Hello forum,

I've been searching the web for quite some time now, looking for the most consensus on how we should go about replacing our old flooring. I have settled on this forum as many of the threads seemed relevant and I liked the specific advice given!

Please advise on our situation (I will be taking measurements and photos tonight so as to include additional information)

We bought our first home, and it's 104 years old.
We've started remodeling the kitchen. We've ripped out every appliance, cupboard, as well as 3-5 layers of old flooring.

We're down to the original floor/subfloor that is tongue & groove planks.
This is over a basement, and when you leave the lights on in the basement, the kitchen floor lights up like the night sky from the nail holes.

I have purchased 5/16" bamboo flooring and now I'm debating how thick of a plywood I have to get?

I was pretty set on 1/2" until I read some more about possibly using 5/8" or 3/4" even if our joists are too far apart.

Once I have measured the distance of the joists
(which I think will be far given other threads/house age)

Can someone confirm if it's honestly ok to use the 1/2" plywood over the old planks?

I'm on a really tight budget, so if at all possible I want to stick to 1/2" but I don't want to redo the floors in 2 years.

 

Welcome to the forums.

How thick are the planks and in what kind of shape?

 

Before doing anything check that floor to see how flat it is.
Almost always a floor in a house that old will be at least sagging in the middle from to long a span with over spaced and under sized joist.
Which will require some work under the house.
If not that floors not going to work out.

 

The floor certainly sagged in the middle when we still had all those layers of flooring down. It's much less apparent now as the old wood looks more like a wavy ocean to me, but every time I hear about putting a jack in the basement I imagine all my freshly mudded walls cracking and buckling from shifting that weight.
I'll check the width of the planks and measure to see how much sagging we have tonight and follow up.

 

Here's what our kitchen floor looks like.
The biggest dip that we found was 5/16" around the center of the floor.
Sorry I don't own a big enough level so I just used a door frame laid out to highlight the unevenness of the floor.

 

Here's our kitchen floor from the basement.
You can see where some of the braces have shifted or even been removed for plumbing.

The joists in this area vary in spacing. Most are around 14" inside space b/w. There was one closer to the outside wall that for some reason was closer to 17" and a few were 15-16"

 

Is your flooring glue down, nail down or floating? Important to know in addition to the size, spacing and span of the current joists to see if they are over spanned to begin with. You need a stiff floor either way and it starts with a proper subfloor. Plank floors most always need a layer over before addition of additional flooring. Don't get caught up on 1/2" vs 3/4"- as that will be a minimal cost in relation to the big job.

 

Oh last but not least, confirmed 3/4" thick planks.

 

The kitchen is about 190 sq/ft. I'm hoping that the joists are close enough together (14"-17") that we can get away with 1/2" plywood. It seems like a minimal cost, but prices practically double going from 1/2" to 5/8 or thicker, and the rest of my house is in similar condition to what you see in the photos...so I have to pinch every penny


We have 5/16" bamboo flooring to put over this plywood, and we haven't decided whether we need to glue, nail, or both. I'm totally open to suggestions on that.

I basically have the old floor removed, new floor purchased, and am trying to figure out what I can get away with putting in between/how to sandwich it all together.

 

So I was doing some additional digging last night and I'm even more confused by what we need now.

Lowes for instance, offers sheathing plywood, sanded plywood, and pressure treated plywood.

Are any of these types unacceptable to use as subflooring?
From what I gather, it sounds like sanded might be the way to go, since we need the surface smooth to lay our bamboo flooring, but I have no idea if pressure treated plywood is more important?

With that said, if I got 1/2" plywood rather than 5/8" or 3/4" and my joists are about 14-17" apart, what/how much risk am I taking?

 

You don't want pressure treated - it warps as it dries.

Advantech would be the best choice (it's actually OSB, not plywood) but you are correct that in plywood, at least, you want the smoothest choice.

 

Sanded plywood refers to a finer looking finish on 1 side of the plywood, it's not used for subfloor as there is no need to pay the extra price when the plywood gets covered up anyway. I've never laid bamboo but normally you lay roofing felt over the subfloor and under the hardwood - mainly to reduce/eliminate squeaks.

