Thread: load calculations for wood joist=my brain hurts!!!

ahhhhhhhhh! my brain is seriously about to explode!!!!
(searched and searched and searched and found nothing pertinent btw)

here's the situation, hopefully someone can offer some good advice.
In the process of setting a J head in the shop and trying to determine how much support i need under the floor.
It is a pre war building, 38" crawlspace, full 2" x 12" joist that are tripled up and 12" OC with an 11' span.
Crawled around under the building yesterday to get a close look, girders and bearing wall's look good and surprisingly not sagging too much considering the buildings vintage.
My initial plan was to pour a solid concrete pad all the way down to the ground but there are major concerns with this idea as im not 100% sure that the machine will work in the configuration that i have drawn (very tight shop) and at 30 bags of crete that's a lot of work to have to redo immediately and a lot of money that i don't have down the drain, that would suck.
A contractor friend came by last night and was saying that my dead load rating exceeds the weight of the machines and worst case the floor would sag but he is one of those guys that likes to hear himself talk, if you know what i mean
That said i was considering an 8" block bearing wall immediately under the joists that will carry the J head and setting the Van Norman 1/2 over the next available already existing bearing wall/girder near another wall.
Obviously coming into the shop one morning to find a J head sitting on the dirt ground and a pile of broken wood joists would be pretty catastrophic.
And here i thought these old wood floors were going to be enjoyable .
Best scenario would be build a wall under the joists where the J head will live and that way moving it around later will be an option.
Really really trying to avoid pouring the almost cubic yard of concrete one wheelbarrow at a time, 70' into a 38" crawlspace by hand just to find out that the machine wont work where the pour was done.
I should mention that i rent the building and have no interest in major structural changes and can not afford the $ or time it would take to pour a large enough pad that machines could be moved around at a later date.
another possibility would be set the J head down for now and leave the VN in the shed. Make sure the machine will be located in a good useable spot, maybe use it for a few weeks to verify good location then move them just for long enough to pour a footer under them. Again, i just really don't want to have to do it twice.
so anyone ever been in a similar situation?

My armchair engineering says with an 11' span, I would place a 8" wideflange
beam down there about 12' long, on 3 piers (8" carboard tubes filled with cement)
to shorten span to 5 1/2' and this would give you a large (approx. 11' x 12')
area that's suitably re-inforced for both toys.

3 little piers could easily be hand dug. The beam slid in thru a hole on the sidewall.

Wedge as needed to get the beam loaded.

Doug, had not considered caisson tubes, thats a great idea. I actually have a pile of huge 6" x 12" heart pine girders that i could use as the 'beam' as well.
this may be the easiest way to go.

The J head only weighs a ton and a half. That's npt real heavy bt it does represent a concentrated load.

How about this work-around. Forget about the slab and elaborate concrete work. . Support the floor for the subsoil. Determine a location that avoids the joists. Drill 1/8 holes in the centered where the machine base actually contacts the floor. Drop broom straws, string, wire, whatever for "finder things" through the holes and stop them from falling through with masking tape flags.

Slither into the crawl space with four concrete flagstones from the home canter. Bed them level into un-disturbed dirt centered under the finder things. Cut 6" x 6" wood posts a little short. Place thme centered under the finder etc. Shim and wedge with opposing shingles to tighly contact the floor. Now you have the floor rigidly supported. You can load the floor with the machine in that spot only witout fear of sag. The support goes all the way to the undisturbed soil. Roll the machine across the floow on 3/4 ply grillage to distribute the weight a little. Then you can slide it off the ply onto the installation site.

I would use a 4mm spreader plate on the top to make sure the machines weight was spread across several joists (in case its got feet). The I would go underneath and scrape away some dirt under where the machine will sit, under the joists, put down a thick plastic bag/some damp course stuff, then a high density 18" X 9" X 4" concrete block laying down flat. Then cut a leg out of 4" X 4" timber to jamb under the joist on to the block. Blob of glue on the block, nails toshed in to hold the top of the leg in place, use at 4' centres on all joists around the machines location. You could jack the joists up by 1/16" before fitting the legs just to make sure its tight.
Frank

I would suggest a "strong back" hung under the joists with threaded rod to distribute point loads, to pull down the occasional high spots, etc. but that would most likely require a subfloor under the flooring.

Counterbore the flooring, install bearing washers and nuts.....

I have cured irregular ceiling joists and noisy floors with this method. In my case, I used timber (lag) screws directly into the joists.

i am just about 100% sure that the collective brainpower on this site rivals that of the entire interwebs combined, and this is why i spend entirely too much time on here

the reason why i initially dismissed any sort of wood beams as support was the amount of dampening that a solid concrete pad would allow, i assumed that a wood built support system would allow the machine to bounce around too much. That said Forrest, i think a hybrid of your and Doug's idea will suit this application just fine...and i do have these huge heart pine beams just sitting here taking up space
thanks so much for the quick and logical replies gents.

edit: damn you guys are fast! 2 more replies as i was replying to Forrest and Doug. All great ideas...thank you guys so much

Lets make sure I'm understanding you correctly. You have full 2 x 12, tripled up, on 12" centers. To me, that makes the floor 50% beam. Correct? If so, a standard Bridgeport base will cover two beams.

