# joist deflection



## bluebird5 (Dec 13, 2010)

I'm putting in a bid tomorrow on tiling a kitcken and was going to go down in the crawlspace to check th joist size and span. I was getting some numbers ready to ensure they are ok for ceramic tile, but all joists SHOULD be right since 360 is minimum code for floor joists? Anyways john bridge deflectolator and the awc calculators are different by like 1 foot 6 inches. John bridge is more concervative. What calculator or tables you guys use?


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## angus242 (Oct 20, 2007)

bluebird5 said:


> I'm putting in a bid tomorrow on tiling a kitcken and was going to go down in the crawlspace to check th joist size and span. I was getting some numbers ready to ensure they are ok for ceramic tile, but all joists SHOULD be right since 360 is minimum code for floor joists? Anyways john bridge deflectolator and the awc calculators are different by like 1 foot 6 inches. John bridge is more concervative. What calculator or tables you guys use?


Depends on where and when the home was built. Minimum code hasn't always been the same. It's always best to measure. As a rule of thumb, 14' span with 2x10 with 16OC spacing is the absolute minimum for L/360. 

I have my own charts. They aren't electronic and I don't share them. I dish out a lot of info here but some things I do keep to myself. A need some kind of local advantage :laughing:


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## bluebird5 (Dec 13, 2010)

I think you charts might be the deflectolator:laughing: . Thats what they suggested 2x8 11 foot, 2x10 14 foot, 2x12 17 foot. Easy to remember too!


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## TNTRenovate (Aug 19, 2010)

Angus, do you think that 360 is enough? Do you recommend going with 480 if possible?


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## angus242 (Oct 20, 2007)

The stiffer the floor, the better. Ideally, I add an addition layer of 1/2" ply over a 3/4" T&G subfloor that's too close to minimum. I will always use a membrane too. 

However, a membrane is not much more than a bandage to an insufficiently structures subfloor. It is always best practice to structure the floor properly before any other methods are considered.


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