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Old 03-20-2012, 02:09 PM   #76
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Securing plank subfloor to joists?


JetSwet - I had thought about replacing the t&g with 3/4" ply, but would like to avoid that if at all possible (we spent a lot of time and maybe 100 bucks putting over 1000 screws trough the planks into the joists).

If I HAVE to do this, I will. I'd just like to avoid it if possible. It may get tricky, as there are a lot of cabinets to work around, but hopefully leaving the t&g under them and putting the ply UP TO the cabinets would suffice (again, if I have no other option)?

So based on ceramic tile's requirement of L/360, am I doing this (see below) right?

Joists are a little over 13' long, with foundation support on one end, I-beam on the other and I-beam in-between. Foundation to I-beam is 6'-3" (to edge, not center of I-beam), I-beam to I-beam is I think 6'-10", or 82". 82"/360 = .2278", or just under a quarter inch (closer to 7/32").

So based off of the longest span (6'-10"), the floor is allowed to sag a maximum of 7/32"? What is a realistic weight to expect this to hold up to? I'd read a good test is to stand on your toes and drop to your heels, but I only weigh about 160 lbs. If I perform this test and the joist sage is <7/32" can I assume it meets the L/360 requirement? What about heavy appliances and moving them across the floor? (I'm sure we'll want to replace our fridge before too long).

Also - could this test be done after the plywood is secure, as this will undoubtedly strengthen the floor and provide for less deflection?

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Old 03-20-2012, 03:20 PM   #77
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Securing plank subfloor to joists?


The deflecto-meter tells you the deflection. Realistic weight is your fatass cousin jumping off a chair after changing a lightbulb.
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Old 03-20-2012, 05:05 PM   #78
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Securing plank subfloor to joists?


So in Other words, if the deflection is <7/32" when I do one thing (for example run across the floor) but >7/32" when I do another (e.g, jump as high as I can and land) the tile will hold up to the first, but not the second activity. It sounds like although there is a standard deflection requirement for tile there is not a standard weight-to-achieve-this-deflection requirement?
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Old 03-20-2012, 06:11 PM   #79
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Securing plank subfloor to joists?


How about going with 3/4" ply instead of 1/2" you will notice a big difference. Will that option end up to high for you?
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Old 03-20-2012, 08:08 PM   #80
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Securing plank subfloor to joists?


Yeah I had wondered if three-quarter would work better. The thing is I already have all the half inch and I've started to attach it (though over a small area). I got the half inch at Home Depot for 12 bucks a sheet. Any idea how much more three-quarter inch would cost?
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Old 03-20-2012, 09:30 PM   #81
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Securing plank subfloor to joists?


Quote:
Originally Posted by duffman56
Yeah I had wondered if three-quarter would work better. The thing is I already have all the half inch and I've started to attach it (though over a small area). I got the half inch at Home Depot for 12 bucks a sheet. Any idea how much more three-quarter inch would cost?
Probably 18 bucks or so, I would go with that.
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Old 03-20-2012, 09:47 PM   #82
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Securing plank subfloor to joists?


Duffman,

Have you confirmed that the movement is because of the joists and not the planks? If the joists are deflecting too much they must be a poor quality in poor condition. 2x6 spanning such a short span should be fine.

Adding the plywood is not gonna improve the joists, just the subfloor. You need to figure out where and how much deflection there is.

When you add the new plywood underlayment make sure you do not buy sheathing. You were just referring to $12 a sheet ply which is the wrong stuff.

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Old 03-20-2012, 10:48 PM   #83
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Securing plank subfloor to joists?


Quote:
Originally Posted by JazMan
Duffman,

Have you confirmed that the movement is because of the joists and not the planks? If the joists are deflecting too much they must be a poor quality in poor condition. 2x6 spanning such a short span should be fine.

Adding the plywood is not gonna improve the joists, just the subfloor. You need to figure out where and how much deflection there is.

When you add the new plywood underlayment make sure you do not buy sheathing. You were just referring to $12 a sheet ply which is the wrong stuff.

Jaz
Jaz, there is nothing wrong with plywood you want to drag it through the mud by naming it sheathing it's meant for what it does and it works.
I always use unsanded cdx and then sanded to tile on
for subflooring. Hasn't failed me yet

He has steal I beam that holds up the joists he's as good as sound, your going to have bounce with 1/2 on old planking.

Raising to 3/4 will tighten up the deflection believe me I have been down this road so many times.
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Old 03-20-2012, 11:58 PM   #84
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Securing plank subfloor to joists?


Had the pro come over tonight. He said we are doing things right and we should be fine. I showed him that the things atop the deep freeze jiggled somewhat when I jumped from a few feet away. He told me this was normal and that every floor will have some give to it. What a relief!

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