Replies

1. 
   Guest_ | Jan 29, 1999 09:41am | #1

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   To answer your second question first, get the "Well-Connected Structure" catalog from Simpson Strong-Tie. Call 800-999-5099.

   Now, on your first question...

   I dont think you can do anything but re-route. But, if you simply have to find a way, and the building inspector approves, heres my thought...

   Assuming, for purposes of conversation herein, that the mechanical is running through the center of the joist...

   Take your sister piece and lay it under the existing joist, so as to make your marks. Please allow yourself maybe an extra 1/8" , more or less, around things, so fitting will be easier. Then drill your holes, rounding off the edges after your done drilling.

   Once all the holes are drilled, edges of the holes rounded off, cut the joist through the center, lengthwise, so as to cut through the centers of the holes. If the mechanics are off center, find a common-denomiator hole size so your lengthwise cut falls in the center of the mechanics.

   Fit the top. Once sure, re-fit and glue with PL400.

   Then, fit the bottom. Once sure, re-fit and glue with PL400, being sure to glue to lengthwise center cut edges so that the sister joist is glued to its two halves.

   Add joist hangers to both ends, so that the existing joist and sister joist are hanging on the one hanger joist.

   With the glue still wet, drive a wedge from the floor to the bottom of the sister joist, and put pressure at the bottom of the joist so as to press the glue-line at the center of the joist.

   You may want to bolt the joists together, just in center, if the span seems long. But wait until the glue is dry.

   Thats my guess. Please confirm my thoughts before you try.

   Hope this helps.

2. 
   mduval | Feb 01, 1999 09:12am | #2

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   First, why do you need to beef-up your joists? Is it for strength of stiffness reasons? If its to stiffen the floor, a better approach would be to glue and screw 3/8" or 1/2" plywood to the bottoms of the joists (plywood grain parallel with joists). If you still want to get to your utilities between the joists, rip the sheets so that you have 4" on each side of the joists and attach them separately. This will look like a bunch of inverted "T's". the tees are akin to the flanges on structural steel. Flanges resist the bulk of the bending stress anf the web resists the shear. This will stiffen the floor and I believe you will be able to get to your utilities.

3. 
   August_Detbarn | Feb 01, 1999 09:12am | #3

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   Tips on beefing up an existing structure
   first question is how to sister joist with electrical or plumbing lines running through the member