A clothesline is one of those satisfying weekend projects that looks simple until you start digging and realize the holes are deeper than expected and you need more concrete than you thought. The standard 10-inch hole at 36 to 42-inch depth for a residential clothesline post holds between 1.6 and 1.9 cubic feet of concrete per hole — that is 4 to 5 bags of 60 lb concrete per post, or 8 to 10 bags for both posts combined. Mixing 10 bags of concrete by hand in a bucket on a hot summer afternoon is a workout. The Quikrete Fast-Set dry pour method cuts the work in half: pour the dry mix into the hole around the plumbed post, pour about a quart of water slowly over the top, and in 20 minutes the post is locked in place. Move on to the second post while the first one stiffens. Done.
The thing that separates clothesline post installation from other post jobs is line tension. A clothesline loaded with wet laundry — a family wash on a Monday morning — can weigh 40 to 80 pounds of wet fabric. That weight pulls the line down and outward, transferring an outward lateral force to the top of each post. On a standard 18-foot span in firm soil with 36-inch deep concrete footings, the post handle this force easily. On a long span of 24 feet or more, or in loose sandy soil, the posts can gradually lean inward over the years. The traditional solution is simple and elegant: install each post with a 5-degree outward lean toward its own side, away from the center of the line. When the line is loaded, the lean counters the pull and the post ends up plumb. Our calculator flags this for medium and long spans so you know about it before the concrete goes in.
Volume per hole equals pi times (hole radius in feet) squared times depth in feet, times 1.10 waste factor. The calculator always assumes 2 posts and shows per-post and total-for-both results simultaneously. Fast-Set 50 lb bags cover 0.375 cubic feet each; standard 60 lb covers 0.45 cubic feet; 80 lb covers 0.60 cubic feet. The depth check compares your entered depth to one-third of the total post length (above grade plus burial). The span tension check uses 15 feet as the short/medium threshold and 25 feet as the medium/long threshold, with appropriate installation notes for each range.
01
Use the Lean-Back Method for Spans Over 15 Feet
The traditional clothesline post installation method intentionally tilts each post 5 degrees outward — away from the center of the line — so the post ends up perfectly plumb when the line is loaded with wet laundry. When the concrete is freshly poured and still wet, brace each post leaning slightly outward using a 2×4 stake and a level. A 5-degree lean on an 8-foot post means the top of the post is about 8 inches away from plumb before loading. This sounds like a lot when you stand back and look at it, but once the clothesline is strung and a load of wet sheets is hanging from it, the post will be pulled almost perfectly straight. If you install both posts plumb from the start on a long span, they will gradually lean inward over time as the loaded line repeatedly pulls the top of each post toward the center.
02
Set One Post at a Time with Fast-Set — Do Not Mix Both at Once
With Quikrete Fast-Setting Concrete, you set one post, pour the dry mix around it, add water, and have about 20 to 40 minutes before it begins to stiffen. Do not start the second post immediately after the first — use the set time productively. After pouring the water on the first post, walk the string line to the second hole location to confirm the spacing is correct, then prepare the second hole (check depth, remove loose soil from the bottom). When you return to the first post 20 to 25 minutes later, test it by applying hand pressure — if it feels firm, move to the second post. This sequential approach ensures each post has adequate time to stiffen before any load is applied, and avoids the rushed situation of trying to plumb two posts simultaneously while the concrete is setting in both holes at once.
03
Consider Steel T-Posts for Sandy Soil or Temporary Installations
Steel T-posts — the galvanized steel posts used for temporary fencing — are an entirely concrete-free clothesline option for light-duty use in firm to medium soils. T-posts are driven directly into the ground with a post driver (available at farm supply stores for about $30 to $40), take about 5 minutes to install per post, and can be pulled out and relocated at any time. The disadvantages are that T-posts are less rigid than a concrete-set 4×4 wood post and will flex more under a heavy load of wet laundry. In loose sandy soil, T-posts can also lean over time as the soil provides less lateral resistance than concrete. For a permanent clothesline in firm soil where appearance matters, concrete-set wood posts are the right choice. For a seasonal clothesline or a garden area where you want flexibility, T-posts skip the concrete entirely.
How much concrete does a clothesline post need?+
A standard clothesline post in a 10-inch hole at 36-inch depth needs approximately 1.80 cubic feet of concrete per post with the 10% waste factor, or 4 bags of 60 lb concrete. For both posts of a standard clothesline, that is 3.60 cubic feet total or 8 bags of 60 lb. For a short-span (12-foot) clothesline with 8-inch holes at 30-inch depth, the total drops to 5 bags for both posts. Our calculator shows both per-post and 2-post totals for all three bag sizes simultaneously.