 

So OSB would be OK to use in the kitchen? I had previously ruled that out.
*I also read that if I DID use OSB, it would have to be thicker to match plywood strength (1" vs 3/4" etc.) I'm a little concerned if we make this floor too thick there will be a huge transition to other rooms

Is it true that while OSB is similar in strength to plywood these days, it ultimately doesn't recover as well from water damage as plywood (remains swollen vs shrinking back down) making it ultimately inferior to plywood in a place such as the kitchen.

And I SHOULD use an underlayment b/w subfloor and bamboo?

There seems to be more than one way to do this right, I just wish I knew which way was best for our situation

 

Good afternoon Forum,

As we continue to work on the house, I have spoken to a local flooring company as well as the bamboo flooring manufacturer but I forgot to ask about this underlayment we're using.

Basically my question is what am I supposed to use to stick this 30#roofing felt/tar paper to the original planks? Glue? Or Nailgun?- this is what we're leveling out the floor with before we lay the sanded plywood down. I was thinking we should glue it, but then I read about it being stapled down instead.

----Here's the general plan after consulting a variety of sources:
Preparing subfloor:
1. Screw down existing planks with exterior coarse-threaded screws.
- Try to secure any loose boards.
-Use screws that penetrate at least one and one quarter inch into the wood joist.

2. Gently sand over the boards to remove loose left-over glue.

3. After the subflooring is screwed tightly to the joists, vacuum to remove all dust and debris.

4. Use a six-foot long straight edge and a level to find the highest spot on the floor.
-Dips or depressions in a subfloor are immediately identified using six-foot long straightedge.
-Place it at the highest spot in the floor and slowly swing it around in a 360 degree circle. The low spots will be readily visible under the straightedge (Voids of 1/8 inch can cause problems)
-Use chalk to outline any dips (A).
-Cut tar paper to shape, glue down?,
and re-measure with straight edge (B).
- Repeat A & B until the low spots are filled up within at least 1/8” of the whole floor.

5. Mark where joists run along the floor.
-Call flooring manufacturer to verify which way both subfloor and finished planks should run to both joists and original planks.

example found online:
**
"Q: We want to add solid oak flooring to several rooms in our home. The subfloor is ¾-inch tongue-and-groove plywood, which has been screwed and glued to floor joists that are 16 inches on center. Flooring contractors we've talked to say that because of the subfloor system used, we can orient the hardwood flooring parallel to the floor joists, rather than the standard method of running them perpendicular to the joists. Is that true? And would there be any advantage to gluing the tongues into the grooves (not to the subfloor) to keep the hardwood from separating during seasonal changes?

— Judy and Kurt, Gurnee, Ill

A: Pat Hunt replies: The reason for running wood flooring perpendicular to the joists in conventional construction is that it provides a stronger, stiffer floor system. But because your subfloor is beefier than conventional construction, I'm not surprised that some flooring contractors would feel comfortable running the flooring parallel to the joists.

Even so, the major flooring trade associations take a more conservative approach. According to the National Wood Flooring Association, for example, finish flooring that runs parallel with the joists should have a layer of ½-inch plywood underlayment on top of the existing subfloor (with the long dimension perpendicular to that of the first layer), or 2x6 blocking between the joists on 24-inch centers. Also, check with your flooring manufacturer; running a floor this way may void the flooring's warranty. "
**
6. Install 1/2" plywood over planks/tar paper.
7. Install (nail) 5/16 bamboo flooring on sanded plywood.

 

I don't know about bamboo but with most hardwoods 15 lb felt is normally used. It isn't glued down, staples or just laying loose is fine - the nails in the hardwood along with gravity hold it in place. Generally scraping does a good enough job of removing the adhesive, the main thing is to insure that the flooring will lay flat.

 

I'm sorry, this is going in the wrong direction. You can't level a floor with 30# felt. And 1/2" plywood is not sufficient for nail down so its time to re-think.

First, verify that the same dip you see above is duplicated as a hump by putting your straight edge on the basement ceiling. Do the same by putting your straight edge on the bottom side of the floor joists. That should also show a hump from below.

Also, sight down whatever you are using for a straight edge and make sure that that is 100% straight.

This start will verify that the floor joists are sagging and not an issue with the floor boards themselves. I know this sound petty, but lets verify what we are up against.

Also, does the floor bounce when you walk on it? How long are the floor joists? (not how far apart), and what are the dimensions of the joists (2x8, 2x10, etc).

