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Hardwood flooring questions

loudGizmo | Posted in Construction Techniques on June 28, 2012 08:49am

I’m a long-time woodworker looking for some advice on installing hardwood floors.  After exercising my Googling skills, checking several books on hardwood flooring, and searching this site, there are still a few details I’d like to clear up.  Hopefully someone here can lend a hand.

Soon I’ll be installing about 1,200 sq. feet of 3/4″ x 4″ maple hardwood into a house built in 2006, all of it above grade and with no moisture issues, NE US with air conditioning.  I plan to use rosin paper and cleats, the latter recommended by two hardwood dealers over staples.  Cleats will be 8″ apart, driven in with a standard pneumatic floor stapler/nailer.  Since I don’t like the look of base molding plus quarter round, in order to allow for a sufficient expansion gap I plan to remove the old base molding, undercut the drywall, install the flooring, and then install new 9/16″ thick baseboard molding.  (Currently, the drywall goes to the floor, and the existing molding is about 3/8″ off the floor.)

My plan is to leave a 3/4″ expansion gap along the walls parallel to the boards, probably 1/2″ on the perpendicular walls.  The base molding plus the extra space created by undercutting the drywall will easily give me 3/4″ plus some elbow room for minor errors.

Questions:

1. Does the above sound like a reasonable plan?

2. Can someone explain to me the basic idea behind the usual recommendations for expansion gaps?  I’m very familiar with wood movement from wood working (mostly cabinetry and jewelry boxes), but the standard advice re:gaps makes me think I must be missing something.  As others have noted on this site, the business of leaving a 3/4″ gap all around is overkill on the walls perpendicular to boards, so I assume that that part of the advice is flooring companies and book authors being very conservative when telling DIYers what to do.  I would guess that the same is true for the size of the gap, as I’ve seen various recommendations online from seemingly informed sources saying the gap along the parallel walls should be 3/4″, 5/8″, 1/2″, and 3/8″.  Since I can manage the full 3/4″ where it’s needed this isn’t an issue for my installation, but I think it’s confusing and the flooring industry and writers could do a somewhat better job in educating DIYers.

The basic practice of fixing the first board, what I call “board 0″, by top plus blind nailing, raises more questions.  Every guide I see says to leave the expansion gap between board 0 and the wall.  But if that board is firmly fixed in place (as everyone says it must be), why does it need a gap beyond what’s needed to accommodate its own expansion?  If the whole floor tries to expand, won’t all the movement be away from board 0?  And if that board really could move up to 3/4″, wouldn’t it cause havoc with the installation when it rips out those nails?  Similarly, I don’t see how any part of the blind-nailed floor (like a board near a parallel walls) could move anywhere near 3/4” without causing major problems.

Just to be clear: I’m NOT looking for an excuse to violate standard recommendations on this job, and I plan to be very meticulous and conservative throughout this process.  Above all else, I want it to be right both today and years from now, and that means I have to understand the details and why so much of the standard advice conflicts with itself or is puzzling to a hardwood flooring newbie, like me.  That’s why I’m turning to this forum for advice.

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  1. User avater
    hammer1 | Jun 28, 2012 11:46am | #1

    I'm an old timer. For many years standard hardwood flooring has been installed after the baseboards are in place. The hardwood is cut to fit tight to the base. Go in any older home and this is what you will see. Today, hardwood installers don't like having to cut to fit. They prefer the base to go on afterwards. Hardwood and baseboards are going to shrink when humidity levels drop. When humidity raises, the boards expand back to where they were. There isn't a need for an expansion around a room unless you are using an engineered flooring like Pergo which is an OSB or other man made base. This type of product gets glued to each other and acts as a unit. Standard hardwood acts as individual boards. Don't confuse installation instructions for engineered products with standard flooring.

    When the baseboard goes on top of the flooring, the base will often shrink and you will see a gap. Shrinking is also an issue with the flooring, expansion is almost a non issue except in unusual circumstances like floods. Fit everything nice and tight, there will be gaps between the boards when the heat goes on.

    1. loudGizmo | Jun 29, 2012 07:53am | #2

      This is why people like me are confused

      Hammer1,

      Thanks for your reply.  It's sincerely appreciated.

      But this is why so many people who are new to hardwood flooring get so frustrated and confused.  I'm about to put a lot of maple flooring into a home we'll close on in the next couple of weeks (the real estate gods willing), and I'm hearing experienced people, many with significant incentives to see my flooring job turn out right (like the hardwood mills and dealers) telling me very different things about expansin gaps.

      And I'm definitely not confusing the installation of solid hardwood flooring with that for engineered or anything else.

