The best wood to shim up a new floor of plywood...?

**Basic** · 28th January 2022, 01:10 PM

I am laying a new 3/4" plywood floor over an uneven wood floor, the room is going to be an office for me, where I want to roll around on a super strong, non-squeaky floor that is flat and extremely stable, that would remind me of my previous floor which was concrete with a thin carpet on it.

My plan is to cut strips of wood to make up the difference necessary to create new flat surfaces to screw the floor to, just above the existing 2x6's that the current floor is fastened to, without removing the old wood.

The floor is far more wavy than it appears, and is slanted, so in one corner it's at zero, but the second corner it's 1" lower than corner one, and at corner 3 it's almost 2.5" lower. The house has settled for the past 80 years, and won't be settling anymore (the supporting beams have been replaced to steel and concrete bases over the years) so now what's there is solid, and not going to move any more, it's just not straight/flat. I plan to continue this new plywood floor into the adjoining room, too.

So my question is this: I plan to use Liquid Nails to ensure a solid and quiet bond, but what kind of wood would be the most strong with the least amount of "give" to use as the make-up wood? Is plywood scraps the best for this, or is any kind of 2x4 or 2x6 cut into the right strips as good as anything, if I use a bonding agent like liquid nails to use along with the screws?

I don't care about overkill (I prefer it- I'm going to be rolling around on this floor 16 hours a day every day in my office chair) so if anyone has any tips, I'd appreciate your input. I'm not an experienced wood worker but did work a lot of years as a laborer before my professional career, so between that and YouTube I plan to figure it out as I go. But the types of wood and the properties and what would work the best is the type of thing only an experienced person would know... the green lines are a general idea how the strips would go, exactly above the existing support boards/beams (not sure of the term).

Thanks again.

Wood Forum Photo.jpg

**orraloon** · 29th January 2022, 03:54 PM

I would rip those boards up as they will be a problem to whatever you lay on top. Then use red or yellowtongue sheets on the joists to make a new floor.
3600 x 800mm 19mm Flooring Particleboard Yellow Tongue - Bunnings Australia

3600 x 800mm 22mm Flooring Particleboard Red Tongue Structural - Bunnings Australia

After that the floor covering of choice.
Regards
John

**China** · 29th January 2022, 04:18 PM

Also you need to pull up the old boards and determine why the floor is warped most likely needs re stumping.

**havabeer69** · 29th January 2022, 07:09 PM

i'd also recommend ripping up the floor.

you're going to need to add 17mm ply PLUS your what ever flooring so you're going to have a decent step up into that area. which will affect doors and skirting etc etc

**Beardy** · 29th January 2022, 07:43 PM

The first question to answer for yourself is are you happy to raise the existing finished floor height by the new flooring thickness plus required packing and then your carpet or whatever thickness added to that again? You may be better to remove floor to achieve a better finished floor outcome
But if you are ok with that you can use pretty much any timber strips or even plastic horseshoe packers to level up with, I have done it many times to level and skin a concrete slab
I would also use a polyurethane adhesive over liquid nails as it does not go brittle over time. To set your packers you can use a level and straight edge but a cheap laser level will be a lot easier and quicker and worth purchasing for the job

**verawood** · 30th January 2022, 08:48 AM

And, a bit off topic,

.

Welcome to the forum.

**Tonyz** · 30th January 2022, 08:52 AM

Basic comes to us aussies asking advice.

**rwbuild** · 30th January 2022, 11:14 AM

Welcome Basic, I see your in USA
Rip up the old floor boards, bolt new joists to side of existing but level and co-planer to a level datum then sheet with OSB or ply sheet flooring

**China** · 30th January 2022, 03:54 PM

Originally Posted by Tonyz

Basic comes to us aussies asking advice.

That is because we know everything

**Greg Q** · 30th January 2022, 05:00 PM

Because the load is going to be spread by the ply, almost anything will stand up to the compression loads. Not balsa, but you get the idea. The cheapest stuff your local big box has, ripped into wedges, or even long packers under the new floor.

Of course the first class approach is to rip up the old floor, insulate and pack the existing beams up to level and then install your new floor. You won’t have different flooring levels throughout the house that way.

Liquid nails, yes. Better: Loctite construction adhesive. I used 120 tubes on my house and have zero squeaks.

16 hours in that chair? Dude, get out more.

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