floor joists

Hi everyone,

I am remodeling a recently bought home. One of the upstairs rooms is a game room and I plan on putting a pool table (1000 lbs) in it.

The original floor joists were 2x6 16" OC - I glued and nailed another joist on to existing joist - so now it is 4x6 16" OC. If I would add another joist in between, that would make the joist system 2x6 8" OC. The joist span is 13’.

I want to know which one would be better to try.

How can I find out since there are no calculators I can find online that will allow me to get the appropriate spans as a function of sistered 4x6 joists or at a spacing of 8" OC?

The thing is the former owner added a second story, but did not reinforce the 2x6 ceiling (floor for the 2nd floor) joists. He simply laid 2x4’s perpendicular to the “ceiling” joists 16" OC and used a single layer of tounge and grooved 3/4" floor boards. Upon inspection there are many places where the crossing 2x4 do not even tough the underlying joists.

The rest of information: Southern Pine grade #2; dead and live load of 10 and 40, respectively; deflection of L/360.

Maybe you could help me with an exact answer or tell me where should I look to calculate myself.

Thanks in advance!

Since this was originally a single story home, the joists may not be the only thing that was not sized adequately to support a second floor. All elements of the structure, from the foundation up should be evaluated. Since the first floor ceiling has apparently been removed for you to see the joist arrangement, could remodeling of the home include relocation of the game room to the first floor?

Jim King

Go to Western Wood Producers and register, they have two nice calculators which will answer your question.

– bz

As James stated consult a qualified engineer familiar with your type structure and second floor additions to design any alterations to the existing walls/floors.

The monies spent here will save you in the long run.

You can’t rely on just the span tables alone without knowing the design and integrity of the underlaying supporting materials. An engineer can figure this out for you.

Exactly for me to give advice on work I can not see particularly for a none home inspector who I have no idea how much knowledge they have could cause me grief in the future .
I want them to use some one in their area who has the proper qualifications.
… Cookie

A pool table produces, not uniform load, but concentrated load, divided between at least four and possibly as many as eight legs. Much depends on exactly where these concentrated loads will exist. The answer to the question will not be found in any reference source. It should be sought from a qualified design professional who is aware of all conditions which would affect the solution.

The original joists were substandard for the span based on uniform load requirements. The doubled joists may or may not be sufficient for the uniform load required by code, and their ability to carry concentrated loads must be calculated based on absolutely complete information about the existing conditions and the exact location and number of legs of the pool table.

Exactly; and maybe this post http://www.nachi.org/forum/showthread.php?t=22264
Is worth reading again and the title may or could be changed to Where do I put this Pool Table?

Any sub floor framing that will be introduced to a concentrated load should be well analyzed by a structural engineer.

Any span tables will only give you typical distributed load and Code related values and nothing else that could impair the capacities of the system.

Marcel :slight_smile: :slight_smile:

Here is just one example where the structural members below could not support the weight above. Me thinks someone goofed the design or something was not included. This was during the construction process.

Please go ahead and put it on the lowest floor to start with because, if you don’t get the qualified help needed, that is most likely where it will end up anyway.

  1. Slate Pool Table= fun

  2. Slate Pool Table= heavy

  3. Slate Pool Table= basement

  4. Slate Pool Table= on first floor framing/ undesigned, see item #3

Marcel :slight_smile: :wink:

I once remodeled an attic into a 2nd floor living space. The attic had 2x6 floor joists with similar spans. It would have been a big pain in the behind to install deeper joists. The engineer’s solution (suggested by the builder) was to sister a steel c-channel onto the floor joists. He specified a 4" deep c-channel, through bolted with 1/4" bolts, 16" on center. It took the bounce right out of the floor. I even jacked some of the sag out of the floor before installing the steel. Of course we had to verify that the foundation walls and footings, bearing walls, and headers were all capable of handling the additional loads. I only had to add one additional post in the basement to carry the extra weight. The engineering was definitely money well spent on that project!!!

“Click To Enlarge”


Sorry, but the answer to the original question is not found in that or any other joist table. That table does not take into account the concentrated loads that result from something like a pool table, nor does it include doubled joists, and how is one to know which “species group” of lumber one is dealing with? The original question requires specific calculations to answer, and the original questioner would do well to read Mr. Dickerson’s post above for an example of what the proper answer was in his case, not that the same answer will be right in this case.

Anyone who proceeds to modify a structure without consultation from a licensed and insured structural engineer is foolish and will be sorry.

I believe that I can state that no one on this web site (unless an SE shows up) is qualified to comment. If they do, they are opening themselves up to liability.

Hope this helps;

Will, this is an easy one.

The original question at hand does not meet the structural loadings per the IRC structural criteria as framed.

It is inadequate and a pool table that weighs 1000# is completely out of the question until a qualified Structural Engineer assesses the existing conditions as it is.
Pictures would help, but 2 x 6 framing for the span noted in the post is unheard of.

Recommendation for further review by a Structural Engineer is the foremost action needed here.

Marcel :slight_smile: :smiley:

That was my point, Marcel.

It’s all about liability. If a trustural guy makes the call, and is good. No problem.

If he makes the call and is wrong, it’s his liability.

If it even appears that someone on this board made the call (and I didn’t see any posts from “qualified”, meaning willing and able to take the liability, if they are wrong!) then they are left holding the bag when the place collapses. Furthermore, NACHI can also be held liable (stranger legal things have happened, MANY TIMES!).

Recommend evaluation by a licensed and insured structural engineer.

I think Richard is an engineer.

All that is necessary is to adjust the legs on the table to make the surface level in order to allow the balls to travel in a straight line. You guys are way overthinking this crap. If the enginneering is improper or incorrect it only means the legs will require more frequent (daily) adjustment. Eventually, everything will end up being leveled out. Call an engineer.


Richard isn’t an engineer, but he is an architect who is familiar with residential structure. However, as a few have pointed out, answers to questions of this type cannot be given in forums such as this. Why not? Becasue the responder cannot see all the existing conditions which would enter into an evaluation, and cannot be certain that the information provided by the questioner is complete or accurate. To try to respond to a question such as this is dangerous, foolhardy, and, I believe, unethical, in the sense that it is providing, for free, that from which design professionals earn their living, and providing it without full and complete knowledge of the conditions that may affect the answer. All of that does not even begin to involve the difficulties related to assuming liability, which is also a huge concern. I, for one, feel I would be risking my professional license if I tried to answer such questions, and it seems like many here agree with me.

To get an answer to the original question might involve an hour or two of a qualified design professional’s time, if that. I frequently do such things gratis, when I can examine the building first-hand. I would rather people ask me and get an answer free of charge than see them risk doing it themselves, perhaps incorrectly. But only when I can SEE what’s involved.

Worth repeating and well said Richard.

Marcel :slight_smile: :slight_smile: :smiley: