Replies

1. 
   Mongo_ | Mar 14, 2002 05:01am | #1

   *
   Here's what's going on:

   Floor over bedrooms (bedroom ceiling) is getting finished off with hardwood flooring. Current floor is subfloor, subfloor is 3/4 T&G CDX over TJIs. Spans are good, loads are fine. Total area about 800 sq ft.

   The initial plan was a layer of homasote over the 3/4CDX for a bit of sound deadening, with another layer of 3/4" ply underlayment (screwed through to subfloor) on top of that. The hardwood strip flooring would then be nailed off into the ply underlayment.

   I've not used homasote as an underlayment before so I visited their website. Website said to install 5/8ths or 3/4" ply underlayment over homasote, then nail flooring off on the underlayment. Good enough, as that was my plan.

   I then called their tech support to ask a few other questions, and was told that homasote can now be used as a DIRECT underlayment for hardwood strip flooring. Homasote over the subfloor, hardwood right on top of the homasote. Nail right through it and into the subfloor. No need for the additional layer of 5/8ths or 3/4" underlayment over the homasote. It's new data, and the website is being totally rebuilt, the new site will reflect these changes.

   Made me think...

   So I hung up and called their tech support again, this time speaking to a different person. Got the same info...homasote is good as a direct underlayment for nailed strip hardwood. No good for gluedowns, just nails. I asked for, and they're sending me the new info in writing.

   I then called the flooring manufacturer. Their comments? If homasote says it's okay, then it's okay by them.

   So...

   Whaddaya guys/gals think? I don't have a whole lot of experience with homasote as an underlayment, in compression. My biggest concern to the reps was that the homasote may slightly compress over time and force the nails through the tongue of the strip flooring. They said "no worry, it ain't gonna happen."

   I just don't have enough experience with homasote to give me a warm fuzzy. I'm not terribly concerned with the manufacturer's warranty's/guarantees and them fixing a broken job down the road. I simply don't want the floor to fail so I'm leaning toward the extra ply underlayment.

   Anyone out there have any ideas about homasote as a DIRECT underlayment under strip hardwood? If it matters, the flooring is 3.5" wide by 72" long, 5/8ths" thick. Since there are no shorts it'll be more stable, so to speak.

   Still...

   Donkeyshane

   Mongo

1. 
   Bryan_Klakamp | Mar 14, 2002 05:50am | #2

   *Mongo,I saw homasote used for the first time a few months ago as an underlayment for carpeting. It was used on the first floor of a ranch with a basement. I was surprised to see it used in this way. The house was built in the 60's, and as far as I can tell, there has been no deterioration of the homasote for all those years. And I know that the homeowner, who has lived there for over 30 years, has had the carpet replaced at least once. I would not see why you couldn't use it for hardwood flooring, as long as you used long enough nails.

1. 
   CaseyR_ | Mar 14, 2002 05:57am | #3

   *The bathroom in my 1957 SF Bay Area house has some type of 1/2" fiberboard as the underlay for vinyl flooring. Homasote panels were used for the roof and the bathroom fiberboard had some type of smooth finish, so I am guessing it is from Homasote. Most of the floor held up well - no dents or warping. However, around the leaking toilet, the fiberboard was fairly badly deteriorated and there was a slight bit of deterioration where the mop water penetrated at the door where the vinyl ended. Thus I would guess that the Homasote would work well as long as it wasn't subject to moisture.Just because the underlay is outside the bathroom doesn't mean that it won't be subject to moisture, however. The living room is wall-to-wall carpet over 2" by 3/8" oak strip flooring over 2x8 subfloor. A small section of strip flooring was badly warped so I had to pull up the carpet and replace it. The 2x8 subfloor was sound but the area reeked of dog pee. I am guessing that one of the renters had a puppy that decided to relieve itself over a period of time at that spot. The 2x8s held up well, but I doubt that fiberboard would have.

1. 
   calvin_ | Mar 14, 2002 06:20am | #4

   *Mongo, as Bryan mentioned ok under carpet. Put some down over concrete and it has performed well. Remember to leave the required spacing between the panels whether underlayed over or not. I take it the added height of all this isn't a problem? You mentioned it as being upstairs. What does that do to the last riser height?

