Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > Building & Construction

CLICK HERE AND JOIN OUR COMMUNITY TODAY...IT'S FREE!

Reply
 
Thread Tools Search this Thread Display Modes
Old 02-04-2010, 06:45 PM   #1
Member
 
Join Date: Nov 2007
Location: Appleton, Wisconsin
Posts: 935
Rewards Points: 500
Default

what size beam for jacking up floor joists


I posted my sagging floor joist issue a couple weeks ago and have decided on jacking up the existing floor joists using a temp beam supported by 4 columns at the middle of the floor joists. Then when all is level I will sister 2x10s to the existing 2x8s. My question is what size beam should I use for the temp beam? The beam will be 23 feet long and I'm thinking 4 support columns, one at each end and 2 in the middle so it would be right around 7 ft in between each column. This temp beam only needs to support the middle of the floor joist and what's on them. There is no supporting walls on top of it so it doesn't need to hold the whole house up. I'm thinking that double 2x6 or 2x8 should do for this? Here is a drawing that helps to explain the situation.

what size beam for jacking up floor joists-basement-support.jpg

ponch37300 is offline   Reply With Quote
Old 02-04-2010, 07:00 PM   #2
Member
 
Join Date: Nov 2009
Location: central virginia mountains
Posts: 1,857
Rewards Points: 1,000
Default

what size beam for jacking up floor joists


how you getting the 2x10 over the beam

__________________
The older I get the better I was
tpolk is offline   Reply With Quote
Old 02-04-2010, 07:18 PM   #3
Member
 
Join Date: Jul 2007
Location: Jacksonville, FL
Posts: 886
Rewards Points: 500
Default

what size beam for jacking up floor joists


Can you post a link to your previous postings on your floor joist issues?

It might help us or at least me understand why you are taking this approach. Is the sag uniform at the middle for 23 ft? What does the string tell you?

what is your plan for sistering the 2x10 to the 2x8 at the temp beam area. notch your temp beam or block up directly under the 2x8 from the temp beam. OR Notch the 2x10 around your temp beam?

Think about renting some post shores (screw jacks).

Let us know.
Big Bob is offline   Reply With Quote
Old 02-04-2010, 08:29 PM   #4
Member
 
Join Date: Nov 2007
Location: Appleton, Wisconsin
Posts: 935
Rewards Points: 500
Default

what size beam for jacking up floor joists


Here is the link to my other thread Need to add floor support. The floor is sagging becuase it has 2x8s spaced at 16" that span about 15'.

I bought 4 "screw" jacks since I'm not sure how long this project is going to take so renting might get a little expensive.

I plan on using a spacer in between the beam and existing 2x8s so I can slid the 2x10s in. I'll have to do a test to see if I can slide them in with the temp beam in place.
ponch37300 is offline   Reply With Quote
Old 02-04-2010, 08:36 PM   #5
Member
 
jlhaslip's Avatar
 
Join Date: Dec 2009
Location: Canadian Rockies
Posts: 1,280
Rewards Points: 500
Default

what size beam for jacking up floor joists


Don't forget that you need to be careful with the bottom of the jacking system.
It will be placing a whole bunch of weight onto the floor system it is raised on.
Check to see if you need to support the floor underneath with other jacks/posts before they get loaded up.

Best to carry the temporary loads all the way to the basement/ground.
__________________
Quote:
Originally Posted by Bud Cline View Post
Go ahead and apply for a variance, those guys at City Hall can use a good laugh.
jlhaslip is offline   Reply With Quote
Old 02-04-2010, 09:59 PM   #6
Member
 
Join Date: Nov 2007
Location: Appleton, Wisconsin
Posts: 935
Rewards Points: 500
Default

what size beam for jacking up floor joists


Quote:
Originally Posted by jlhaslip View Post
Don't forget that you need to be careful with the bottom of the jacking system.
It will be placing a whole bunch of weight onto the floor system it is raised on.
Check to see if you need to support the floor underneath with other jacks/posts before they get loaded up.