Without digging out tables (since you didn't identify the species anyway), I would say you are in good shape as is. I might have some concern as far as X bracing to keep the beams from rolling over, but 6" wide and 11' span should still be ok.

One of the wonderful things about wood as an engineering material is its flexibility. I suspect you will get very nervous about the sag in the floor long before you are in danger of breaking the beams. I would place the mill in the desired position and see what you think about it. Move it as necessary. When you like the final position, then support the floor.

I have done a similar support on a house. I made a 2' x 2' steel ground bearing plate. I bought a pole type floor support jack to get the adjusting screw and nut. I made a steel spreader plate for the wooden beam. I used about a 3/4" centerdrill and made a center mark in both the spreader plate and adjusting screw. I put a 1/2" bearing ball in the center marks to act as a bearing between the spreader plate and the adjusting screw. Tighten as necessary. Cover the screw threads and the bearing ball liberally in grease to prevent rusting, as it may be several years before you need to adjust it again.

Handy dandy info:

WWF: Wood Strength

Note moment of elasticity on the good Doug Fir shown is less than 1/15 of steel. Not very stiff stuff.

I'm with gbent - unless its a typo you already have enough floor for the Bridgeport.

If you really want it more solid I'd scrape a flat spot under the machine's resting spot, build a form of 2x8 lumber to sit on the undisturbed flattened soil and two stud walls that sit on top of the form and extend to the floor joists. After everything is all nailed/bolted together, pour the form full of concrete and go away. If you built this out of pressure treated lumber you simply leave the form in place and go back to machining, never looking under there again.

Or the super easy way is several cap blocks on undisturbed soil and some screw jack posts going to the joists. This is adjustable, which might not be a bad idea but undisturbed soil under a building that's been there for a long time with no water problems is damned stable.

Edit: What is pre-war? Do you mean WW2, WW1 or the War of Northern Aggression?

Have you thought about hiring an architect or engineer?Might save you money in the long run.
I was a building contractor for 30 some years and I would not bid on your job until I got expert advice.
mike

I did a little additional support for a friend a while back that was nothing more than a mud sill and some cheap scissor jacks bought at the local auto salvage for 5 bucks apiece. 4 jacks 20 bucks and move them at will. Plus you can take them when you leave.

+1 on Gbent's suggestions

"full 2" x 12" joist that are tripled up and 12" OC with an 11' span," is a ferocious joisting schedule! Was the building originally built to store Steinway Concert Grand harps*? (*the great iron casting that all the strings of a piano are tensioned over.)

100 years ago and more, it was common to build manufacturing facilities several stories high, with machine tools near the top on wooden floors. The machined parts then trickled down through proccess to finished product and out the ground floor door and commonly some of the machines out-weighed that dainty Bridgeport, while sometimes the floor beneath the machines supported thousands of pounds of line shafting and cast iron pulleys with many leather belts tensioning it downward to second op machines below.

Providing that the structure is sound, I wouldn't even crack a structural table, just move it in.

String over the floor from support girder to support girder, right in front of where you intend to set the mill and fit a little wood gage, X marks the spot. Move in the Bridgeport, restring and if there is over an 1/8" of daylight over the gage, I'll come over and help you shore it. Rest assured that it would take far more than an 1/8" deflection to seriously stress that construct. I'd use a bit oversized 3/4", (actually, I'd use 1/2") steel plate to spread concentrated leveling points and no, those little Bridgy leveling screws will not bend down ear's on that 3/4" plate.

Licenced General Contractor since 1972, (now retired, license on inactive status) and quite impressed with your floor.

Bob
PS, we'll use some of the great techniques above if I'm wrong.

One of my later projects, (winding down as General Superintendent) over 200,000 sq. ft. in 7 buildings, (2 more of them visable in large opening on right) of this:

Didn't even wince as the crane lowered the large HVAC units onto those flimsy bar joists.

I assume by a J head, you mean a J head milling machine.

Whenever you are installing something that you think *might* stress the building, it is a good idea to forget about shoring up the building and focus just on the item. In other words you are much better off making a footing for the machine rather than messing with the flooring.

One of the reasons for this is that no matter how good you make the floor you will have sag and compression and the machine will not stay level. Also, the floor will vibrate. Seriously, do you want the machine bouncing up and down a few tenths as it is operating? Probably not.

Cut hole in floor. Dig a 4'x4'x12" hole in the ground. Prepare 5 lolly columns to the height from ground to the base of the machine plus 12", so I guess that would be 5x 50" lolly columns. Position the lolly columns like the dots on a 5-spot dice, then pour the 4' x 4' foundation around the columns. At the top of the columns build a form and pour a 3" pad on top the columns. The machine sits on this pad. The image shows the elevated footing:

Originally Posted by Robert Campbell Jr.