      At this point, I don't know what to believe.  I see credible reports from people saying that without a gap you're in big trouble, as well as some saying no gap at all is needed.

      Anyone else care to chime in?

      1. DanH | Jun 29, 2012 08:11am | #3

        A lot depends on what time of year you install it, in what climate, and how dry the flooring is before being installed.

    2. Geoffrey | Sep 02, 2012 12:54am | #9

      I don't know what you think "old time" is but here's some info.  Before there was drywall there was plaster, pre 1930 approx.

       The sq. edged base was installed 1st and used as a stop for the application of the plaster and lathing  wall finish,

       after which there was then a cap molding(profiled) applied to the base board, subsequently, when the flooring was installed they left a 1/4 " gap around from the baseboard, that gap was then covered by a "shoe molding " which has a similar but  different profile than quarter round molding (shoe molding or base is 3/4" tall but only projects off the baseboard 1/2" creating a more pleasing effect than a full quarter round profile. Look at a truly older home and you will see what I am talking about.

      ALL wood expands or contracts according to the moisture content of the air, if you have A/C you will help balance the movement because you sustain a more consistent M/C , if you have FHA heat you will tend to "dryout" the air which will cause shrinking of the flooring.So it's good to have a humidifier in those cases.

      If you install a floor over a basement use 30# roofing felt  (tar paper) instead of rosin paper,  because there is no such thing as a dry basement, they ALL get wet/damp sooner or later.

      No matter how much you fasten a wood floor to the subfloor, it moves, the key is to try to accomadate the movement or minimize the movement if possible, all wood moves, the flooring, the studs,the subfloor, etc..

      Acclimate the flooring to the home prior to installation,  open the boxes and spread the flooring out on the floor (install felt paper first) in as aclose apattern to the final install as possible , then try and keep the M/C consistent from season to season. install the floor and then put the base on top, any shrinkage of the base will be minimal, and less noticeable than a gap where the floor butts to the base.

      I prefer to use the "old fashioned "  flooring gun that you use a mallet to drive the nail (not the pnumatic version) and of course I use cleats not staples. This method helps to drive the floor boards tight together as you go. If you install in the summer, drive the boards hard and tight, then there will be less gapping in the fall/winter when the boards shrink as they dry, just the reverse for winter installation, install snug but not "driven tight ".

      Good Luck!

       Geoff

  2. lunabean1 | Jun 30, 2012 09:41am | #4

    I installed 3/4 T&G red oak

    I installed 3/4 T&G red oak last summer - 5 1/4" planks.  Undercut the drywall and left 1/2" gap on all sides, used something called Silicone Vapor Shield underneath most of it, ran out, and used rosin paper under the rest. Used a pneumatic nailer and both 2" and 1 1/2" cleats (to avoid hitting the radiant heat between joists).   Here's what happened. 

    We had torrential rains and flooding last summer (N. Central PA).  Our place wasn't affected by the floods, but the rain did cause a problem.  The basement became very, very damp, and despite the "vapor shield" the flooring sucked up a bunch of wet.  The floor didn't budge an inch, or even a fraction, at the edges of the room.  What did happen, was that the individual boards swelled, creating ridges along the tongue side of each one.

    Fortunately, we hadn't done the sanding or finishing yet.  We bought a dehumidifier for the basement and regraded around the foundation of the house. Sanding and removing the moisture issues took care of the swelling.  Over the winter, cracks did open up - which we were expecting :)  Now that it's humid again (no air conditioning), most of the gaps have closed back up.  We still need one more round of sanding and poly, so we may fill in a couple of the bigger gaps first.

    Just my own experience, but now I'm onto the bedroom floors (same material), and I will still leave a small gap, but will not go to the trouble of undercutting drywall.  Oh yeah, the rosin paper performs just as well as the silicone, but the silicone tears less easily, is white, so any markings show up nicely (like our joist lines), and is slippery, so the wood glides right across it.

    One last thing,  we have three steps that are oak, and I used 1X oak for the risers, scribing it and putting it right on the floor and steps.  I hate 1/4 round, so I just left it.  Haven't seen a gap there yet, and like the look much better.  Am hoping that when I get around to baseboard it works just as well.

    1. jimmiem | Jun 30, 2012 11:10am | #5

      Hardwood Flooring

      I've been following this post as I would like to install my own flooring.  Also, I have a lot of the same questions as the original poster.

      What did the manufacturer recommend under your red oak, i.e. roisin or the other product?  A lot of articles I have read indicate that roofing felt should be used....but I saw an article saying it may be a health hazzard.  I also want to use Red Oak and one of the manufacturers is Quartersawn.  They sell quartersawn flooring which is supposed to expand upward instead of outward.  Ever hear of it?  Also, if a unfinished floor is put down and then polyurethaned why doesn't the seasonal movement crack the poly surface?

