Supporting tools under a P&B floor

[Larry Browning]

As most of you know, I am in the process of rearranging my shop. I have a pier and beam foundation with the heavy TS and jointer sitting right on top of the center beam. The new layout calls for me to move the TS to be just slightly off the center beam, and the jointer to be about half way between the wall and the center beam. I am thinking that the TS will be ok, but I am worried about the jointer. The specs say it has a shipping weight of 421lbs (I think) so I figure it weighs arround 400lbs without the packaging. the floor joists are 2X8 on 16" centers. Do you think I should add some support under the jointer and TS? If so, how should I go about it?

Thanks,

[lou sansone]

what is the span?

lou

[Jeff Sudmeier]

Also, how is the base of the jointer set up? Does it rest totally on the floor for even weight distribution or does it have wheels? If it has wheels, there would only be 4 points of contact and I may be concerned about the flooring holding. If it sits directly on the floor, I wouldn't worry as long as the joist span is proper.

[Jim Becker]

Additionally...how thick is your floor? Two layers??

[Larry Browning]

I knew there would be other information I needed to supply, I just didn't know what it was.
Span is 15ft to center beam, Jointer and TS are not on wheels, 1 layer of 3/4 T&G plywood.

[Joseph N. Myers]

Larry,

Not sure exactly where I got the following information but there is reference to "your nearest Extension Service office" and "How To Build Small Barns and Outbuildings". And I would assume your local zoning board, builders, etc., would have all sorts of correct information.

"Normally, floors are built to carry a "live load" of 40 pounds per square foot. For heavy equipment, this should be increased."

"Live" loads are usually defined as those not associated with the building or its framing; for example, hay, wind, snow and people. "Dead" loads include the building framing and inherent material weight."

To carry the live load of 40 lbs and additional weight of the joists and double flooring, 2x8', 16" on center, the span should be less than or equal 15'-3". This is for barn floors and you said that your span is 15' so it seems that your barn was build to "spec". Slight difference would be with the single floor versus double floor but the weight difference would offset that.

You figure your TS will be 400 lbs and what will the base be, say 2' x 3' so 400 lbs/6 sq ft = 67 lbs/sq ft. So you should up the support by at least 70% (67/40 = 1.675).

If I were you, I would considering doubling up on the 15' joists (sistering) and using joist hangers, put short joists between them every say 16". If you double-up 4 joists, you'll get a 4' working area, 5 joists, you'll get a little over 5' working area (times 15' span). Also I would put another piece of 3/4 plywood under the machinery for extra weight distribution (assuming your not going to move the machinery).

Regards, Joe

[Chris Fite]

Many tables of span for lumber by type and size show that 2x8 span is at a maximum at less than 13 feet. For example:

http://www.cwc.ca/design/tools/calcs/SpanCalc_2002/

[Larry Browning]

Chris,
That's a pretty cool calculator! After looking at that, I am going to check the actual size of the floor joists. I just figured they we 2x8, thinking that was the standard size. They very well could be 2x10. The calculator showed the span to be over 16ft for a 2x10. Even with a 2x10 construction. I think it shows that the jointer would be overweight.
I was thinking that I could get some of those concrete pillers used for decks and set them under the TS and Jointer spaced about 4 ft apart. Then make a sandwich of a piece of 1/2 inch plywood between 2x6's for the beam and place that perpendictular to the joists on top of the pillers. Would that work?

[Chris Fite]

One downside to using the surface concrete supports may be frost heave. I don't know how much of a problem that might be beneath an extant structure or even if the ground freezes where you are. Other than that, your proposal seems to be a good idea.

It seems that it may be a better bet to sister new lumber to the joists and thereby increase the strength of the joists. It makes sense that doubling the thickness of the structure by sistering would double the strength and stiffness, but I don't have any data to support or define this.

[Jeff Sudmeier]

From what I remember two sister joists side by side can carry twice the load. If they are fastened together, they can carry over twice the load, that is the reason that headers are nailed together. If you double up the joists, you an now down to what the floor can support. It will be a mute point if you make sure that the jointer is sitting over the joists, instead of between them. If it was between them, the floor material would have to be strong enough to support the load. If it is on several, the floor is stitting directly on the joists and the jointer is sitting directly above the joist, so all the floor has to do is not compress.

[Larry Browning]

Chris,
Frozen ground is not much of an issue here in Arkansas. Plus, My foundation walls are styrofoam blocks filled with concrete. Also my heating system is radiant heat where the heating tubing is between each floor joist. I just can't imagine it ever getting below 40 under there, let alone cold enough to freeze the ground. The idea of the concrete pillers and support beam would allow me to move the tools to another spot in the future. Just in case I need to make room some new machine that I can't live without. :D
The jointer base is long enought to span at least 2 joists. (I am planning on placing across the joists) and the TS base is almost square, I think it is about 20" square. I can make sure that it catches 2 joists as well.