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-   -   Floor Joist Advice (http://www.diychatroom.com/f19/floor-joist-advice-135937/)

chrisdjo 03-04-2012 06:16 PM

Floor Joist Advice
 
I'm looking to put in a pool table on the first floor and I'm trying to find out if the floor will support the weight.

4'x8' slate pool table ( 800-1000 lbs )

2x8 floor joists 16" OC
13' span with diagonal blocking mid-span
1/2" sub floor with hardwood on top

The house was built around 1969 and the best I can do to identify the species and grade of the joists is a stamp with (CONST / LP PINE / WWPA Rules)

The existing joists are not notched anywhere.

I anticipate having to sister as many of the joists as I can with 2x8's.

Does this sound reasonable or is this a situation where getting an engineer's inspection is required?

Thanks,
Chris.

sixeightten 03-04-2012 06:25 PM

Your floor appears to be up to code. Putting that weight on the middle of the room will definitely deflect the floor, but not enough to cause failure. Doubling up the joists will definitely help to make the floor more stable and help to keep the table level.

Jackofall1 03-04-2012 06:26 PM

I don't know about a pool table, but I have a baby grand piano on my floor and it hasn't fallen through yet, and I would estimate its weight at, at least 800#, but then again I am not worried about keeping it level as you would with a pool table.

Mark

Yoyizit 03-04-2012 08:53 PM

Measure the floor deflection before and after 1000 lbs worth of your friends stand where the table is going.
If the deflection is 'excessive' experiment with braces.

Daniel Holzman 03-05-2012 08:41 AM

The difference between a pool table and the normal design load for a floor is that a pool table consists of 4 concentrated loads, while the code design for a floor is a distributed load. Common design floor loading is either 30 psf or 40 psf live load, depending on which code you are under, plus about 10 psf dead load. Your floor computes as (barely) adequate for 40 psf distributed live load, which is the maximum I have seen for living room space.

Here is the problem. You are adding approximately 1000 pounds distributed over 4 legs, or about 250 pounds per leg. This is NOT the same as 30 psf distributed live load, it actually has the potential to develop almost twice the maximum moment in the most stressed joist if the table happens to be lined up such that the legs are aligned directly over a joist. The worst case occurs if the two closer legs (I am guessing they are about 3 feet apart) happen to fall directly over a joist, and the center of the pool table is approximately over the mid point of the joist. This is of course likely since you want maximum room around the table for shooting.

You also have to add in the weight of the person who is going to be shooting, since it is pretty common to need to lean on the table to make a shot, which could effectively add 200 pounds or so to the load on one leg.

Conclusion: You have a situation that could easily overstress the floor by up to a factor of 2. I am not saying the floor will break, or even deflect excessively, but it is certainly possible, since your loading is way outside that contemplated by code. I recommend you get the load condition evaluated by the pool table manufacturer BEFORE you install it, else you may have a basement pool table rather than a first floor table.


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