Where hay tarps actually fail
What should you measure before choosing a hay tarp?
Measure the stack you will cover. For round bales, record the actual diameter, the arrangement of rows and the stack length. For square bales or an irregular pile, send a labeled profile instead of selecting a round-bale pyramid by guesswork. The distance over the stack's surface differs from its ground footprint.
The round bale stack calculator models a tight pyramid of equal, circular bales. It shows a geometric span alongside dated vendor charts. Flattened bales, gaps and settlement change that surface, so record the measured span too. A result that is close to a nominal tarp width leaves an unresolved question about the finished cover, not an automatic fit.
| Request field | What to record | Why it matters |
|---|---|---|
| Stack profile | Bale type, actual dimensions and row arrangement. | It defines the surface the cover follows. |
| Surface span | Measured distance over the stack to the intended cover edges. | A footprint width is not a cover width. |
| Length and ends | Stack length and the intended coverage at both ends. | End allowances differ between vendor guides. |
| Finished size | The usable cover dimensions after hemming, and the agreed tolerance. | A listed cut size may shrink through fabrication. |
| Repeated stacks | Quantity and a separate sketch for each differing profile. | One cover specification may not fit every pile. |
N2 example of differing sizing instructions: Mytee Products' hay size selector, read October 3, 2026, asks for actual bale measurements and specifies its own end allowance. Its guide is not the allowance used by every cover system. The calculator retains its separately sourced rule and identifies it in the result.
Which storage conditions belong in the request?
State the expected storage period, base and drainage condition, exposed edges, intended ventilation and existing cover system. Include the cover maker's installation instructions if you are replacing a known system. Ask how the proposed hem and fixing arrangement works with that system; do not substitute a universal tension recipe.
Oklahoma State's Round Bale Hay Storage explains that moisture, climate, storage duration and the site affect losses. It also cautions against sealing high-moisture hay under plastic and against tying the cover tight in the covering method it describes. That is why a grower's retensioning account below cannot be generalized to every cover assembly.
This worksheet prepares a cover specification. It does not decide whether hay is ready for storage or design a wind-resistant installation. Those questions need the applicable cover instructions and local agricultural or site advice. For the storage comparison, see what covering hay is worth. Keep any expected loss reduction separate from a product promise.
The sequence, in a grower's words
A few inches of slack work loose in a windstorm and take 15 to 30 minutes to reach violent flapping, which ruins the waterproofing at best and normally starts tearing the tie-downs out, with the stack open before anyone notices it was loose.
N3 · grower post, Hay & Forage Forum, 2018-12-02
In this account, the grower connects a settling stack, slack, movement and damage at the fixing points. It is a useful description of an observed failure, not a controlled test of why every cover fails. The request should identify the hem, fixing system and installation instructions rather than infer them from thickness.
This is also why service life claims are hard to compare. A cover that lasted seven years on one farm and four months on another may be the same product, tensioned differently, on stacks of different heights, in different wind exposure.
The buyer already suspects it, and nobody confirms
- Two named brands held up well over 7 or 8 years, one a little better than the other and more expensive; recycled billboard covers from the same poster shredded within a year in snow country. (N3 · grower post, Hay & Forage Forum, 2020-07-05)
- A buyer asking which cover to choose writes that he assumes the difference is the tie-down points and the stress management. Nobody in the thread confirms or corrects it. (N3 · buyer post, Hay & Forage Forum, 2020-07-05)
- Growers using billboard covers thread a PVC pipe through the hem loop and tie off there, because there are no grommets and the string tears out. That workaround is the sleeved-pipe feature a purpose-built system sells. (N3 · grower post, Hay & Forage Forum, 2018-12-04)
- The thread is still live in 2024: one poster says he would rather spend more once than replace cheap covers twice in a season. (N3 · grower post, Hay & Forage Forum, 2024-05-14)
- Across two additional threads, growers repeatedly separate the cover from the storage system: a peaked stack sheds water, open ends or an air gap let moisture escape, and a drained or elevated base limits bottom spoilage. (N3 · multiple grower posts, Hay & Forage Forum, 2013-10 and 2020-02)
- The same reports identify two installation details worth writing into the plan: protect the sheet from sharp wagon or stack edges, and retension after the stack settles rather than treating first-day tension as permanent. (N3 · multiple grower posts, Hay & Forage Forum, 2013-10 and 2020-02)
The second of those is worth sitting with. A buyer choosing a cover writes that he assumes the difference between a cheap tarp and a purpose-built one is the tie-down points and the stress management. He is reasoning correctly from first principles, and no vendor page he could reach would tell him whether he is right.
