1/8″ wire rope clip, galvanized (each) | $24.00 |
| 1 | Clothesline, vinyl-coated steel core, 100′ (roll) | $15.00 |
About $244 · rough estimates, check the store
Parts
| Part | Qty | Length | Width | Material | |
|---|---|---|---|---|---|
| A | Post Ground-contact rated. 24″ goes in the ground. | 2 | 92 1/2″ | 3 1/2″ | 4×4 pressure-treated post |
| B | Cross-arm | 2 | 36″ | 3 1/2″ | 4×4 pressure-treated post |
| C | Arm brace Cut both ends at 45°, parallel, long point to long point. | 4 | 19 7/8″ | 3 1/2″ | 4×4 pressure-treated post |
Cut list
2 × 4×4 pressure-treated post, 120″ → A 92 1/2″ · C 19 7/8″ each
4×4 pressure-treated post, 120″ → B 36″ · B 36″ · C 19 7/8″ · C 19 7/8″
Kerf 1/8″ included. Every cut runs edge to edge.
Steps
- Tape measure
- Speed square
- Pencil
- Drill/driver
- Clamps
- Safety glasses
- Hearing protection
- Dust mask
- Circular saw or miter saw
- Miter saw, or circular saw in two passes, for 4×4 posts
- Post-hole digger
- Wheelbarrow and hoe
- 4 ft level
- Drill with a 3/8″ bit long enough to pass 3 1/2″
- Wrenches for the eye bolts and rope clips
- Socket or impact driver for the 6″ structural screws
- Sander, 120 and 180 grit
1Before you start
Read every step once, start to finish, before you buy or cut anything. Each step names the parts it uses by letter; the parts list gives their sizes.
Set up somewhere flat with good light. A pair of sawhorses with a sheet of plywood on top makes a fine work table.
Wear safety glasses whenever a tool is running, hearing protection for saws, and a dust mask for sanding and for cutting treated wood or sheet goods. Tie back long hair and loose sleeves. Keep children and pets out of the work area.
- Tip At the store, pick straight boards: hold each one up to your eye and look down its length. Skip boards that bow, twist or have big knots near the ends.
- Tip Measure twice, cut once. Most mistakes are a misread tape, not a bad cut.
2Cut and label the parts
Cut every part on the cut list. Cut the longest parts first: if one goes wrong, it can still become a shorter part.
To mark a cut, hook your tape on the end of the board, make a small V with its point exactly at the measurement, and draw a square line through the point with a speed square. Put an X on the waste side.
Cut on the waste side of the line, so the blade's kerf (about 1/8″) comes out of the scrap, not your part.
Write each part's letter in pencil on a face that won't show, and stack the parts by letter.
Sand the faces before assembly while they're flat and easy to reach: 120 grit, then 180.
✓ Lay the parts out and count them against the parts list. Measure a few: if one is off by more than 1/16″, recut it now.
STOP. Let the saw reach full speed before it touches the wood, keep both hands clear of the blade's path, and never reach under a board you're cutting. Support long boards on both sides of the cut so the blade doesn't pinch.3Call 811 and check the spot
At least 3 working days before you dig, call 811 (or use call811.com). It's free. They send people to paint or flag buried gas, electric, water and cable lines near where the clothesline posts will go.
Check your property line on your survey or plot plan, and ask your town about setbacks, easements and whether this needs a permit.
Pick ground that drains: not a low spot where puddles sit after rain, and not over a septic field.
STOP. Don't dig until the marks are down. Hitting a gas or power line can kill you and is expensive to repair.4Mark the two posts
Pick a sunny, open strip with 15 ft of clear ground plus 3 ft past each end for walking round the posts. Hang laundry where the wind blows along the lines rather than across them, if you can.
Drive a stake for the first post centre. Measure 15 ft (180″) to the second and drive another. Run a string between them a few inches off the ground: the arms will sit square to this string.
Check the strip has no hidden slope that puts one post lower: lay a long straight board and level along the string, or use a line level on a tight string between the stakes.
✓ The stakes are 180″ apart centre to centre and the strip between them is clear.
5Dig the post holes
Dig 2 holes 10″ wide and 30″ deep with a post-hole digger.
That depth is 24″ for the post plus 6″ of gravel underneath so water drains away from the post end.
Make the holes slightly wider at the bottom than the top, like a bell. Frost then can't grip the concrete and lift it.
Pour 6″ of gravel in each hole and tamp it with the end of a 2×4 or the post itself.
- Tip Your town knows the frost depth: it's how deep footings must go so winter frost can't push them up. Enter it in the options and the holes will be dug deep enough.
✓ Every hole is 30″ deep before the gravel and 24″ deep after it.
6Set the posts plumb
Stand a post in each hole. Run a string between the end posts at the height you want, to line up the ones in between.
Hold a level against one face of a post until the bubble is centred: that face is plumb. Then check the face around the corner. Both faces must read plumb.
Brace each post with two 1×4 or 2×4 boards: screw one end to the post and the other to a stake hammered into the ground, one brace on each of two sides at right angles.
✓ Every post is plumb on two faces, in line with the string, and the braces hold it there when you let go.
7Lean the posts back a little
Loaded lines pull the two post tops toward each other with about 250 lb. Over the years that leans them in. So set them leaning slightly the other way to start with.
With the post plumb and braced, loosen the brace on the side facing the other post and push the top 3/4″ away from the other post, then re-tighten. Check with the level: the bubble sits just off centre, the same way on both posts.
Keep the post square to the line between the posts: the arm will sit across the top, and it must end up square to the lines.
- Tip When the lines are tight and loaded, the posts pull back toward plumb. Better a hair out than a hair in.
