When installing hardwood floors, should I use rosin paper, roofing felt, or nothing underneath? Why?

Question

I've installed hardwood floors, over top of OSB subfloor with a layer of roofing felt in between. I copied this from the hardwood floor contractor who did a kitchen in my home once. He'd been in business for 20 years so I trusted him. I think he said it was to prevent squeaks.

Is this true?

Does roofing felt used in this way also provide a vapor barrier, and if so, why is that important under hardwood? I can understand why it would be useful on a roof. I can understand why it would be useful for housewrap. Under a floor?

I read elswhere that rosin paper was originally used to keep floors clean (protect from the dust from drywall finishing, for example), and make it easy to slide floorboards. That seems pretty minimally valuable. Do I care if my OSB gets dusty? I usually shop-vac the OSB before laying down the floorboards, so is this really a benefit? And using rosin paper to ease sliding boards during install? Really? I never noticed a problem sliding the boards. Is this because I'm really strong? (not likely). Maybe it's because I'm using OSB as a subfloor which is a pretty smooth surface? I can imagine using plywood as a subfloor, in the days before OSB, might/could cause hitches when sliding boards during installation.

Do either of these layers provide sound-deadening or anti-squeak qualities? I figured the lack of squeaks was from using a sound, level subfloor, and installing the T&G tightly.

This question gets asked a lot in various DIY or even contrator forums. The problem is, there doesn't seem to be a general convergence to a single answer.

Answer 1

OK here we go. First of all, the most common reasons for squeaky hardwood floors are age and installation over uneven subfloors, where any movement of wood on wood makes the sounds. Age becomes a factor when the subfloor ages, shrinks a bit making the nails holding the hardwood a bit loose. Adding either a layer of felt or rosin paper isolates the wood layers and helps to minimize squeaking wood to wood. A lot of the squeaking on older floors are actually the nails moving in the subfloor, so today we use threaded nails, and for the most part and that solves that problem. So in your case, it certainly can't hurt to use some paper. Good luck.

Answer 2

Generally wood flooring these days is laid on a 3/4" plywood subfloor, whereas in the 50's and 60's a subfloor was 3" by 3/4" planking. Rosin paper would block light from the basement shining through the floorboards. I personally no longer use rosin paper on wood floor installs simply because I like to use adhesives on miter cuts used for perimeter picture frames and inlays. I find no sense in gluing wood to paper.

Answer 3

Mike Holmes says he uses it for mostly to keep dust down and to make it a little easier to slide the boards. He also says it is definitly not a vapor barrier since you make hundreds nail holes through it.

Answer 4

Rosin and felt are merely air blockers. They let moisture pass through but at a slower rate. Hardwood flooring needs to expand and contract with the house. Moisture or lack of moisture is what make the wood expand and contract. The problem is when there is too much moisture. And in my opinion, the only way to prevent floor squeaks is deck screws.

Answer 5

I'm in the process of installing engineered flooring in my house. Upstairs when I started, I skipped doing the rosin in two rooms but put it in the master room. What a difference it makes in noise. Floors are being nailed down with staples and I though they wouldn't move against the sub floor at all. When walking in the rooms that don't have the paper I do hear the floor rub slightly against the sub floor but I don't hear that in the master.

Downstairs I'm in the process of laying the floor there and have rosin paper down the living room and tar paper in the kitchen. Using tar paper since there is a much greater chance of moister variations in the subfloor there and reducing that transfer to the wood floor.

One section of my house is on slab and that area is using a foam pad with vapor barrier, but the floor there is floating and not nailed.

Answer 6

If you nail the floor securely to the subfloor using helical or "threaded" nails, you shouldn't have a problem with squeaks. An underlayment under solid floors is nearly always to restrict moisture transfer, not to prevent squeaks. As auujay (and Mike Holmes) said, nothing you put a bunch of nails through will be a 100% impermeable barrier to water; the object is simply to minimize the transfer of water.

The most common material nowadays is Tyvek, also sold as TyPar; it's a polyethylene plastic mesh that is water-resistant, but breathable, so liquid water can't get in, but air (and any water vapor it carries) can, allowing the wood to "acclimate" to changes in humidity without being at risk for real water damage. The older materials, such as tar paper and roofing felt, will do a similar job, but they're generally thicker, heavier, more costly and/or break down faster.

Answer 7

Hope this helps. 40 years in floor installation and refinishing business,my father started in 1934, we used rosin paper so oak slides in easier,over splinters and nail heads. Squeaking comes from movement, nails that move in and out of their holes. we have fixed squeaks by top nailing through oak, subfloor and into beams, no movement no noise. Black paper is used for slid and vapor barrier. for example you have a job where plywood needs to be changed {underlayment} The moisture content of kiln dried oak is 7-10% the moisture level of new plywood even home depot is 15-20% . I have seen large gym floor repairs where flooring cups due to moisture transfer. Also suppose you have a situation of flooding. oak got wet so you rip it out, the subfloor got wet but you can't rip it out. the black paper does the trick the new floor does not absorb the moisture from below, so rosin is ok for dry older homes and black paper for damp ares. And thats why you hire a contractor with experience . have a good day Oakman

Answer 8

I always thought that the felt paper under floors was for water retention, and so you couldn't see any light coming from the floor below. For example I have two horror stories from living in apartments that were T&G floors without a felt paper barrier:

1. An upstairs neighbor had a nasty habit of spilling drinks on his floor. Every time there was more liquid than the floor could wick up, it would leak right through to my ceiling. Eventually there was considerable damage to the ceiling, not to mention to my valuables below. Once the ceiling fell, I could see light coming through the small cracks between each board.

