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New wood floor over very old?

| Posted in General Discussion on May 12, 2000 11:06am

*
I need to replace the top floor in my house, which is quite old and has some problems. I have ordered 1×4 (7/8×4 actual) walnut (native from a small mill) for the new floor. Here a description:

The original floor is 1×4 (nominal) pine, no sub floor on joists that range from (actual) 3×8 to about 4 1/2 x 8. The joists are roughly on 16″ centers but not exactly (these are hand sawn timbers). There is some sag toward the middle (due to abuse and age) but I don’t think it was ever absolutely level. The original floor is too beat to restore.

I could remove the old floor, shim the joists to level, put in a sub floor with 3/4 ply, put the walnut over that. BUT, I would prefer to find a way to leave in the old floor to avoid the demolition, because the old floor makes a pretty ceiling for the floor below, and, (philosophical point), to preserve the historical record of the building (even though it won’t be visible). I thought about shimming right on to the old pine over the joists, but then, of course, the new walnut will be flying between the joists.

Any thoughts appreciated.

Jonathan

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Replies

  1. Guest_ | May 12, 2000 12:49pm | #1

    *
    Jonathan,

    I don't see much of a problem going over the old floor. If it's beyond repair and you can live with the sag, go for it. I live in an old house with the same floors and I think that's part of the charm of an old house.

    Hopefully, the 7/8" walnut will conform to the contour of the floor OK, not knowing how much " some sag" is.

    You will need to orient the new flooring 90 degrees to the old stuff, and not parallel to it. This might create an asthetic problem, but only you can determine that. Maybe you could sheath the floor with some plywood if you wanted to run the new flooring with the old.

    Red dog

    1. Guest_ | May 12, 2000 02:46pm | #2

      *Jonathan - This is a common situation that we face in work with historic structures. One question that interests me is how old is your house? 1 x 4 pine, if relatively regular, and joists 16" o.c. do not sound that old to me - maybe 1850's onwards?Frequently, and particularly in the 18th century, the interior walls were built on top of the floor boards, with studs tenoned in, so in general it's better for the structure if you can leave them in place. Still, I would run a structural calculation based on the joist size and span to make sure that it isn't unreasonable. Are you over 16'? A sag in large floor beams is not i usually indicative of a structural problem, we see it a lot in hand hewn oak timbers - sort of a permanent 'set.' But you have regularly-spaced joists. (PS, they were mill-sawing joists in the 18th century in some areas).With exposed beams to the room below the deflection criteria can be minimal, even l/180 - just don't count on adding a ceiling (and obviously you don't).When leaving the old flooring, you can level up by adding tapered shims scribed to the floor 'belly.' If they taper to zero (likely) hardwood is best. Keep the overall build as low as possible - it wreaks havoc on baseboards, casings, doors, etc. You'll no doubt need a transitional threshold at the door, too. In the case of removing flooring, and with a ceiling below, we either attach leveling nailers alongside the old joists or, on a recent job that was 6 x 8 timbers, up to 42" o.c. (yikes) we added level micro=lams in between and level nailers alongside of the c. 1760 beams.Sounds like it will look great - Let us know how it goes. No offense to Red Dog but I wouldn't count on 7/8 walnut conforming to much of anything except a very minimal sag, unless you face screw and plug it. Also, if memory serves walnut is really tough to nail isn't it?

  2. Jonathan_Bauer | May 12, 2000 11:06pm | #3

    *
    >Jonathan - This is a common situation that we face in work with historic structures. One question that interests me is how old is your house?

    That is a controversial question. In my opinion the date of the building is not adequately documented.

    > 1 x 4 pine, if relatively regular, and joists 16" o.c. do not sound that old to me - maybe 1850's onwards?

    I was speaking to loosely; assuming that the floors are original the boards range between 3" and 4.5" or a bit wider. They seem have been a nominal 1 by originally, but it is hard to tell because the loose boards are so worn.

    The joists are not really on 16" centers; they range from 13.5" centers to over 19" centers. None are the same. Also, some of the joists are 4 by 8, some are 3 by 7, a couple are 3 by 8.

    >
    > Frequently, and particularly in the 18th century, the interior walls were built on top of the floor boards, with studs tenoned in, so in general it's

    The walls are built on top of the floor boards, but I have not opened those walls to see if they are tenoned in. It looks like there is a footer with studs nailed to the footer and the footer nailed to the top floor (lathe nailed to the studs), but there is no way to know if any of this is original and it is not completely opened.

    > timbers - sort of a permanent 'set.' But you have regularly-spaced joists. (PS, they were mill-sawing joists in the 18th century in some areas).

    Not so, I was being to casual. But everything is pretty settled. I had to support a cracked joist and recreate support where a bearing wall was removed.
    >
    > With exposed beams to the room below the deflection criteria can be minimal, even l/180 - just don't count on adding a ceiling (and obviously you
    > don't).

    No, I am cleaning them up to reveal the beauty of the wood.

    >
    > When leaving the old flooring, you can level up by adding tapered shims scribed to the floor 'belly.' If they taper to zero (likely) hardwood is best.

    I am having a lot of trouble understanding how to shim this over the pine so that the walnut gets support. Maybe the collective could point me to a good book (since for sure I can't afford a consultant or installer).

    > anything except a very minimal sag, unless you face screw and plug it. Also, if memory serves walnut is really tough to nail isn't it?

    The sag is not minimal and I am wondering if as an alternative to screwing the walnut down, if I can have it tongue and grooved, and then edge glue ("float" the floor) assuming I can level the pine.

    Thanks very much for your thoughts and anything further. Again, sorry to all for my lack of precision.

    Jonathan.

  3. Jonathan_Bauer | May 12, 2000 11:06pm | #4

    *
    I need to replace the top floor in my house, which is quite old and has some problems. I have ordered 1x4 (7/8x4 actual) walnut (native from a small mill) for the new floor. Here a description:

    The original floor is 1x4 (nominal) pine, no sub floor on joists that range from (actual) 3x8 to about 4 1/2 x 8. The joists are roughly on 16" centers but not exactly (these are hand sawn timbers). There is some sag toward the middle (due to abuse and age) but I don't think it was ever absolutely level. The original floor is too beat to restore.

    I could remove the old floor, shim the joists to level, put in a sub floor with 3/4 ply, put the walnut over that. BUT, I would prefer to find a way to leave in the old floor to avoid the demolition, because the old floor makes a pretty ceiling for the floor below, and, (philosophical point), to preserve the historical record of the building (even though it won't be visible). I thought about shimming right on to the old pine over the joists, but then, of course, the new walnut will be flying between the joists.

    Any thoughts appreciated.

    Jonathan

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