Hay bale

Can anybody please advise me the size and weight of a standard rectangular type hay bale. I am trying to figure hay mow loading with a full loft.

Regards

Ken Hume

[This message has been edited by K F Hume (edited 07-26-2001).]

I believe it's 40 lbs per bale. But others will probably have more answers. Good luck, Jim

According to ASCE 7-98, Minimum Design Loads for Buildings and Other Structures, the minimum live load for hay and grain storage is 300 lb/sq ft (14.4 kN/sq m). This doesn't answer your question regarding the density of a hay bale, but it might be a start.

Dear Dick,

You have actually answered the question that I was getting around to asking but in an indirect sort of way. The magnitude of the code loading takes me by surprise. I wonder if it is realistic to apply such a heavy loading across the entire hay mow floor given that it will carry full height loading only over the central section and less towards the eaves due to the sloping roof ?

Regards

Ken Hume

Ken,

The load is quite high, probably because no one knows a priori the geometry of the structure that will support the load or the exact nature of the load. If you know the density of the hay, then you can account for the limited headroom along the sides and possibly reduce the load. The load standard has a footnote that might tickle you: "Use weight of actual ... stored material when greater." Yea, no kidding! Basically, I think that you are back to weighing and measuring a bale. You might want to soak it with water first!

Dick

Dear Dick,

I used your 300 lbs / sq ft figure today in my model and got really alarming results - 20" deep beams.

I then did a quick check assuming that a hay bale is 2 x 2 x 4 and weighs 50 lbs and I got a remarkably good comparison with your code figure loadings.

This led me to question why the typical 8 x 8 scantlings is so common in North American mid west barn frames.

The answer might be simple. I guess that the hay bale is probably a fairly recent invention and I would surmise that most barns were built to be loaded from the ground floor to the roof and did not necessarily have a fixed mow floor. I have seen many pictures of round poles which are simply laid across the mow beams and this might explain how the old barns did not need to be built to such a demanding standard since most of the weight must have been bearing on the ground floor and of course there would also have been an internal wall pressure as well.

I managed to solve my problem using cleverly positioned bracing and also narrowing the main mow beam span which helped reduce horizontal shear from 120 to 60 psi and also depth of beam from 20" to 12".

Now I know why those Dutch barns have such deep swing beams. It does not appear to be overdesign.

I will weigh a hay bale tomorrow at my friends farm.

Does anybody have any thoughts on these observations.

Regards

Ken Hume

Hey Ken and Dick

I've tried to check hay density figures and have found that results will vary. The heaviest per cubic foot bale offered for sale was a high grade alfalfa bale 15" x 18" x 36" weighing 80 lbs. That is 14.2 lbs. per cubic foot. Hay, as a commodity, is sold by the ton and to grade standards. Farmers engaged in the sell of hay as a commodity should know the bale weight. Lacking input from a supplying farmer, a local farmers co-op should be able to give a good idea concerning your local market. Grain density is much greater, wheat berries weigh about 48 lbs/cubic ft.

The 1842 Penn. style barn I am currently working has floor joist hewn on opposite sides 8 inches deep with a min 10" width on average 36" centers spanning 9' to 10'. Longitudinal beams are 10 x 12 with posts every 10 feet.

The standard of 300 psf min. turns up in a 1958 handbook.

Sorry, bale size I stated is correct the weight should be 70 lbs or 12.4 lbs/cubic ft.

Although I do not consider myself an expert, I have 12 years experience as a structural engineer and 6 years experience designing and building timber framed barns. Based on my experience, I feel a reasonable number to use for typical timber framed hay loft designs is around 60psf. Here is why. Our typical barn is a 24x36 bldg (864 sqft of loft) with a 4ft-knee wall. This building can accommodate approximately 500 bales of hay, which equals 0.58bales per sqft. Or, at 50# per bale, around 30psf. I like to design lofts for around 60psf, but I'm not uncomfortable with 50 or even 40 psf. A building with more overhead or large haymow would require a similar evaluation. In order for a 24x36 building to approach 300psf of loading, it would have to hold 5,184 bales of hay. That's a lot of hay. 300 psf seems excessive for all put the largest commercial hay storage facility. Any thoughts?

From what I've read in the last day or so about hay density, it seems that 14 pcf might be a bit high. But let's assume that is a reasonable number. If the stack could be limited to a 4 ft. knee wall height, then a number like 60 psf is appropriate. However, I would not feel comfortable with that value. Hay stacks routinely reach 8-10 ft in height. 300 psf would require a 20 ft stack -- seems a bit unreasonable. Nevertheless, I would be inclined to design for a relatively full loft, assuming that the farmer has mechanical means to fill it.

Interesting question! Thanks Ken. I'll pose it to my structural analysis class next semester and see what they do with it.

I agree with Dick's assessment that a full loft should be assumed. In the case of a 24x36 barn, 500 bales are packed almost to the rafters. Although I'm certain someone could get 600 bales in that same size loft, you couldn't get many more.

Another thought is the economy of designing a building using timber framing to carry 300psf. I enjoy timber framing, but that would be one big, heavy and expensive building. Most people would have trouble justifying the expense of a 300psf timber framed structure. I know I would!

