How much of the floor should I pull ?

Scott_K · 08-18-2005, 03:27 PM

Sorry for the delay...reading the above info has confused me some, so I'm still chewing on the info. Thanks.

Ok, so with one of the panels in the basement pulled down, I measured a joist to be 2 1/2" x 8" and they are spaced 16" (measuring from the centers).
The room is 17 x 10 (and change).
Can someone explain L360 ? From what I understand, it is 1" deflection on a 360" span. I'm guessing it's much more complex than that though.

Thanks,
Scott

jproffer · 08-18-2005, 09:39 PM

Go here to figure the deflection:

http://www.johnbridge.com/vbulletin/deflecto.pl

You'll need to know the longest unsupported span, which is, in your case Scott, either 17 feet or 10 feet (unless you have posts or some kind of support in the middle of the room)depending on which way the joists run. The length parallel to the joist is the one we're talking about. If you have 2 1/2 x 8" joists, that's more than a 2 x 8 but to be safe choose the 2 x 8 of unknown wood, that'l be the worst case scenario. Hope this helps. If you have any more questions let me know.

Neil, as I understood your last post, this should answer your question as well, but if not don't hesitate to ask. (sorry it took so long BTW :o , hopefully I'm not too late)

Scott_K · 08-19-2005, 12:03 AM

jproffer, Thanks for the info !

The 10 foot (and change) distance is from the outer wall to a load bearing wall in the middle of the house. I will double check underneath to make sure the length of the joist is held up in the basement. Eyeballing it downstairs, I know there's an I beam running through the house, but I want to make sure it's under the load bearing wall in the middle (I'd assume it would be). There's paneling over it and it's boxed out (probably some pipes there too), so I'm going to have to pull down some more paneling.

Choosing the 2x8,16" on center, unknown and 10 feet, I get L622. At 12 feet it's L396.

A friend of mine told me to jump on the floor. Not very scientific, but he says if you hear it creak or anything, it's not a good sign. Well, jumping around like an idiot, it feels pretty solid.

Thanks Again,
Scott

jproffer · 08-19-2005, 01:05 AM

Yeah, not very scientific, but it works. I've heard of people figuring the allowable flex (based on L360, and yea you were right thats a flex of 1/360th of the length of the floor) so, lets say for simplicity sake, the floor is 360" wide(or long...whatever

), so the allowable flex would be 1", as you stated earlier. I've never seen this, but I've heard about it, and I can't think of one reason it wouldn't work:

Take a step ladder and a can of spray paint. (you see where this is going don't ya?

) Shim it, stack it, and do whatever so the top of the spray can is 1" below a joist. Go upstairs and jump around a while. Come back and check for paint.

I assume this was done in an unfinished basement, but I dunno. If not, I would recommend putting a bag over the spray-paint nozzle and securing it WELL.

DISCLAIMER: This poster, nor this forum shall take any responsibility for husbands performing the spray paint test or the consequences brought about when your wife finds out. No person in any way related to this forum will be held liable for damages, monetary losses (due to alimony), medical bills (due to obvious reasons), or any other loss incurred upon the "spray paint" tester. :D :D

Scott_K · 08-19-2005, 10:36 AM

LOL to the ladder and spray paint....I may have to try that for the humor factor alone. It is a "finished" basement, but I'm planning to re-rock everything, upgrade electric, etc. So right now it's a mess. Any spray paint would probably be an improvement.
Thanks again for your help !

08-18-2005, 03:27 PM	#16
Scott_K Member Join Date: Mar 2005 Location: NY Posts: 73	How much of the floor should I pull ? Sorry for the delay...reading the above info has confused me some, so I'm still chewing on the info. Thanks. Ok, so with one of the panels in the basement pulled down, I measured a joist to be 2 1/2" x 8" and they are spaced 16" (measuring from the centers). The room is 17 x 10 (and change). Can someone explain L360 ? From what I understand, it is 1" deflection on a 360" span. I'm guessing it's much more complex than that though. Thanks, Scott

08-18-2005, 09:39 PM	#17
jproffer Member Join Date: Mar 2005 Location: Chester, IL Posts: 1,141	How much of the floor should I pull ? Go here to figure the deflection: http://www.johnbridge.com/vbulletin/deflecto.pl You'll need to know the longest unsupported span, which is, in your case Scott, either 17 feet or 10 feet (unless you have posts or some kind of support in the middle of the room)depending on which way the joists run. The length parallel to the joist is the one we're talking about. If you have 2 1/2 x 8" joists, that's more than a 2 x 8 but to be safe choose the 2 x 8 of unknown wood, that'l be the worst case scenario. Hope this helps. If you have any more questions let me know. Neil, as I understood your last post, this should answer your question as well, but if not don't hesitate to ask. (sorry it took so long BTW :o , hopefully I'm not too late)

08-19-2005, 12:03 AM	#18
Scott_K Member Join Date: Mar 2005 Location: NY Posts: 73	How much of the floor should I pull ? jproffer, Thanks for the info ! The 10 foot (and change) distance is from the outer wall to a load bearing wall in the middle of the house. I will double check underneath to make sure the length of the joist is held up in the basement. Eyeballing it downstairs, I know there's an I beam running through the house, but I want to make sure it's under the load bearing wall in the middle (I'd assume it would be). There's paneling over it and it's boxed out (probably some pipes there too), so I'm going to have to pull down some more paneling. Choosing the 2x8,16" on center, unknown and 10 feet, I get L622. At 12 feet it's L396. A friend of mine told me to jump on the floor. Not very scientific, but he says if you hear it creak or anything, it's not a good sign. Well, jumping around like an idiot, it feels pretty solid. Thanks Again, Scott

08-19-2005, 01:05 AM	#19
jproffer Member Join Date: Mar 2005 Location: Chester, IL Posts: 1,141	How much of the floor should I pull ? Yeah, not very scientific, but it works. I've heard of people figuring the allowable flex (based on L360, and yea you were right thats a flex of 1/360th of the length of the floor) so, lets say for simplicity sake, the floor is 360" wide(or long...whatever ), so the allowable flex would be 1", as you stated earlier. I've never seen this, but I've heard about it, and I can't think of one reason it wouldn't work: Take a step ladder and a can of spray paint. (you see where this is going don't ya? ) Shim it, stack it, and do whatever so the top of the spray can is 1" below a joist. Go upstairs and jump around a while. Come back and check for paint. I assume this was done in an unfinished basement, but I dunno. If not, I would recommend putting a bag over the spray-paint nozzle and securing it WELL. DISCLAIMER: This poster, nor this forum shall take any responsibility for husbands performing the spray paint test or the consequences brought about when your wife finds out. No person in any way related to this forum will be held liable for damages, monetary losses (due to alimony), medical bills (due to obvious reasons), or any other loss incurred upon the "spray paint" tester. :D :D Last edited by jproffer; 08-19-2005 at 01:07 AM.

08-19-2005, 10:36 AM	#20
Scott_K Member Join Date: Mar 2005 Location: NY Posts: 73	How much of the floor should I pull ? LOL to the ladder and spray paint....I may have to try that for the humor factor alone. It is a "finished" basement, but I'm planning to re-rock everything, upgrade electric, etc. So right now it's a mess. Any spray paint would probably be an improvement. Thanks again for your help !

How much of the floor should I pull ?