How deep should clothesline posts be?+
Clothesline posts should be buried to at least one-third of their total length. For a post with 8 feet above grade, the total post length including the buried section is: buried + 8 ft. Setting buried = 48 inches (4 feet) gives a total of 12 feet, and one-third of 12 feet is 4 feet — so the minimum is met. In practice, most residential clothesline posts are buried 36 to 42 inches for 7-foot above-grade heights, which is slightly below the strict one-third rule but acceptable in firm soil. In freeze-thaw climates (northern US), depth must also reach below the local frost line to prevent frost heaving in winter. Our calculator shows a live one-third depth check for your entered post height.
Can I use Fast-Set concrete for clothesline posts?+
Yes, and for a clothesline post job, Fast-Set 50 lb bags with the dry-pour method is the best choice available. Pour the dry mix into the hole around the plumbed post in 4-inch layers, then slowly pour approximately 1 quart of water per 50-lb bag over the top. Do not stir or rod the mix. The concrete wicks moisture from the surrounding soil and from the water you add, and stiffens in 20 to 40 minutes at temperatures above 45 degrees Fahrenheit. The simplicity — no mixing, no wheelbarrow, no cleanup — makes Fast-Set ideal for a clothesline job where you are setting 2 posts of 4 to 5 bags each.
Should clothesline posts lean outward?+
Yes, for spans of 15 feet and longer. The traditional practice is to install each clothesline post with a 5-degree outward lean — tilted away from the center of the line — so the post corrects to plumb when the line is loaded with wet laundry. The loaded line creates a lateral (outward) force on both posts that tends to pull the tops inward toward the center. By pre-tilting the posts outward by 5 degrees during installation, the laundry load counteracts the lean and the posts end up vertical under load. Posts installed perfectly plumb from the start on a 15 to 20-foot span will gradually lean inward over several seasons as the repeated loading works the post footing in the direction of the force. For very short spans of 12 feet or less, the tension loads are small enough that plumb installation works fine.
Do clothesline posts need concrete?+
Not necessarily. Steel T-posts (the galvanized steel posts used for agricultural fencing) are an entirely concrete-free clothesline solution for light-duty use. T-posts are driven directly into the ground with a post driver and can hold a single clothesline in firm to medium soils without any concrete. They are not as rigid as a concrete-set wood post and will flex more under a heavy load, but they are perfectly adequate for a light residential clothesline in firm soil. If you want a permanent, rigid installation or if your soil is loose or sandy, concrete-set wood posts (4×4 minimum) are the right choice. For a temporary or seasonal clothesline in a firm lawn, T-posts skip the concrete entirely.
What size clothesline post is best?+
For a standard residential clothesline with 1 to 3 lines, 4×4 pressure-treated wood posts (actual 3.5 x 3.5 inches) are the most common and practical choice. They are widely available, easy to cut and drill, and have adequate strength for typical clothesline loads in spans up to 25 feet. For spans over 25 feet or for a multi-line clothesline carrying heavy family washes, 6×6 posts provide more rigidity and lateral strength. Some traditional T-shaped clothesline designs use a 4×4 post with a 2×4 or 2×6 crossbar bolted at the top, which allows 4 to 6 lines on a single post pair. For all in-ground installations, use ground-contact rated pressure-treated lumber (UC4B minimum) to prevent rot in the buried section.
What is the standard clothesline height?+
The standard clothesline height for the line itself is 5.5 to 6.5 feet above ground level — high enough that full-size bedsheets do not drag on the ground, but low enough that an average adult can reach the line comfortably to hang laundry without a step stool. Since most clothesline post designs have the line attached to a crossbar or hook at the top of the post, the post height above grade is typically 7 to 8 feet to position the line at the 5.5 to 6.5-foot range. T-shaped posts with a 24-inch crossbar at the top use a post height of about 6.5 feet above grade so the 4 line attachment points at the ends of the crossbar are at approximately 6.5 feet.
What clothesline span is too long without bracing?+
Spans over 25 feet begin to generate enough lateral tension force on the posts when fully loaded with wet laundry that additional bracing becomes advisable. The two traditional solutions are a diagonal brace wire (a guy wire running from the top of each post down to a ground anchor on the outside of the post, angled at about 45 degrees) and the H-brace (a horizontal 2×4 connecting the two posts near their tops, with a diagonal wire running from one top corner to the opposite bottom corner to form an X pattern that resists the inward lean). Both solutions work well. For spans over 35 feet, adding a center post with a pulley allows the long span to function as two shorter spans, which eliminates the bracing requirement entirely.
How many clothesline posts do I need?+
A standard 2-post clothesline covers spans from about 10 to 30 feet and is the most common residential configuration. For longer total line length, you have two options: add additional lines between the same 2 posts (typically 3 to 6 lines on a T-shaped post design) or add a third center post to extend the total span while keeping each individual section under 20 feet. A 3-post configuration with 2 spans of 15 feet each gives 30 feet of total usable span with better post stability than a single 30-foot span between 2 posts. Our calculator always assumes 2 posts (the standard configuration) but you can run the calculation twice for a 3-post system by calculating one span at a time.