"full 2" x 12" joist that are tripled up and 12" OC with an 11' span," is a ferocious joisting schedule! Was the building originally built to store Steinway Concert Grand harps*? (*the great iron casting that all the strings of a piano are tensioned over.)

100 years ago and more, it was common to build manufacturing facilities several stories high, with machine tools near the top on wooden floors. The machined parts then trickled down through proccess to finished product and out the ground floor door and commonly some of the machines out-weighed that dainty Bridgeport, while sometimes the floor beneath the machines supported thousands of pounds of line shafting and cast iron pulleys with many leather belts tensioning it downward to second op machines below.

Providing that the structure is sound, I wouldn't even crack a structural table, just move it in.

String over the floor from support girder to support girder, right in front of where you intend to set the mill and fit a little wood gage, X marks the spot. Move in the Bridgeport, restring and if there is over an 1/8" of daylight over the gage, I'll come over and help you shore it. Rest assured that it would take far more than an 1/8" deflection to seriously stress that construct. I'd use a bit oversized 3/4", (actually, I'd use 1/2") steel plate to spread concentrated leveling points and no, those little Bridgy leveling screws will not bend down ear's on that 3/4" plate.

Licenced General Contractor since 1972, (now retired, license on inactive status) and quite impressed with your floor.

Bob
PS, we'll use some of the great techniques above if I'm wrong.

i love everything about this post Bob, you guys have all really calmed my nerves on this deal and for that i thank you, beers on me next time im in SoCal buddy!
My brother and another helper are coming tonight to help, my revised and much less stressful plan is to use the heart pine beams that i have to build 2 bearing walls immediately under where the VN and J head will live. I went to home depot earlier and bought 20 or so of each 6" lags & 6" timberloks plus a small pile of simpson corner ties to fasten everything together and to the existing structure. Plan is to make it to where it cant rack and i think well be more than fine.
thanks again everyone, for real...i will take a few pics of our work tonight and post up later.

Im sorry I cant give you any real numbers as a enginer could but as a carpenter I can tell you your framing is way more than enough. one thing i havent read yet is what is the actual floor made out of Ill take a guess that its oak togue and groov maybe 5/4. I wouldnt be scared to park the forklift next to your mill. One other thing to think about is that this is probily biult with real wood virgin old groth very tight grain and extra heavy not like todays woods big open grain real soft regown in 50 years.

One other thing i can tell you is when I was in high school I worked in a sporting good store and in the back rooms ther was an upstairs and up ther is were they stored all the free weights and gym sets ya no comn sence at this store but ther would be thousands of pounds of weight stacked in a small area and that was biult with modern 2x10 16" on center 12' span and ever 4' was doubled with 3/4 plywood tg. never any problems.

Originally Posted by Robert Campbell Jr.

"full 2" x 12" joist that are tripled up and 12" OC with an 11' span," is a ferocious joisting schedule! Was the building originally built to store Steinway Concert Grand harps*?

Consider putting a older upright piano in a typical home. Under my living room floor I have planed 2 x 10 (actual dimension more like 1 5/8 x 9 5/8) on 16" centers spanning 12.5'. Didn't think twice about putting a hundred year old upright piano in the living room. Now a bridgeport is maybe three times the weight of the piano but you have considerably more then three times the support. You have more then triple the thickness with your triple joist measuring a true 6" on 4" narrower centers , as well as the increased depth of section from 9 5/8" to 12" and a shorter span.
Put the bridgeport in and it will be fine. If you want to measure the deflection you can but I would be surprised if you felt that you still needed added support. As others have said a simple jack post set on a spreader pad on the undisturbed soil wold be more the adaquet

well i will mention again that while i do think that in theory this floor would have held the mills i was attempting to minimize vibration in the floor transferring up through the machines. Im sure i was over thinking the entire process but like many of us here i don't mind a little 'overkill' in the shop.
that said i got it sorted out last night, my brother and one of his friends came and we worked till 10 getting it wrapped up.
Decided not to use my beautiful heart pine beams and opted to use some old treated pine and some large chunks of 3 x cypress that i had in the lumber pile.
We removed the loose top soil, packed down the ground and built 2 walls. The rear wall (against sill) is 2 pieces of cypress with 2 x 6 framing in between, the foremost wall and the one that will really carry the weight was built with some crazy dense treated 6 x 8 lumber with 3" x 10" cypress 'studs'. Both walls were tied into existing framing with simpson corner gussets and some hurricane strapping then both walls were tied together with a few horizontal 2 x 6 legs.
i think it will work..i hope
thanks again for all the good advice guys


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"i think it will work..i hope
thanks again for all the good advice guys"

Thanks for what?
Most people posted that they though what you had existing seemed more than adequate,
and yet you continued on your own path and shored up the floor.
So you are thanking the group for their advice you did not follow?
I suppose you re enforced the floor just to make yourself feel good (nothing wrong with that, of course).
Not sure if you were actually attempting to seek peer approval here to gain an additional avenue to make yourself feel good, but I would say peer approval in the majority might not have been what you received.

--Doozer