Replies

1. 
   jonblakemore | Feb 21, 2003 09:27pm | #1

   More information please:

   Why are you doing this?

   What is the size of the existing floor joists?

   What is the span?

   Any unusual loads above that will bear on the joists?

   Jon Blakemore
1. 
   EdJW | Feb 24, 2003 07:17pm | #9

   Jon, I have 3x12 floor joists that span 22 feet.  There is about and inch and a half sag in the middle.  I also need to raise the floor an additional inch to meet up with a concrete slab that we are expanding the kitchen into.  Rather than ripping long shims/sleepers I thought that I could accomplish raising and strengthening the floor by sistering LVL's.  The LVL's would be supported on both ends just as the existing floor joists.  There is one bearing wall that carries the ceiling joists only (ranch).  Looking at the other posts, the screws seem like the way to go.  I see that McFeely's has similar screws to the Simpson's as mentioned in a later post.  -Ed

1. 
   BossHog | Feb 24, 2003 10:03pm | #10

   With joists 22' long and about 12" deep, nothing you add to the side of the joists is likely to help much. The length/depth ratio is just too bad.

   You'd probably gain a lot more stiffness by adding a center beam. Or at least don't buy too many of the LVLs right off, and see how much difference it makes before you drop a bunch of money on it.How can "quite a lot" and "quite a few" mean the same thing?

2. 
   Ward | Feb 22, 2003 11:22pm | #2

   A posting last on a the same subject noted that the manufactures specifically siad not to glue the faces.  I would speculate this could cause delamination of the glue layer.

   I would lean towards screwing the LVL's to the joist.  That keeps the layers tighter than nailing over a long period of loading.  i/e of you are planning on trying to straighten the old joist and then put the LVL's on.  If the layers are allowed to seperate (nails working loose) you won't have the support you wanted and squeeks or humps may apear.

   The other important area is where the joists are seated.  If the LVL's don't have a good bearing on the sill, plate etc, than you aren't helping the structural integrety of the building, you are mearly flattening the floor.

   Good luck

3. 
   Timuhler | Feb 23, 2003 02:41am | #3

   Check out the manufacturer's guide.  The LP guide I have shows the schedule for nails and lag screws.  Another guide I have (cascade capitol) shows the schedule for those new Simpson SDS screws that don't require predrilling.  I think the box I bought was 10$ for about 50.  I'm not sure though on the price.  I recommend that as the way to go, but check with the manufacturer.

4. 
   archyII | Feb 23, 2003 02:48am | #4

   I would use thru bolts.  If your going to drill for lags why not use bolts.  As the other posters stated check with the manufacturer (they all have different rules).

1. 
   Bruce | Feb 23, 2003 09:59am | #6

   Do bear in mind that drilling for thru bolts means a hole tight enough that the bolts must be driven in, or the LVL sister is totally wasted.

1. 
   UncleDunc | Feb 23, 2003 10:43am | #7

   That doesn't seem right. If shear strength is all the bolt contributes, why do we even bother bolting them together. We could just drill the hole, drive a pin in and be done with it.

   Surely the high friction between the two pieces, caused by the pressure of the bolts holding them together, plays some part in resisting shear stresses.

1. 
   Bruce | Feb 23, 2003 06:46pm | #8

   You're absolutely right that the friction plays an important part in transferring the load from the joist to the LVL.  But do you want to totally depend on the compression of the bolt to maintain that friction over time?  It isn't that the bolt is contributing shear strength, but rather that it's preventing the two members from creeping against each other if the frictional force isn't doing the job.  If the holes are tight, you can depend on the surface area of the bolt to transfer the load from one member to the other.

   Edited 2/23/2003 10:55:30 AM ET by BEMW

5. 
   stossel1 | Feb 23, 2003 04:30am | #5

   My current job has several load bearing LVL's and all i do is nail them together.  Four  12d's on 16" centers.