What type of clothesline is best — rope, cable, or plastic line?+
The three most common clothesline materials in the US are twisted cotton rope, vinyl-coated steel cable, and polypropylene plastic cord. Vinyl-coated steel cable is the most durable and holds up best in outdoor conditions — the steel core prevents stretching under load while the vinyl coating protects fabric from snags and rust stains. Cotton rope is the traditional choice and is gentle on fabrics but stretches when wet and can mold or mildew if it stays damp. Polypropylene cord is inexpensive and weather-resistant but tends to develop surface fuzz over time that can leave small fibers on dark fabrics. For a permanent installation, vinyl-coated steel cable in 3/16-inch or 1/4-inch diameter is the best overall choice.
How much weight can a clothesline hold?+
A properly installed clothesline with concrete-set posts should hold a full load of wet laundry without difficulty. A single load of wet laundry (sheets, towels, jeans, shirts) from a standard US washing machine weighs approximately 15 to 25 pounds when wet. A fully loaded 4-line clothesline spanning 18 feet might hold 4 to 6 loads simultaneously, totaling 60 to 150 pounds distributed along the lines. This weight distributes across the line length and is shared by both posts, so each post sees approximately 30 to 75 pounds of downward load. The lateral (outward) force at the top of each post from a loaded line on a 18-foot span with a 1-foot sag is roughly 10 to 20 pounds — well within the capacity of a concrete-set 4×4 wood post in firm soil.
Can I install a clothesline post without digging a hole?+
Yes, using a steel ground anchor (a spiral or screw-type anchor that is screwed into the ground) or a driven steel stake. Ground anchors are available at farm supply stores and home improvement centers in versions rated for various soil types. The limitations are that ground anchors provide less lateral resistance than a concrete-set post in most soils, especially clay or sandy soils. Spiral ground anchors also cannot be installed in rocky or root-dense soil. For a light-duty clothesline in a firm lawn soil, a 36-inch spiral ground anchor driven at a 45-degree angle can work adequately. For a permanent installation with a full laundry load capacity, a hole and concrete footing is the more reliable choice.
What is the best concrete for clothesline posts?+
Quikrete Fast-Setting Concrete in 50 lb bags is the best concrete for clothesline posts because the dry-pour method (no mixing) makes the job fast and easy for one person. The concrete sets firm in 20 to 40 minutes and reaches working strength in 4 hours. For standard wet-mix installation, Quikrete 5000 in 60 lb bags (5,000 psi) is a good choice for better freeze-thaw resistance in northern climates. Avoid using standard 2,500 or 3,000 psi general-purpose concrete mixes in freeze-thaw climates — the lower strength concrete is more susceptible to surface spalling around the post after repeated freeze-thaw cycles, which can compromise the post anchorage over time.
Do clothesline posts need to be pressure treated?+
Yes, absolutely. Any wood post set in concrete in direct ground contact must be pressure treated to at least UC4B (Use Category 4B, ground contact general use) to resist rot and insect damage. Standard construction lumber (spruce, pine, fir — SPF) without pressure treatment will begin to rot at the soil-to-concrete interface within 3 to 5 years in most US climates. UC4A rated lumber (the common residential fence post rating) is also acceptable but has lower preservative retention than UC4B. The pressure treatment does not affect the appearance of the above-grade portion of the post — it will look the same as untreated lumber when painted or stained. Never use wood that is simply painted or stained (rather than pressure impregnated with preservative) as a substitute for pressure treatment in in-ground applications.
How do I string a clothesline between two posts?+
After the posts are set in concrete and the concrete has cured for at least 24 hours, string the clothesline using a turnbuckle system for best long-term performance. A turnbuckle (a threaded tensioning device) is attached to one end of each line and allows you to tighten the line after installation and periodically over time as the line stretches. Thread one end of the clothesline through a screw eye or hook at the top of one post, run it to the opposite post, and thread it through a turnbuckle attached to a screw eye on the second post. Tighten the turnbuckle until the line has about 2 to 3 inches of sag at center with no load. The line will sag further when loaded with laundry — the goal is 12 to 18 inches of center sag under a full load, which keeps the laundry clear of the ground while preventing excessive tension on the posts.
How long should I wait before using the clothesline after pouring concrete?+
With Quikrete Fast-Setting Concrete, wait 4 hours before attaching the clothesline hardware and 24 hours before hanging any laundry. The 4-hour mark is when the concrete reaches approximately 50% of its design strength, which is adequate for the post to hold its position under light load. The 24-hour mark is when the concrete is strong enough to handle a full load of wet laundry without risk of the post shifting. With standard 60 lb or 80 lb concrete mixed normally, wait at least 24 hours before attaching hardware and 48 to 72 hours before hanging laundry. Full design strength at 28 days — but the practical working strength is reached within the first 3 to 7 days for this application.