Best to carry the temporary loads all the way to the basement/ground.

This will be in the basement to jack up the first floor so as long as the cement which is in pretty good shape can hold the weight I'll be alright.
ponch37300 is offline   Reply With Quote
Old 02-04-2010, 10:09 PM   #7
Member
 
jlhaslip's Avatar
 
Join Date: Dec 2009
Location: Canadian Rockies
Posts: 1,280
Rewards Points: 500
Default

what size beam for jacking up floor joists


Quote:
Originally Posted by ponch37300 View Post
This will be in the basement to jack up the first floor so as long as the cement which is in pretty good shape can hold the weight I'll be alright.
I would still place some 2 by's and plywood under the system to spread the weight around.
Do you know how thick the concrete is or are there footings near there? Better to jack at the footings.
__________________
Quote:
Originally Posted by Bud Cline View Post
Go ahead and apply for a variance, those guys at City Hall can use a good laugh.
jlhaslip is offline   Reply With Quote
Old 02-04-2010, 10:21 PM   #8
Member
 
Join Date: Nov 2007
Location: Appleton, Wisconsin
Posts: 935
Rewards Points: 500
Default

what size beam for jacking up floor joists


I was thinking about laying a 2x12 about 2 feet long down flat to help spread the weight a little. I doubt there is any footers in the middle of the slab. The post on each end of the beam should be close to footers since they will be by the foundation wall, but the two posts in the middle probably will just be on the slab.

Thanks
ponch37300 is offline   Reply With Quote
Old 02-05-2010, 10:07 AM   #9
Newbie
 
Join Date: May 2009
Location: Chicago suburbs, Illinois
Posts: 23
Rewards Points: 10
Default

what size beam for jacking up floor joists


I have a brick fireplace being held up from the basement that is on 2x8 joists with screw jacks. I still see concrete cracks even though the previous owner used 1 2x8 wood under the jacks.
scott j is offline   Reply With Quote
Old 02-05-2010, 10:14 AM   #10
Member
 
Join Date: Nov 2007
Location: Appleton, Wisconsin
Posts: 935
Rewards Points: 500
Default

what size beam for jacking up floor joists


I think I'm going to cut 2 foot long peices of 2x12s and a peice of 3/4 plywood 23"x24" and make a pad that will have 2 2x12s under a peice of 3/4" ply and hope for no cracks. This should spread the weight out over a 2x2' area. This is just going to be a temp beam and posts, just using it to raise the joists and level things out before I add the sister joist.
ponch37300 is offline   Reply With Quote
Old 02-05-2010, 03:05 PM   #11
Member
 
Join Date: Jul 2007
Location: Jacksonville, FL
Posts: 886
Rewards Points: 500
Default

what size beam for jacking up floor joists


tpolk and I cross posts... but I think the same thing has got us scratching our heads.

your in a basement.. assume these are solid walls and you don't have a row of window to stick the boards out...

I don't think you will have enough angel to get the full length sister board in place once the beam is in place. Maybe with a good fire cut end...?

1. I guess you could tack the sisters in place then set your temp beam.

2. If it were my project I would forget the temp beam... run a lot of string and line levels... keep them tight... once every hour... and work the sisters in one at a time. I think that beam is going to be in your way alot.

You might want to try a dry run and see how your plan is going to work.
Big Bob is offline   Reply With Quote
Old 02-05-2010, 03:25 PM   #12
Civil Engineer
 
Join Date: Mar 2009
Location: Boston
Posts: 4,250
Rewards Points: 2,078
Default

what size beam for jacking up floor joists


I'm with Bob, I cannot visualize the advantage of your approach versus jacking up each joist individually, of course very slowly, until it is level, then sistering the new joist to it. One jack, one pad, no interference. The only advantage I see about the beam is you get to jack all the joists simultaneously, but I don't see how this will save you any time, considering the difficulty of setting up the beam and jacks, advancing each jack individually, checking each joist for level, etc.