✓ Both posts lean out by the same small amount, and a string from post to post runs square across both tops.
8Mix the concrete
You'll use 4 bags of 80 lb concrete mix for the 2 post holes. Mix one or two bags at a time in a wheelbarrow: concrete starts to stiffen in about 30–45 minutes (faster on a hot day), so only mix what you can place right away.
Pour about 2 quarts of clean water into the wheelbarrow first, then empty one bag on top. (Each 80 lb bag needs about 3 quarts in total.)
Mix with a hoe or square shovel: pull the dry powder from the corners and bottom into the wet middle and chop through it. Keep going until there are no dry pockets.
Add the last of the water a cup at a time, mixing between each.
Get the thickness right. It should look and feel like thick oatmeal or stiff peanut butter. A hoe dragged through leaves ridges that stand up, and a handful squeezed in a gloved hand holds its shape. Too dry: it crumbles and won't stick together, so add a little water. Too wet: it flows flat, water pools on top, and the concrete will be weak and crack. Then add some dry mix from a spare bag.
- Tip More water makes concrete easier to push around and much weaker. Resist the urge.
- Tip Rinse the wheelbarrow, hoe and shovel before the concrete sets on them. Don't wash concrete into drains or onto the lawn: let leftovers harden in a scrap box and throw them out.
- Tip Buy one more bag than you need. Running out halfway through a pour is the most common mistake.
✓ Even grey colour throughout, no dry powder, no puddles of water on top; a ridge made with the hoe stands up.
STOP. Wet concrete is caustic and burns skin. Wear waterproof gloves, safety glasses, long sleeves and long pants. Open bags slowly and wear a dust mask: the dust has silica. Rinse any concrete off your skin right away.9Fill the holes
Shovel concrete into each hole around the post. Every 6″ or so, poke it hard with a stick or a piece of rebar to work out air pockets.
Fill to about 1″ above the ground and shape the top into a little mound with a trowel, sloping away from the post so rain runs off.
Check plumb again on both faces while it's still wet, and adjust the braces if needed.
✓ Posts are still plumb and in line after the concrete is in.
10Let the concrete cure
Concrete hardens by reacting with water, not by drying out, so keep the concrete around the clothesline posts damp for the first 7 days: mist it with a hose morning and evening, or cover it with plastic sheeting held down at the edges.
Keep it from freezing for the first week. Don't pour when it's below 40°F (5°C) or frost is forecast in the next two days. On hot days, pour in the early morning and shade it.
You can walk on it or remove braces after 1–2 days. Wait 3 days before putting real weight on it. It reaches full strength in about 4 weeks.
✓ The surface is hard and grey-white when dry, with no powder when you rub it.
11Fit the cross-arms and braces
Check each post top is level both ways. Saw it flat if not.
Centre a cross-arm (B) on top of each post, square to the string between the posts. Screw a galvanized T-strap across the joint on both faces (the faces looking along the line), using every hole.
Fit a brace (C) under each side of each arm at 45°: long points 14″ down the post and 14″ out along the arm. Predrill and drive a 6″ structural screw through each end.
Sight from one arm to the other: they should line up, both square to the line and both level.
✓ Both arms are level, the same height, square to the line, and don't move when you hang your weight on an end.
STOP. Don't hang on the arms until the concrete has cured for at least 3 days.12Fit the eye bolts
Mark 4 points along each arm, 10 11/16″ apart, the outer ones 2″ from the arm ends, on the face that looks toward the other post. Mark both arms the same.
Drill a 3/8″ hole straight through the arm at each mark, at mid-height, pointing at the other post.
Push an eye bolt through each hole from the inside (the face toward the other post), so the eye faces the line. Put a washer and nut on the back and tighten until the washer bites into the wood.
✓ 8 eye bolts, each straight and tight, lined up across from its partner on the other arm.
13String and tension the lines
Open each turnbuckle by unscrewing its ends until there is about 1″ of thread left in the body. That gives you room to tighten later.
Hook the turnbuckle onto an eye bolt on the first arm. Thread the line through the turnbuckle's other eye, fold 6″ back on itself, and clamp it with two wire rope clips 2″ apart. The clip's U-bolt goes on the short tail end, the saddle on the long line: "never saddle a dead horse".
Pull the line to the matching eye bolt on the other arm, thread it through, pull it as tight as you can by hand, fold it back and clamp it with two clips the same way.
Now turn each turnbuckle body until the line is tight. An empty line should sag about 1″ in the middle; it will sag several inches more when full.
- Tip Lines stretch in the first few weeks. Tighten the turnbuckles again after a month.
- Tip Wipe the lines with a damp cloth before the first wash so they don't leave a grey stripe on the laundry.
✓ Every line sags about the same and none touches its neighbour when you push it sideways.
14Finish
Ease every sharp edge and corner with 120-grit sandpaper so nobody gets a splinter.
Sand all over with 180 grit, always along the grain (the direction the wood fibres run). Scratches across the grain show through stain.
Wipe off the dust with a barely damp rag and let it dry.
Outdoors, use an exterior finish: a penetrating deck oil or exterior stain, or primer and exterior paint. Leave cedar bare to weather silver if you like. If it holds soil for food plants, leave the inside unfinished.
Let it dry for the time on the can before using it.
- Tip Try your finish on a scrap of the same wood first: stain looks different on every board.
Conceptual layout, material estimate and assembly guide from the sizes you entered. Not engineering, not a building plan, not stamped or approved. Confirm measurements on site; follow local codes and product instructions; anchor tall pieces before use. Using this plan means you accept the Terms of Use.