# Subfloor for laminate installation



## soandso

So I have a 100 year old house that I want to install laminate flooring in.

There was carpeting which I removed, and pulled out the baseboards (they  had carpeted the baseboards!) so what's left is the original planks on top of the joists.

The original flooring I'm guessing is quarter sawn pine/fir. A lot of the boards are pretty mangled from electrical work, some are splintered like they literally ripped them up. There are also a lot of screw holes, cross-cuts, and the cracks are pretty drafty over the front porch, so I've kind of already decided not to refinish them.

So my question is, should I put a layer of plywood down to even out the floor first, or can I get away with just an underlayment?

Another consideration is I'm trying to keep the total thickness to 1" to meet the height of the beveled marble threshold to the bathroom. 

Would 3/8"  plywood be enough? Would I screw through to the joists, nail to the boards, or float the ply?






















Thanks!


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## johnjh2o

If you raise the height of the flooring you better plain on raising the baseboard heating. Baseboard heat depends on convection as well as radiation to prudence heat. With the space below the baseboard closed off you will lose the convection thus reducing the heat output.


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## soandso

Yes I've thought of that. I have a little bit of play with the pipes, the least I have is 1/2" of height. I'm thinking either I get away with it, or call a plumber, but I guess it depends on the laminate + underlayment thickness and whether I add another layer of plywood or not.


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## Gary

I used 1/2" plywood on a floor like that to install ceramic tile. Had the same issue with not wanting a miss matched floor height to the next room. I glued the plywood to the original floor (Liquid nails if I remember right) & then screwed it down 6" on center both directions, making sure the screw heads were countersunk. That was a lot of screws, but 19 years later the tile floor is still in great shape. I would think if it worked for ceramic tile (not much give there),  it would work for laminate.


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## beachguy005

An issue with those old wood floors is cupping and crowning of the boards.  While you could put down a layer of plywood to make it smooth it doesn't necessarily result in flat.   
You can't get away with too much when using laminate because of the tight joints between planks.


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## nealtw

soandso said:


> Yes I've thought of that. I have a little bit of play with the pipes, the least I have is 1/2" of height. I'm thinking either I get away with it, or call a plumber, but I guess it depends on the laminate + underlayment thickness and whether I add another layer of plywood or not.



All the risers in the staircase want to be within a 1/4 of each other.
At first glance you would raise them all the 1" to match but that depends on what has been done to the lower floor, You could be into some figuring.


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## Rusty

Never glue down a second layer of subfloor or screw it to the joists. That will lead to a lot of problems.


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## soandso

samfloor said:


> Never glue down a second layer of subfloor or screw it to the joists. That will lead to a lot of problems.



How would you secure the second layer then? On this webpage they suggest gluing and screwing a second layer of plywood for floating floors: 

http://www.hoskinghardwood.com/Department/Hardwood-Floors/All-About-Subfloors--installing-flooring-over-various-sub-floors.aspx?dId=7&pageId=2

I've actually decided to hold off on the laminate flooring and wait until I can afford a better option. In the meantime I'm thinking of putting down a layer of 3/8 plywood and finishing it. I've seen some nice examples of finished plywood floors and really like it. I'm thinking if I ever do a floating floor in the future, I can install right over it.

I'm still kind of unsure what to do at the landing. I read one suggestion somewhere of leaving an area at the landing at the original height, then a reducer transition molding up to the new floor height.


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## nealtw

Dealing with the stairs is to not have a tripping hazard, adding a transition anywhere near the top of the stairs is just trading one for another.
If I was raising your floor let's say 1", I would change the nose to one that matched the new floor at the right height, remove the top three treads and space them up 3/4", 1/2" and 1/4 and they are back in code. Unless the lower floor has been changed too. Some times you can just cut the nose off all of them and add new treads and nose over old.


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