vinyl plank flooring is separating

[Sol Bergren]

I've installed vinyl plank flooring in a rental, I really like it but it keeps separating (I helped install this with someone who has installed alot of flooring previously but never the vinyl plank type, so maybe we did something incorrectly).  

Has anyone else had this problem, I've removed the baseboards and tapped it back together once already but it continues to separate, not really sure what to do, it looks great and holds up super well, except for the gaps!  Anyone have suggestions or encountered this problem??

[Bob H.]

Based on my experience with engineered hardwood, I doubt that you need to remove baseboards. After seeing a video somewhere, I made the tool in the photos, using wood, some screws and stick-on rubber safety tread from Harbor Freight: https://www.harborfreight.com/self-adhesive-rubber-safety-step-tread-98856.html. Just put the tool on one of the boards that has a gap and hit the slanted end with a rubber mallet. It took about five minutes to close the gaps in my floor. A few of them opened up again, so a few months later I repeated the process but put a little wood glue in the cracks first. Not enough time has elapsed to tell if the glue will be a permanent fix. 

I don't know the cause of this problem, but in other areas of this floor you can feel low spots where the concrete slab was not completely level before the flooring was laid.