Should I raise my subfloor when moving from 3/4" hardwood to thinner laminate?
Do what you can live with. If it means laying down 1/4&quot; underlayment everywhere, do it. Especially if the floor has issues, whether minor or major, that an additional layer of underlayment will assist in correcting. Do straight edge the floor beforehand to make sure it is within the install guidelines for flatness.
When I changed the flooring in the house we have now, there were 4 different types of flooring on a slab on grade. Glued down 3/4 X 2 1/4&quot; maple, 3/4&quot; x 3 1/4&quot; &quot;floating&quot; T&amp;G maple, not glued or anything like that, carpet and click lock laminate. I installed vinyl click lock that was only 3/16&quot; thick in its place. Gaps at the trim where the flooring was pulled up, to look at the gaps left over was more than I chose to live with. I used a gauge block and oscillating saw to cut all the trim bottoms the same, and set small pieces (about 7/8&quot;) of matching trim carefully in place with wood glue buttered on both cut faces to hold it there. There was only one door jamb that was an atrocity, and from another door jamb that was demoed, I cut a portion to fit under the recut jamb to fill it in. It all blended in rather nicely. Much better than the gaps. More economical too.