A couple of additional thoughts. For me, 14.2pcf seems quite high for hay. That would imply that a 2'x2'x4' bale weighs 227lbs. Every year we load our loft by throwing 500 bales over our heads. I believe a lightweight bale to be 25lbs and a heavy weight bale to be 40lbs. At even 50lbs per bale that's 3.1pcf. The day I run across a 200+lbs bale of hay is the day I stop moving hay!
The few Pennsylvania Dutch barns I have seen appeared to be more heavily framed then the typical New England barn. The vast majority of older New England barns are lightly framed by today's standards. Some of those barns have quite large haymows that could support over 20' of hay and have served as working barns for up to 200 yrs. I would not be comfortable using older barns as a basis for today's design load criteria, but I am comfortable to use them as a conformation.

I see that we are far apart on what bales weigh or can weigh. Equipment, crops and conditions vary. Grandpa's baler is on it's last legs and will be replaced. John Deere offers a large square baler that produces 31.5" x 31.5" x 96" bales to a max. weight of 1,000 lbs. Over 18 pcf. That particular size is designed to fit a truck trailer, dense, stackable and stable in transit, this is a commodity bale. Small bales are also sold in the commodity market but are less desirable due to increased handling, high density bales are required for small bales to have a place in the greater market.

Suppose I want to build a theater with a balcony. The balcony will only be open for the kiddie matinee and no over 65 lbs. will be allowed, so I claim. So let's build to a lesser standard. No one should trust me to keep the public safe in the future. The kiddie theatre failed and new ownership thinks big people buy more tickets. Our building standards should and do guide us towards the future.

When the old balers get replaced density goes up.

I called a Minnesota marketer of alfalfa hay today and asked how heavy are your bales? 3' x 4' x 8' bales vary from 1000 to 1300 lbs.

Please check this out for yourself.

Yesterday while delivering lumber to a horse barn, I asked the owner how big his barn was and how many bales of hay could he store. His barn was 30'x 30' and he had currently 300 bales and was intending to add 150 more. We discussed this pound per square foot issue and he figured quickly in his head that he was placing between 60 to 80 psf on his hayloft. He figured his bays weighted about 40 lbs each, as they were string tied. He stated, as mentioned, hay bales can weigh a lot more, especially went they are wire tied.
Just some info for you, Ken.
To Dick Schmidt: let us know what your class comes up with, next semester.
Good luck, Jim

Hey Guys !

This reply makes this subject joint equal for most replies. Who could have thought that hay was so interesting !

I checked with my horse farmer friend today and he measured some English hay bales made recently from simple meadow grass and we got an answer as follows :-

dimensions 21" x 16" x 39"
weight - 35 to 50 lbs

This gives a foot print pressure of 4.6 - 6.6 lbs per sq ft.

The heavier bales were on top of the pile in the field and had been exposed to some light rain. The lighter bales were protected inside the stack in the field so Dick's comments re water seem to hold true infact water has made the bales 45% heavier but still lighter than alfalfa.

Regards

Ken Hume

Even though I've thrown (and inhaled) more bales of hay than I care to remember, I haven't the foggiest what one weighs...

I'm responding only to see (finally) an A the E thread catch on fire.

Burn it up.

About what period in time did it become common to bale hay etc ? Loose stored hay would be a much lighter load (psf) than baled material.

I believe the fist baler was patended in 1879 changeing barns in their use and construction almost overnight, just as the move towards round bale is now effecting agriculture and it's associated outbuildings currently.

Here is a link to baler, binder and twine. http://www.bridoncordage.com/frmain01.htm

I came up against the same question a few years ago. The published numbers for the weight of baled hay in engineering references are ridiculous at 20pcf. Dry pine is 26 pcf. Those are some balers! I weighed some bales and came up with 5 to 7 pcf. I ended up designing the mow floor for 100 psf, mostly for the tractors and haywagons. We were using recycled timbers hewn on the top side only. We selected the largest ones for use in the two bays with the doors. I also rationalized that as the floor deflects, the hay over the posts does not. If the bales are laid-up in a running bond as in masonry, the posts could theoretically support an inverted pyramid of hay. It could be argued that the weight of of the hay on the joists might not exceed that of a pyramid of hay whoose base is the size of the bay. A similar concept in 2 dimensions is used in designing masonry lintels. Hay is structural in another sense: How many barns have you seen that probably wouldn't survive a winter unless they were stuffed to the gills with hay to prevent them from blowing over? I pass a few like that every day (and few that are empty that should be shored with hay.)
Good luck,
Chris

Dear Chris,

Thanks for your lateral thinking observations re the hay bale floorloading quandry. The barn I was designing was the replacement for the burnt down barn at Northfield Mount Hermon School, Mass.

I managed to get around the problem of overloading of the mow floor by inserting a loft floor as well. This physical barier limits the static head pressure which can be exerted by the hay on both the mow and loft floor joists. I have come to the conclusion that hay bales are better stacked on the ground up through an open barn structure as was the original practice and yes this would help with stablising an old barn.

Regards

Ken Hume