By the way, the joists you jack up to level are going to be under considerable stress because you are changing their shape. You are going to need a lot of nails or structural screws to adequately connect the new joist to the old joist. Also, after you release the jack, the paired joist is going to move downward due to the release of energy in the old joist, so if you are looking for a level floor, you are going to need to overcompensate during the initial jacking. Exactly how much will depend on the species of wood, dimensions, amount of deformation of the joist, and the location of loads above the joist.
Daniel Holzman is online now   Reply With Quote
Old 02-05-2010, 05:44 PM   #13
Member
 
Join Date: Nov 2007
Location: Appleton, Wisconsin
Posts: 935
Rewards Points: 500
Default

what size beam for jacking up floor joists


I was thinking that putting a temp beam in would allow me to raise the whole floor at once, avoiding raising one joist and not the one next to it. Just thought that it would be a lot of stress on the sub floor if I raised one joist and not the one next to it. I was planning on giving this a test run to see if I can slide the new joists in over the beam. It would probably be faster to do it without a beam but I was worried about the stress on the other joists.

I'm not necessarily trying to get a perfectly level floor, more trying to stiffen up the floor because it has a "bounce" to it.

Thanks again for all the advice and ideas!

Last edited by ponch37300; 02-05-2010 at 06:01 PM.
ponch37300 is offline   Reply With Quote
Old 02-05-2010, 11:58 PM   #14
Member
 
Join Date: Jan 2008
Location: Alabama
Posts: 608
Rewards Points: 500
Default

what size beam for jacking up floor joists


My thoughts are along the same lines as Bob.

You could jack the floor up on joist at a time if you first block all the joists together. That way as you jack one joist up, the blocking will pull the neigboring joists up with it. Presumably it won't put much strain on the sub-flooor. Conceptually as you jack one joist up 1", the next joist will raise 3/4", the next on 1/2", etc. You could even use a short beam to jack the neiboring joists up in this type of pattern. At one end of the beam, jack it up to level the floor. The other end just barely jack the joist up. As you get one joist sistered, move the system down to the next joist. To avoid raising and lowering the floor, use two beams. Rather than take down the 1st beam, use the 2nd beam to jack the next set of joists up.
HooKooDooKu is offline   Reply With Quote
Old 02-06-2010, 08:14 AM   #15
Member
 
Join Date: Nov 2007
Location: Appleton, Wisconsin
Posts: 935
Rewards Points: 500
Default

what size beam for jacking up floor joists


Quote:
Originally Posted by HooKooDooKu View Post
My thoughts are along the same lines as Bob.

You could jack the floor up on joist at a time if you first block all the joists together. That way as you jack one joist up, the blocking will pull the neigboring joists up with it. Presumably it won't put much strain on the sub-flooor. Conceptually as you jack one joist up 1", the next joist will raise 3/4", the next on 1/2", etc. You could even use a short beam to jack the neiboring joists up in this type of pattern. At one end of the beam, jack it up to level the floor. The other end just barely jack the joist up. As you get one joist sistered, move the system down to the next joist. To avoid raising and lowering the floor, use two beams. Rather than take down the 1st beam, use the 2nd beam to jack the next set of joists up.
This sounds like a good method. I have 4 jack posts right now so I can get one more and then will have enough to jack one truss up and also have 2 beams so I can just keep going. This idea eases my questions about raising one beam at a time. Thank you all for your suggestions.

ponch37300 is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
What size beam to support loft with 16' between supports paperman Building & Construction 3 10-06-2009 05:40 PM
Correct Beam Size ericw1 Building & Construction 1 07-29-2009 11:46 AM
Crawl Space Beam and Joist Support Questions Fire4Effect Building & Construction 5 06-28-2009 01:07 PM
Beam Size Wildie Building & Construction 22 09-18-2008 08:35 PM
Beam Size sevver Carpentry 15 04-30-2008 12:51 PM




Top of Page | View New Posts

Copyright © 2003-2014 Escalate Media. All Rights Reserved.