1. 
   Mongo_ | Mar 14, 2002 08:54am | #5

   *Thanks to all for your replies.I understand that it's quite common under carpet. My biggest concern is if it's firm enough to prevent the nailed hardwood flooring from moving vertically. I'm worried that if the wood moves, the nail heads may work their way up and out of the tongue, possibly splitting the groove ot resulting in a noisy/squeaky/spongy floor. Calvin, excellent point, but in this case floor height is no problem whatsoever. It was originally planned with the ply underlayment, so losing it actually makes the floor assembly thinner.The current stairs are "construction-grade" stairs/stringers w ply treads. Once the flooring is in, the current stairs/stingers will be pulled and replaced. The rise/run for the future finished stairs was computed with the extra 3/4" ply included in the flooring sandwich, so omitting it will actually improve the rise a bit.This stuff is definitely allergic to water.

2. 
   calvin_ | Mar 14, 2002 01:16pm | #6

   *Mongo, you got a scrap of homasote and some of that flooring? You could mock up a section and abuse it. Should show deflection, crushing, all that stuff you are concerned with. Close to the edge you should be able to veiw the results. Best of luck.

3. 
   Schelling_McKinley | Mar 14, 2002 01:38pm | #7

   *Mongo- Like you, I am always reluctant to experiment with something that can't be easily changed. OTOH, I have worked on a couple of houses in our area that were built in the late 50's that have fiberboard as the subfloor with pine finish floors. These have lasted without noticeable problems until there is water damage or some other necessary repair. Then the homeowner discovers what their floors have been sitting on. It does make repairs a little bit more difficult and it is very easy for one to actually step right through the fiberboard but it does seem to work. Homasote, which is a lot denser and stronger product than fiberboard, should work fine as underlayment.

4. 
   Mongo_ | Mar 14, 2002 07:04pm | #8

   *Calvin, again, thanks.I'm definitely going to do a mockup. One of the reasons is to see how well the nails penetrate the subfloor after running through the homasote. I'm slightly worried about the nails coming in through the homasote at a 45 and some simply deflecting off the subfloor. It may not happen, especially with a decent-gauge flooring nail...but I wonder nonetheless.Schelling, thanks so much for the first-hand info, that's the kind of history I was hoping for...without the water damage, though. Fiberboard as the sole underlayment? Wow. I truly appereciate the feedback, thanks guys.

5. 
   calvin_ | Mar 15, 2002 04:27am | #9

   *And Mongo, you will remember to report the test and final results back here, right? Too many times we miss the ending.........and sometimes it never ends.Thanks.

6. 
   joe_d | Mar 15, 2002 06:12pm | #10

   *Most or all HW floor manufactors say particleboard isn't good enough for their underlayment. Really skeptical that homosote will actually work trouble free. Really nothing like plywood to nail HW to.Good luck Mongo.joe d

7. 
   piffin_ | Mar 16, 2002 04:10am | #11

   *Personally, I would be looking for nails or staples long enough to get a grip on the subfloor. I've seen a lot of the sandwhich type installation you describe for post and beam structures with exposed beams and board cielings of one kind or another. We use homasote as a protective layer when remodeling over good wood floors and it does take a tremendous amt of abuse. As long as it is fastened down well, I wouldn't worry about it shifting around.

8. 
   Jeff_J._Buck | Mar 16, 2002 05:49am | #12

   *here's something to keep ya awake at nite.....would the added layer of ply on top.....just be adding another wood to nail point which could lead to more squeaking down the road. Maybe with just the sub ply...and the homosote....that lessens the squeak factor? Jeff

9. 
   Schelling_McKinley | Mar 17, 2002 01:49am | #13

   *I wouldn't have believed it either but fiberboard was the sole underlayment. It had compressed slightly where it went under the bottom plates of the wall, maybe 1/8". It was in remarkably good condition though what is the point? It is hard to think of any great functional benefit.