2nd subfloor
I am building a 1,200 sq.ft. one level home with a crawl space in North Central Washington (Zone 6). We have a 3/4″ plywood subfloor and I am currently planning the overall floor level so that the wood stove hearth and heated floor/tile in mudroom and baths are the same level as the rest of the home. I would like to use an LVP or other laminate and will need a second subfloor to bring floor up to the hearth and bath heights. There are so many conflicting recommendations for the second subfloor leading to the following questions. Should the second subfloor be glued to first subfloor? Should the second subfloor be nailed to the joists or just the first subfloor? Should there be padding of some sort between the subfloors?
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Replies
kjenglert,
It would help to know how much height difference you are expecting between the hearth and finished tile floors. LVP and laminate flooring have different transition profiles and thicknesses. There are a wide assortment of tile to flooring edge strips as well. The isolation materials that go under LVP may not be required under a laminate flooring choice that has an integral foam backing.
You may find that the thin underlayment commonly called luan panel is all it takes to make the final stack of materials match up. Be aware that the luan is not always a common fraction of an inch when figuring total stack heights.
Hopefully, the crawlspace will be conditioned to some extent and not be source of moisture drive from below the floor. Again, a few more details will help.
We need more info like onslow stated, but in general, if you need to stack plywood/OSB, you want to lay the second layer perpendicular to the first and for me personally, I wouldn't worry about trying to hit the joists with a 3" screw, I would just use 1 1/2" construction screws and lots of PL Premium glue
Thank you both for helping me figure this out and I apologize for taking so long to get back. The LVP is about 0.2" thick. The hearth with tile, backer board and thinset will be about 3/4". The other tiled areas will be about the same 3/4" height above the subfloor. So, we will likely have about 1/2" difference between tiled areas and the LVP we are considering. Using1/2" ply, 1-1/2" screws, and premium glue seems straightforward.
Depending on the size of the room you can also use self leveler to raise the level slightly. There’s also thicker padded underlayment that can add thickness or some lvp comes thicker. With a transition price, especially a reducer you won’t see or feel the change in heights. As long as you raise the lower floor slightly it won’t take much to notch it all up. I have a few spots that I have 2 different flooring heights and an inexpensive transition price blends it all in just fine.
kjenglert,
It would be best to find dimensioned cross sections of the available edge and transition strips. When I was mating my Pergo to tile floors I found the offered transitions to be quite lumpy under foot. I have the shop capacity to alter the profiles as I wanted and thus lowered the overall profiles. If you do decide to "true up" the levels by adding 1/2" ply or other second subflooring you may find that the frequently flatter transition strips used for pergo to pergo mating more amenable.
Typically, there is no need for padding between the subfloors. The layers should be glued and screwed together directly. Padding is usually used under the final flooring material, such as underlayment for laminate or vinyl plank flooring, to provide cushioning and sound insulation https://www.bestlaminate.com/blog/underlayment-vinyl-plank-flooring/ block blast