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-   -   22 inch on center joists! please help (http://www.diychatroom.com/f5/22-inch-center-joists-please-help-103517/)

martinzz 05-03-2011 09:10 PM

22 inch on center joists! please help
 
hello all im a newbie to this website. all the help and comments i can get would be highly appreciated. i am installing a 4 1/4 inch wideand 3/4 inch thick t&g red oak hardwood floors. my joists are 2x8, 22 inch on center, for the subfloor it is a 1 x 4 plank runnnig at a 45 degree angle to the joists also it is a semi detached home around a 1000 sguare feet. i was planning on installing a new subloor (3/4 inch t&g plywood 4x8 sheets, glueing and also screwing it down every 8 inches) before i found out my joists are so far apart. any suggestions on what should i do for the subfloor? I want to eliminate any bounce in the floors. Should i just glue and screw the 3/4 plywood over the existing 1x6 planks???

also what size staples and nails are usually used for 3/4 inch hardwood ?

thanks
martin

Daniel Holzman 05-03-2011 10:51 PM

The plywood will not add much stiffness to the floor. In order to compute stiffness of the joists, you need to know the clear span of the joists, the joist spacing (you indicated it was 22 inches OC), the actual depth and width of the joists (an old 2x8 may be full size, modern 2x8 are smaller), and the species and grade of lumber used for the joists. Adding 3/4 inch plywood will stiffen the system a bit, but most of the stiffness comes from the joists.

martinzz 05-04-2011 08:11 AM

Quote:

Originally Posted by Daniel Holzman (Post 641798)
The plywood will not add much stiffness to the floor. In order to compute stiffness of the joists, you need to know the clear span of the joists, the joist spacing (you indicated it was 22 inches OC), the actual depth and width of the joists (an old 2x8 may be full size, modern 2x8 are smaller), and the species and grade of lumber used for the joists. Adding 3/4 inch plywood will stiffen the system a bit, but most of the stiffness comes from the joists.

the clear span of the joists is 20 feet(from side to side of the house) there is only a 20 foot wall supporting it under the living room. Which is the garage wall made out of cement blocks, but the rest of the house has no support for the main floor in the basement. the house is a 45 year old semi detached raised bungalow. the actual size of the joists are 1 3/4 by 3 3/4. There are no visible mark that specify the species and grade of lumber. as for the current 3/4 by 3 3/4 planks that act as the subfloor the only marking on them was a stamp that said standard.

one thing i forgot to mention i do have in my kitchen(11 feet by 11 feet)a 12 by 12 inch ceramic tile sitting on the original subfloor plus a half an inch plywood. there are no cracks anywhere, and its been like tha for atleast 6 years.

should i just go with the extra layer of plywood then? i understand u mentioned that the stiffness of the floor depends on mostly the joists. but could it be that the exisitng subfloor is just old and loose, and thats why it is so noisy, and bouncy in some areas.

thanks

JazMan 05-04-2011 08:43 PM

Hi Martinzz,

In your first post the joists were 2x8, now they're 1 3/4 x 3 3/4" :no: I don't think so. You also say the span of the joists is 20 ft. Again, I don't think so.

Maybe you'll wanna start over? :whistling2:

Jaz


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