 

"I'm sorry, this is going in the wrong direction. You can't level a floor with 30# felt. And 1/2" plywood is not sufficient for nail down so its time to re-think."

-So both flooring guy and flooring manufacturer said 1/2" is ok because we have the original planks which are 3/4" thick and so total thickness is sufficient for a subfloor. Please explain why 1/2" does not work and thickness IS required?
-Also please explain why the felt isn't ok either? We're layering it under the plywood to get the floor level, and supposedly this stuff doesn't compress over time? What alternative would you suggest if this is not an option?

"First, verify that the same dip you see above is duplicated as a hump by putting your straight edge on the basement ceiling. Do the same by putting your straight edge on the bottom side of the floor joists. That should also show a hump from below."

- The joists are hand-hewn. You can see that one of the joists has a small u-shaped dip along the way, so we are pretty sure that our uneven floor is caused by uneven joists. We can't really measure it because the joists are not super straight length-wise or from joist-to-joist

"This start will verify that the floor joists are sagging and not an issue with the floor boards themselves. I know this sound petty, but lets verify what we are up against."

-the floor boards are old and beat as up as you can see from the pictures I posted earlier. There may be some compression, but they're not water-damaged or rotted, just old and full of holes?

"Also, does the floor bounce when you walk on it? How long are the floor joists? (not how far apart), and what are the dimensions of the joists (2x8, 2x10, etc)."

- Not sure if this is sufficient as the joists span the length of the whole house and I just measured the joints within the walls that surround the kitchen/go down to basement (we have a few walls in the basement that the joists run through.
Below the kitchen the joists are 12.5' long, 7" tall, and 2" wide.

 

So you are going to just layer felt until you make up over 1/4"? Minimum standards for nail down flooring is that the subfloor be 5/8" thick for plywood and 3/4" thick for OSB. Your 1/2" will float over 5/16" of void (filled with felt) and have nothing to grab. The thicknesses are based on minimum "Meat" needed for the cleat or staple to grab onto. Also, if the floor "bounces" then you are looking for issues. First stabilize the floor, then worry about the dip. This may include addition of supports under the floor in the basement.

Once the floor is stable, identify exactly where the floor is low and address. For a dip as large as you have, I would install wire lath and float self leveling compound initially and then use something like speed finish to feather the edges out to make a smooth surface for your underlayment. It still will not change the minimums needed for underlayment thickness of 5/8" for nail down over the low areas.

 

I called the flooring manufacturer back up and very specifically described this whole conversation, and they agreed with Czizzi that we should go ahead with the 5/8" plywood, but that we should secure it right over the original planks.

Afterwards, we should use a self-leveling compound where necessary.

Finally we can staple/nail the 1" 18guage cleats req. for this flooring directly over that plywood/self-leveling compound.

I specifically asked if that was okay because the flooring folks I spoke to originally were concerned that if we used self-leveling compound we'd run the risk of the stuff cracking and the floor crunching every time we walked over it, but 2/3 sources say self-leveling compound is ok, so I guess that's what we will do.

I'll be returning that 1/2" plywood and tar paper. As for the self-leveling compound, do we have a recommendation of what I should get?

P.S. I really appreciate everyone's advice!

 

Over wood subfloors, you need to use wire lath with self leveling compound, it can be found in the cement section of the big orange box store. No real preference to brands, however make sure you follow the installation instructions for lath, primer, consistency and max thickness of the pour. Self Leveling Compound (SLC) does not mean automatic self leveling. You will have to assist it and massage it into position. Don't just pour and walk away. It may be beneficial to nail in some roofing nails to the height you want your pour. Lay your straight edge on the ground, drive in your nails until the straight edge just clears the nail head. Use the protruding nails as your height guide.

18 ga. nails are a little wimpy and 1 inch long is too small. Use a flooring nailer in conjunction with a 15ga. angle nailer. Reference this thread as it includes lots of tips and short cuts to make your floor look nice. http://www.doityourself.com/forum/so...hrow-away.html It also has reference to a handy nailing size guide.

While returning your 30# felt paper, pick up some 15# felt paper as a continuous base to go under your whole floor. This is a standard moisture/vapor barrier that goes under all wood floors.