Replies

1. 
   BossHog | Mar 07, 2003 05:26pm | #1

   How much money ya got?

   Might help if you'd tell us what you're trying to do.

   Let him who is without aim cast the first stone.

1. 
   Kneeofyte | Mar 07, 2003 05:43pm | #2

   Hah! I want to reinforce the floor joists under my family room. The house is about 40 years old so the existing supports are wood and nailed into the joists. Many of them have fallen out over the years. I want to replace them with metal supports.

1. 
   BossHog | Mar 07, 2003 06:40pm | #4

   The title of your post: "Floor Joists: Bridge Supports" led me to believe you were asking about joist spacing to use in building a bridge.

   Bridging/cross bracing between joists is the subject of much controversy. (They AREN'T suports, by the way) Some say they help, others say they cause problems and don't help. Take your pick.

   Why do you feel you need them? Is your floor springy? If not, you could just take the old wood ones out and see how much difference it makes.It may be a small world, but I'd sure hate to paint it.

1. 
   Kneeofyte | Mar 07, 2003 07:36pm | #6

   Yes, I'm referring to bridging/cross bracing between joists. There are two reasons why I asked the question. The existing wood cross braces are old and falling off. And when people walk across the family room floor, I hear wood crack. It's not loud cracking, but the noise concerns me. Underneath there is no evidence of cracked floor joists - everything looks to be in good structural condition.

1. 
   BossHog | Mar 07, 2003 08:44pm | #9

   It could be that the bridging itself is what's causing the noise. Taking it off is the only thing that's going to tell you that.

   I doubt adding any sort of bridging/bracing back in will help with floor noises.Sometimes you're the bug and sometimes you're the windshield.

2. 
   Kneeofyte | Mar 07, 2003 08:50pm | #11

   Yes. It's not the noise that bothers me but the nagging suspicion that something could be wrong - an underlying problem (no pun intended). As i said, the joists appear solid and are sitting on the house sill on both ends.

3. 
   MikeSmith | Mar 07, 2003 09:44pm | #12

   take the bridging out and furr your ceiling... if there are any split joists , sister a repair alongside before you furr it... or firr it..or however it's spelledMike Smith Rhode Island : Design / Build / Repair / Restore

2. 
   Qtrmeg | Mar 07, 2003 06:38pm | #3

   I don't know, Boss, maybe he is talking about bridging?

2. 
   rez | Mar 07, 2003 07:07pm | #5

   Hiya Knee- Your profile tells us that you're 80 years old. Is that right?

    

    

1. 
   Kneeofyte | Mar 07, 2003 07:37pm | #7

   Yep, and I have a bad hernia and take Metamucil every day : )

1. 
   rez | Mar 07, 2003 07:43pm | #8

   Ha!  What size floor joists do you have there and how long is the span?

   Paradise? Is that in New England or Arizona?

    

    

   Edited 3/7/2003 11:44:44 AM ET by rez

1. 
   Kneeofyte | Mar 07, 2003 08:46pm | #10

   The family room floor is tile. The joists span 15 ft. and measure 2"x10".

   I'm here in New England so I suppose one could say that paradise is almost here...in a month (fingers crossed).

1. 
   Piffin | Mar 08, 2003 12:17am | #18

   Getting advice from us sometimes is like getting a firm answer aout of a politician isn't it?

   Let me answer this way - if I were buiilding new, and didn't need to furr down the basement ceiling for finishing, I would put the bridging in halfway along the 15' span at aboput 7.5'

   If I were a bridging kind of guy, that is. I generally prefer solid blocking between at same interval or furring under.

   BTW, that 15' span is quite a challenge for 2x10@16"oc. That is probably why the cracking sounds but it could be half a dozen other things going on too. Any possibility of setting a beam and posts under there?.

   Excellence is its own reward!

2. 
   Qtrmeg | Mar 08, 2003 12:42am | #19

   Ya, I suppose we always have the option to answer properly. ;-)

   I agree the 15ft span is about the max, especially for a tile floor, so keep the dancing to a minimum. I would guess the cracking is mostly from the remaining solid blocking, (has it been determined that that is what is there?), seeing as some is falling out. So what to do?

