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