2. I got an apartment that was right above the laundry room, and the only bedroom was right over the light for that room. At night when people would do their laundry, my floor turned into a planetarium. The rays of light were small, but they were enough to be a real nuisance.

Those were both buildings built a long time ago. And I will admit that felt paper sheets rolled onto a flat floor can be anything but waterproof. I'm betting that the newer materials that you are using will be plenty to prevent any light coming through from an unfinished basement, but what will happen to any liquids that get spilled on the floor above? Do you want the flooring to sit in the water or do you want any liquids to just pass through to the other areas?

Answer 9

I have laid a lot of 3/4 inch hardwood flooring. You do not need to put roofing paper under it. On one crappy sub floor the plywood had so many little slivers the board would not slide well. I did put roofing paper down, which made the installation in that case very easy. Any beginner can use paper and it's much easier to get into place. That is the only reason to use it except on an old, old plank floor.

Answer 10

I am a builder who was taught by builders and the reason I still use rosin paper is to create air space between layers of wood flooring and underlayment so if the wood ever needs to dry out that it could. It also does knock down noise of two sheets rubbing

Answer 11

In 2009 we installed hardwood flooring in 3 bedrooms, using roofing felt as instructed by the store from which we purchased the flooring. I had already become chemically sensitive from the materials we used in the building of a home we lived in previously. When I walked in the first bedroom just after my husband had laid the tar paper and smelled it, I was concerned, but we had other things going on and wanted to get the job done and out of the way, and my husband brushed me off and went ahead and laid the flooring.

I now suffer from chronic inflammation of both sinuses & other body tissue, and our youngest son has sinus issues and has even suffered from migraines. I'm convinced it's from the off-gassing of the roofing felt under the hardwood, which has shrunk some in spite of acclimatization procedures so there are 1/32 - 1/16" gaps between the boards.

So we need to either spend thousands of dollars fixing the problem or move. I don't feel good about selling the problem to someone else.

Answer 12

Funny, I was told to use roofing felt and never even questioned it. Probably because it was relatively cheap and easy to do. I think I was told it was to prevent squeaks. But thinking about it now that doesn't really make sense as floor squeaking is caused by the flooring (or subfloor) moving up and down against a nail, not by the floorboards somehow sliding across the subfloor. If anything, having a somewhat resilient layer between the boards and the subfloor would slightly increase the likelihood of a squeak developing, wouldn't it?

Answer 13

The need for paper under hardwood is a myth. I've installed for 20 years and do not use paper. There is no difference in sound. Its a piece of PAPER. Not a magic layer. If you want a silent (relatively silent) hardwood floor then screw down your subfloor, and use the glue down installation method. (Do not glue down a solid floor). Or, if you do nail it down, and it is an engineered floor, use hardwood tongue and groove flooring glue in the end joints to help minimize movement between boards. You WILL need paper or poly when installing over a garage or crawlspace (moisture barrier). I would suggest a floating floor in these situations. I believe paper was used back in the day, and the "tradition" has been carried on. It may have served a purpose back then, but with the nails and specific guns that are used today, it is not necessary.

Answer 14

It makes it easy to spot wood chips or splinters or this or that that will prevent the next piece from drawing up tight.

Answer 15

I believe tar paper under wood floor or cabinets is an old and effective preventive against termites! Our installer did this when installing our new cabinets in a condo several years ago and we have had NO bug problem since. (The old cabinets were riddled with termites, only paint holding them together!) I cannot remember whether they attached the tar to the wall and floor or to the cabinets.

Answer 16

None of the above. You should be using a pad designed for flooring; it prevents squeaks, insulates your floor and on the higher end pads, has a moisture barrier built in. The padding is more expensive but worth it. If you decide to go without, silicon paper is the minimum underlayment you want.

Answer 17

I have looked and looked on the net for answer to this question. When I pulled up an Oak prefinished floor to replace with Maple, I noticed the roofing felt was very dirty, hardened by past spills (I am assuming) and THIN!. So I thought, I don't want this under my floor and should be replaced. Then I thought one day, this seems silly to do this step. Our childhood home had hardwood floors and no felt paper. Just good craftsmanship. I laid the floor and went at it and did two rooms. Now, here is where I think the answer comes into play and why underlayment is trivial for squeaks and pops.

1. The second room is an addition added roughly 10 years ago. The other room was built originally about 25 years ago. After the floor was laid, the original build room has some squeaks to it, but the addition has ZERO. Both without felt underlayment and Maple 3/4 '' flooring.
2. The old floor had nails from OSB to joists. AFTER installation, I have the same squeaks on the floor as I had when carpet was over the floor. The addition had screws to the joists in addition to nails.
3. Also to add, the other rooms in the house that have 3/4' solid Oak have underlayment and I get the same types of cracks and squeaks in areas that aren't walked on often as I do on my new Maple floor without underlayment.

So, I believe it is about the subfloor wood in terms of creaking, not the underlayment. Also with 3/4" subfloor and 3/4" flooring, you have 1.5" of wood, not much will be heard through that unless you are some hard walkers.

P.S. Remember this is hardwood. It is and will have character.