   Secure the remaining blocking, if possible, and replace what is missing? You are likely to split more than you save, so pre-drill for toenails? Still won't prevent all the noise, so maybe run a bead of construction adhesive along the sides? Sounds like a science project.

   Remove the blocking and strap? Sounds like the best plan, right next to doing nothing.

   A beam would be nice.

   Want to know what I would never do? Install metal bridging.

3. 
   MikeSmith | Mar 08, 2003 01:32am | #20

   i actually did install metal bridging once.. but i was young and foolish then.. now i'm just foolish..Mike Smith Rhode Island : Design / Build / Repair / Restore

4. 
   Piffin | Mar 08, 2003 02:49am | #21

   Last metal bridging I nailed up was in 1972 - and I'll bet even odds that those places are torn down by now.

   Excellence is its own reward!

5. 
   stefs3 | Mar 08, 2003 02:52am | #22

   Why not metal bridging?

   Stef

6. 
   Piffin | Mar 08, 2003 04:10am | #23

   It is made to be jammed in after the fact instead of installed in process. There are no nails at the top joint, only the little metal spur tabs to jam into the wood. That works in constant tension which is fine if you assume such.

   They also are extremely easy to bend or knock out.

   You also want to be sure to wear aya protection because you would be installing up overhead and the flecks of galvanized metal being knocked off by your hammer will mnake a bee-line for you eye sockets and scratch your corneal lenses - a painfull experience.

   solid wood blocking or furring is far the better and stronger job. Perhaps your s were not well nailed in the first place. it is often a job assigned to the new guy on the job..

   Excellence is its own reward!

7. 
   Kneeofyte | Mar 08, 2003 04:54pm | #24

   The existing diagonal bridges are puny so it sounds like solid bridging between the joists should help. What size blocking should I use and what is the correct way to nail it into the joist?

   You mention that the 2x10 is carrying a heavy load given the tiles above. What size joist would you have used? Would it make sense to add sister joists with lag bolts?

   Actually, I can't use beam and posts. The basement floor under these joists was a dirt (why the heck do builders do this?), so about two years ago I paid a company to pour a lightweight concrete product which sealed it pretty well. The floor could not support the weight.

   BTW, if I'm using any incorrect construction terms please correct me. All of this is new to me.

   Thank you.

   Kneeofyte

   P.S. And thanks to everyone else for their advice. All of the points raised have been on my mind including the dubious installation instructions for metal cross bridging suggested by the manufacturer.

8. 
   Piffin | Mar 08, 2003 05:26pm | #26

   Technigcally, you have approximately enough for the span, but it is at about maximum. Building new, I would use 2x12's though.

   You are probably not suffering failure but having more of a problem with bounce/vibration. so the beam in the cellar would still work if this is an open span above because it would only be supporting the flor to keep it from bouncing. Just use a steel plate to spread the load at bottom of the jack post.

   Even if you did want it to be more structural beam, it wouldn't take much to cut through that lightweight and dig down to pour a pad about 12"x12" or up to 18"x18" and six or eight inches deep. Or you could buy a precast concrete cookie to just place there on top of the mudslab.

   anything like this would be easier than all that sistering, unless you plan on finishing off the basement someday.

   terms - I originally thought you had blocking and that was what was falling out. It sounds like you have wood bridging now - wood nailed diagonaly crossbucked between the joists.

   Solid blocking is same size as joists - 2 x 10 for you, cut to the length to fit snug between joists which is 14.5" each IF they were all perfect.

   Seat then in bu toenailing or by through nailing from opposite side of joist. You can offset them from each other 1-1/2" to do this.

   Furring method is this - you get furring strips also called strapping - 1x3's and do a layout on the bottom of the joists every 16" perpendiculat to the joistset. Nail the strapping straight up into the joists. That creates a sort of snadwhich effect to reduce bounce..

   Excellence is its own reward!

9. 
   rez | Mar 09, 2003 05:18am | #27

   Knee-  So you're spanning 15 foot with 2x10s, a grouted ceramic tile floor is upstairs and you can hear light wood cracking sounds when some one is walking on the floor. 

