Laminate flooring today is usually sold as glueless, "floating'' floor systems, which means the boards snap together like puzzle pieces and sit unattached to the house. The floor trim around the edges holds it all down. Floating floors can be installed over any existing hard floor surface, but should have an underlayment between the laminate flooring and the subfloor. You can buy laminate underlayment, but if you have a bunch of old roofing felt, it works just as well.
Remove the floor trim, using a hammer and pry bar. Don't damage the trim as you remove it. Set it aside.
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Sweep and mop the floor. Let it dry completely.
Roll out a course of roofing felt on the floor alongside the wall where you want the flooring courses to start. Cut the felt at the end, against the perpendicular wall, by laying a level across the width of it and running a utility knife along the level. Flip the piece of felt over, so it's not curling up at the ends.
Roll out the next course of felt in the same manner, cutting it and flipping it over. Lay it so the long edge of the new course is butting up against the long edge of the previous course, but not overlapping.
Press a long strip of duct tape over the whole seam between the two courses of felt paper, attaching them to one another. Don't tape them to the floor.
Lay additional courses of felt paper in the same manner, until the whole floor is covered. Cut the last course length-wise as needed to make it fit.
Lay your floating floor directly over the felt paper, starting at the same wall and fitting the floor planks together end to end and alongside one another. Leave 3/8 inch of space between the edges of the floor and the wall on all sides. Cut the end boards as needed on a miter saw. Length-cut the final course of flooring on a table saw to fit, if necessary.
Re-install your floor trim using a trim nailer to cover up the gaps around the edges of the floor.