      1. Hokuto | Sep 03, 2012 08:53am | #10

        I should probably be embarrassed

        I did my own living room floor (which is on the 2nd storey, BTW) a couple of years ago and had no problems with it to speak of. I didn't do anything fancy, used standard tar paper under, and a HF nailing gun--one of the few things they make that are actually good quality. I used a mass-manufactured brand of flooring (the ubiquitous "Bruce"), mostly because I was loading up a 20' ship container to bring to Japan and I wanted something easily available at the BORG where I was buying a lot of other stuff; well, that and the fact that it happened to be the same brand that had been installed in the rest of the house 16 years before, so I was hoping for a match in terms of size and finish/color/design. The latter, however was not to be, since they quit making the same style in the interval. Anyway, I've had no problems with expansion/contraction, squeeks, etc. (at least none due to the installation; our sagging foundation is another story, sigh), and I probably didn't leave a full 3/4" on the sides or ends. I tried to follow the advice I could find at the Bruce website and in their instructions, with attention also paid to the various YouTube and other websites available. It's not rocket science, but you do have to be able to measure and cut properly (duh!).

        You can see a short series of photographs of the process at the URL below:

        http://photobucket.com/hardwood_floor

  3. loudGizmo | Jul 01, 2012 08:12am | #6

    Thanks for the comments so far, everyone.

    I am increasingly of the opinion that the standard advice one gets from hardwood manufacturers, books, etc. ("3/4" gap all around", "first board has to be immobilized") is a decades- or century-long compilatoin of stuff that worked under various circumstances at one time or another.

    The part of all this that puzzles me the most is simply the idea that we're supposed to nail/staple down every board and then allow room for it to move up to 3/4".  I would ask people who think that's the right approach to do the following experiment: Nail a piece of 3/4" solid hardwood to plywood or OSB, and then shift the hardwood 3/4" (or 1/2" or even 1/4") laterally without ripping out the fasteners.

    This sounds to me like a tremendous opportunity for some intrepid magazine staff, like the one at FHB, say, to do a killer article on "The Myths of Hardwood Installion -- What's Right, What's Wrong, and What You Need to Know."  If I weren't in the early stage of house buying and selling, moving, and this hardwood job, I think I'd pitch it to them.  I have a long enough background in magazine writing that I've already done the equivalent of losing a finger on the table saw (and then learned from it), so to speak.

    As for my hardwood job, I plan to keep researching over the next couple of weeks and fine tune my basic plan for a quarter-round-free installation.

  4. lunabean1 | Jul 02, 2012 09:48am | #7

    If you haven't started already...

    Here are a couple things that I figured out as I went along, but none of the resources I used told me. 

    When you start your first couple rows, you'll probably be face-nailing until the pneumatic nailer can be used.  Even though the boards will have been nailed, the force of the pneumatic nailer will push the boards back a tiny bit.  This didn't matter much in a square room, but I had a couple of intersecting hallways, with a doorjamb to fit around, and needed the boards on both sides to line up.  (Probably doesn't make much sense without a picture).  Anyway, if you have a situation where you don't want your first boards to shift, put a piece of 1/2" plywood between the first board and the wall to brace it before you use the nailer.

    Any boards bowed more than 1/16" were too hard to straighten.  Better off cutting them shorter, in half or thirds, and using them at the end of a row.  What I found easiest for straightening was a flat-head screwdriver and hammer, since I usually didn't have an extra set of hands around (unless you count my three little kids).  Hammer the tip of the screwdriver into the subfloor right in front of the tongue, at a slight backward angle.  Then use your foot to pull the screwdriver back (straigtening the board), while you nail.

    I have a hand-planer, but I found it took the same amount of time, and I got better results, if I just found a board that was a perfect fit to the first one I placed in the row.  Like if the first board I placed was 5 3/16" wide - just shy of the 5 1/4" they're supposed to be - I'd find another that was the same width. 

    From an aesthetic POV, I started out being really picky about color and grain, but after a while realized that (for me) matching grain wasn't as important as color.  There still ended up being a couple spots where I'd have liked a better match, but toward the end, well... I wasn't going to order more wood!

    1. jbatt | Jul 19, 2012 06:11pm | #8

      hardwood floor over redex

      Has anyone ever installed hardwood floor over 3/4" redex.  Our house was built in 1980.  Talked to the builder and he said they used that a lot, then latter switched to plywood, and now uses osb.  can I put the hardwood floor over the redex??

      John

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