The third is the same insight arriving from the other direction. Growers using recycled billboard covers thread a pipe through the hem loop and tie off there, because the string tears out otherwise. That workaround is, feature for feature, what a purpose-built system sells as a sleeved pipe. The market and its cheapest substitute agree on what matters. Only the product pages are quiet about it.
The cover is only one part of the storage system
Two further archived discussions add the conditions around the fixing. Growers repeatedly describe a peaked stack that sheds water, open ends or an air gap that lets moisture escape, and a drained or elevated base that limits moisture reaching the bottom row. They also flag sharp edges as abrasion points and stack settlement as a reason to retension the cover.
These are practitioner observations, not universal design values. They do change what a useful quote should ask. A supplier needs the stack profile, base and drainage condition, intended ventilation, exposed edges and maintenance instructions, not just length, width and fabric weight. Leaving those fields blank pushes the most important decisions onto installation day.
What the vendors publish about the fixing
| Vendor line | Grommets | Hem and fixing |
|---|---|---|
| Tarp Supply | solid brass, about every 24 inches | heat sealed seams, rope reinforced hems, corner reinforcement |
| TarpsPlus | aluminium, about every 18 inches | 1/4 inch rope encased in the hem, triangular corner reinforcement |
| Tarps Now | number 2 brass spur, every 36 inches | polypropylene webbing in the hems, webbing handles around the perimeter |
| A1 Tarps | not published | sleeved PVC pipes along the length, UV-stable rope, patented tie-down system |
Published listings, read 2026-08-20. Named without links: direct competitors.
Eighteen inches, twenty-four inches, thirty-six inches. Between the tightest and the loosest, the number of fixing points on the same edge differs by a factor of two, and not one of these listings says what that changes. The prices do not order themselves by it either: see the specs and prices comparison.
So what do you write on the order?
Everything above turns into a short list of things to state rather than assume. None of it is exotic; all of it is countable at reception, which is the point.
- Thickness measured, and weight per area on a cutting. The two specs do not agree across vendors, so a label is not a measurement.
- Grommet count and spacing against the order. Published spacings run from 18 to 36 inches, a factor of two on the spec that carries the wind load.
- Hem construction opened and checked. Rope in the hem, webbing, or a sleeve for a pipe are three different products sold under the same words.
- Grommet pull test at a corner. Growers describe tie-downs tearing out before the fabric gives, with the stack open before anyone notices.
- Flat dimensions measured against the stack you actually build. A cover sized to the stack footprint and not to the stack plus its overhang cannot be tensioned.
Fixing before fabric: a hem that carries the load, hardware set into that hem, and a tie-down plan for a stack that settles. A thicker fabric on a weaker hem is the more expensive way to fail.
What this guide does not claim
- The failure sequence above comes from practitioner threads, dated and read in full. It establishes a mechanism and a vocabulary. It is not a test result, and no number on this page comes from it.
- None of the vendor sheets compared here publishes tensile or tear values, so nothing here ranks fabrics by strength. That value has to be demanded at contract and tested.
- Wind loading on a covered stack is site engineering. We specify the cover and what holds it; we do not certify that any assembly will hold in a given wind.
Questions
What actually makes a hay tarp fail?
The practitioner accounts on this page describe covers working loose, flapping and failing at fixing points before the center fabric wears through. They identify one failure mechanism, not a universal sequence or a wind rating. Cover design, installation instructions and storage conditions still have to be assessed for each stack.
Is a thicker hay tarp a better hay tarp?
Thickness alone cannot rank different fabrics or fixing systems by durability. In the dated market comparison on this site, thicker listings were cheaper on the five shared sizes. Ask for the proposed material, weight per area, construction and test evidence rather than treating thickness or price as a service-life guarantee.
How far apart should the grommets be?
Three US lines publish 18, 24 and 36 inch spacing, a factor of two, and none of them publishes a reason. Until a vendor states one, the honest answer is that spacing is a decision you have to make explicitly and write down, not one you can read off a product name.
Are recycled billboard covers a real option?
They are a real option with a named trade-off. Growers describe them as cheap and tougher than a hardware-store tarp, but with no grommets, so the ones who use them thread a pipe through the hem loop and tie off there. In snow country the same threads report them shredded within a year.
Practitioner sources read in full on the dates shown: Hay & Forage Forum: what kind of tarps are best for hay? (2020-07 to 2024-05, read in full 2026-08-20); Hay & Forage Forum: what's the scoop on hay tarps? (2018-12 to 2019-02, read in full 2026-08-20); Hay & Forage Forum: hay tarps (2020-02, read in full from archived PDF 2026-08-21); Hay & Forage Forum: storing hay under a tarp (2013-10 to 2013-11, read in full from archived PDF 2026-08-21).
Next: what covering hay is worth, and the family page, hay tarps specified where they actually fail.
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