   Hopefully the cracking noises are the remaining cross bridging. I would think a beam midspan would be best. However, if you decide not to go that route and decide to use the solid wood bridging in place of the diagonal cross supports you have in there now, maybe strapping in addition to the bridging would give you better assurance that you have tackled the problem successfully.

   What I like to do with the solid bridging is after a straight chalk line is made across all the joists from wall to wall, first nail the 2x10 bridging pieces tightly between every other joist following the chalk line. Make these tight where they have to be tapped in with a hammer with no gaps showing between the edges of the bridging and the joists. This can be time consuming if the joists are tweaked to any degree since a perfect 90degree cut on each end will leave a gap but a 40 year old house shouldn't have that problem. It's best to measure and cut each piece to assure a tight fit thru any variables that might occur in the joist spacing.

   Then go back and fill in the empty joist spaces you just left, with bridging pieces you measure and cut individually to fill that void. At this time the trick is to slightly cut the bridging piece longer by a 1/16" or 1/8", something like that but you won't know until you hammer them in to those spaces.

    The idea is to give an overly tight fit here that must be forcefully hammered into place, the edge of the bridging piece possibly digging slightly into the joist in the process.

    This is to assure a tight fit all along the bridging run from wall to wall, keeping the joists in a desired tension to lessen or prevent any movement. Any looseness in the bridging could dramatically lessen the impact on the floor.

   With this tight of a fit all the bridging pieces can be in a continuous line and that second bridging run that filled the voids can just be toenailed into the joists with one nail in each bottom corner.

   That and the furring should be about the best you can do short of sistering in more joists.

   Of couse that is just my humble opinion.

    

    

   Edited 3/8/2003 9:24:31 PM ET by rez

10. 
    Piffin | Mar 09, 2003 06:50am | #28

    I'm sitting here thinking about all this pounding and thumping and hambering to send strong shudders through the floor membrane where the adhesion of the floor tiles may already be challenged and winder if they will survive.

    What you said about tight fits is great for new work but just snug is good for remodel and repair. Also, A lot of times i use structural screws in marginal areas like this so the vibrations don't damage whatever is oin the other side.

    Not to be critical - just a word of caution....

    Excellence is its own reward!

11. 
    rez | Mar 09, 2003 07:54am | #29

    Ya, good point, especially if that ceramic tile floor is original with the house.

     

     

12. 
    Kneeofyte | Mar 08, 2003 05:01pm | #25

    Regarding your comment, "getting advice from us sometimes is like getting a firm answer out of a politician isn't it?". As we all know, that's the power of this forum: different opinions based on various experiences. It's the socratic method more or less. Er, Carpe Diem.

13. 
    JohnSprung | Mar 11, 2003 03:19am | #30

    Actually he didn't say what the center distance was.  16" OC would be NSG, but if it's 12" that could be OK.

    Mid-span blocking acts to resist the tendency of the bottom edge of the joists to deflect in a direction perpendicular to the joist.  When that happens, the floor gets real bouncy.  Blocking will help or not depending on whether that's the problem or not.

    -- J.S.

3. 
   NickNukeEm | Mar 07, 2003 10:39pm | #13

   Love the name.  Neophyte, meaning new, for an 80 year-old guy.  Nice play.

1. 
   Kneeofyte | Mar 07, 2003 11:13pm | #14

   Oh, thank you. Come to think of it, my knees aren't quite like they used to be either. Always fighting to put them back into joint : )

1. 
   FrankB89 | Mar 07, 2003 11:24pm | #15

   If you're 80 years old, it's very possible it's your joints that are making the noise.  Might want to get an appointment with an Orthopedic surgeon, or do a search for a recent discussion about curing body-ills with magnets.

   :-)  Good luck! 

1. 
   Qtrmeg | Mar 07, 2003 11:25pm | #16

   Ya, but there's nothing wrong with his hearing. ;-)

1. 
   Kneeofyte | Mar 07, 2003 11:33pm | #17

   Huh? Did that "Tiny Yapper" say something about an ortho. surgeon?

   http://www.winternet.com/~mikelr/flame7.html

   I couldn't resist. It's good clean fun - Peace