I am planning to sister each 2X joist on a kitchen floor with a LVL joist of the same height and length. Simpson Strong-Tie makes great structural screws – the SDW series – for sistering and multi-ply beam applications. I want to use construction adhesive such as Loctite PL Premium between the dimensional lumber and LVL in addition to securing with structural screws.
Most LVL manufacturers add a water resistant coating at the factory to provide protection from the elements during the building process. Would PL Premium adhere adequately to this water resistant coating or should I sand off the coating on the mating surface before applying the adhesive?
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Years ago, on a commercial job, we had to remove that coating so the construction adhesive would grab. We rented a floor sander, and sanded the beams.
This was required by the architect/engineer.
Thanks, Shep. Looks like the architect on your old commercial job agrees with my intuition. Using a floor sander is an excellent idea. It will really speed up the job. Thank you.
On a related note, here are some excellent resources on using structural screws for multi-ply beams made with multiple 2X lumber or LVLs (the first article addresses LVLs only).
• http://internationalbeams.com/wp-content/uploads/2012/12/TB-LVL-2.pdf
• https://p.widencdn.net/ytyjnh/C-F-2019TECHSUP-p90-97.pdf
Sistering essentially creates a multi-ply beam except you often reinforce dimensional lumber with LVL. Simpson Strong-Tie engineering team tells me that you can use their SDW22300 screw and drive from the dimensional lumber side into the LVL. This way, the entire threaded part of the screw will be embedded in the LVL. You want the entire threaded region to be in the last member in the multi-ply beam to get the best clamping effect.
On my project, for sistering existing 2x10 joists (they are more like 9-1/8" wide after 50+ years in the floor), I plan to use 1.75" x 9.5" LVL of the same length as the dimensional lumber, ripped to match the 9-1/8” width of the 2X joists, and use two rows of the SDW22300 screws. The screws by themselves should provide enough reinforcement. However, I plan to also use PL Premium between the 2X lumber and sanded LVLs. The Simpson Strong-Tie team has not done any testing with the use of adhesives in multi-ply beams. But they agree it could only make the beam stronger and couldn’t hurt.