How do I install solid hardwood floors on a concrete slab?

Discussion in 'Hardwood and Laminates Q&A' started by Seanpeezy88, Jul 31, 2018.

  1. Seanpeezy88

    Seanpeezy88 Member

    i am looking to install solid hardwood floors on a concrete slab. I’m not quite sure on everything I need to do in order to install them. Any help?
  2. Mike Antonetti

    Mike Antonetti I Support TFP Senior Member

    Priority one is moisture vapor and controlling it.
  3. Seanpeezy88

    Seanpeezy88 Member

    How do I install wood subfloor to the concrete? Does the plywood have to be 3/4 inch?
  4. Chris 45

    Chris 45 Director of P.R. on some deserted island. I Support TFP

    Why wouldn’t you consider a full spread adhesive application?
  5. Seanpeezy88

    Seanpeezy88 Member

    That’s what I’m not sure of. Would that be a better way of doing it? Would I put the adhesive over the vapor barrier?
  6. Tom Potter

    Tom Potter I Support TFP

    The adhesive is the vapor barrier.

    This is very advanced for a DIYer. But if you are willing to take it on, everyone here can assist in one way or another.
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  7. Chris 45

    Chris 45 Director of P.R. on some deserted island. I Support TFP

    What product are you looking at installing?
  8. Seanpeezy88

    Seanpeezy88 Member

    How do I start the first row? I know I glue them and make sure they have exspansion space.
  9. Mike Antonetti

    Mike Antonetti I Support TFP Senior Member

    You don’t start the first row butted up to a non straight wall.

    Still a lot to consider before you pull the trigger. I gather info over periods of time before making decisions.

    Properly to me a line would be chalked, then I fasten straight edges to the slab, glue and place and have resistance to the hardwood as it’s pushed into place. For one room I may start 2’ off the Wall, depending on layout(1/2 board width or more per side) or the middle. By the time it’s time to fill in the test removing the straightedge is no problem, because the floor is locked in place. I tape boards together casually.
  10. Seanpeezy88

    Seanpeezy88 Member

    What is fastening a straight edge mean? Can I use a level to see if the wall is straight?
  11. Mark Brown

    Mark Brown On The Surface Flooring I Support TFP

    So, here we go.

    Installing hardwood floor on concrete, glue down application. A how to guide.

    Step one: Buy some hardwood... that parts easy. (make sure the manufacturer allows full spread applications on slab )

    Step two: Presuming the concrete is bare, check the floor for flatness. Most installations require no more than 3/16 inch in a 10 for radius, for gluedown hardwood I would recommend this is strictly followed. To determine floor flatness use a 10 foot flat, straight piece of rigid metal (level, screed, bar stock) anywhere there are hollows under that piece of metal, measure and determine how low they are. Also be aware you will find high spots.

    Step 3: After determining how out of tolerance your floor is, proceed to correct it. Depressions can be filled with Portland based cementious patching compound such as, ardex feather finish, Mapei plani patch or any other product that is recommended by the adhesive manufacturer. For any high spots it would be advisable to grind them down as much as possible to eleminate the amount of patching required. If the floor is too bad to repair with this method it is advisable to use a self levelling compound to complete this task. Not advisable to John Q. homeowner.

    Step four: Determine a layout. After choosing which direction to run the floor, identify the longest straightest wall that is parallel with that direction. Measure off said wall any distance in two points at either end of the wall. Snap a chalk line, use this line to determine how parallel ( straight ) that wall is to the rest of the install. If this line is not straight to the rest of the install, adjust it so that the tolerance is split or hidden. If it is determined that wall is "straight" then measure a board width, that is the short side of the board, now measure the room, divide the room width (in inches) by the board width. The decimal number at the end is how big your last row will be. Multiply the board width by the decimal you derived and that's how big your last boars will be. Typically you don't want to end with anything under half a board, this however is sometimes impossible depending on the room so I shoot for nothing shorter than 1.5 inches. If you have to adjust your starting row to allow for this, any size you remove from the width of the starting row is "Gained" in the end row.

    Step 4:After determining your start and end row sizes, measure out from the wall you used for a lay out line the width of the starter board, add expansion gap (typically 3/8 of an inch). Snap a new line. This is your lay line. Check to make sure it is parallel with your lay out line, or to save much hassle make the layout line a derivative of your board width. If using the "starter board" (discussed below) typically you would want to "start" 3 or 4 rows out. Multiply board width by 2 and add the size of your starter row for the chalk line.

    Step 5:Boards on the floor. There are two acceptable methods for starting glue down hardwood when on concrete. "Starter Boards" are the standard. Rip lengths of 1/2" plywood ( or if you can find a straight 2x4) at about 3 or 4 inches wide by as long as you can manage. These get nailed or glued to the floor. Typically I will use one inch concrete nails to secure them to the floor however any construction type adhesive will work (Pl 400). Lay the "straight" side of the board on your chalk line as if it were the preceeding row of hardwood. When the entire row is in place you are done (unless you nailed them) seeing as the adhesive needs 24ish hours to dry. The second method (which I prefer) is to use a PAM glue gun and a hardwood specific "hot melt" thermal adhesive. If this is an option, apply the hot melt every 6 inches on the board in sparing amounts and trowel hardwood adhesive in between. Place the back edge of the board on the chalk line and hold in place until the glue sets, typically 45 seconds. Repeat this process until the whole line is complete. Continue to install....
    If starter boards are used, the next step is the same as continuing the install.

    Step 6:Installing the floor. Regardless of what method was used to start, this process is as follows. If new, it is advised to install no more than 3-4 rows at a time so the glue does not "skin over". Multiply board width by 3-4 and then chalk a line on the floor. Spread adhesive up to this line. Install boards into the adhesive with as much haste as ability will allow to achieve the beat bond (unless your adhesive specifies a flash time). Take care to make sure all boards are tight and no gaps are present. If there is gapping, painters tape (expensive GOOD blue kind) can be used to pull them together. Hardwood straps may also be utilized with caution.

    Step seven: Roll the floor every once in a while (45 min or so) on the areas you installed with an adequate 100lb roller, in both directions to make sure proper contact is made with the floor. Any hollow spots where the glue and the flooring do not make contact or where motion is noted can be weighted with bags of sand, or relatives you don't like that are willing to stay in place for up to 24 hours.

    Step 8:REPEAT STEP 7

    Step 9:drink a beer

    Step 10:Hire a professional.
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  12. Chris 45

    Chris 45 Director of P.R. on some deserted island. I Support TFP

    Darn good advice there @Mark Brown.

    Don’t forget the mineral spirits and a bag of terry cloth towels. Any adhesive that gets on the surface of the wood needs to be cleaned up immediately.
  13. Mark Brown

    Mark Brown On The Surface Flooring I Support TFP

    I could write a book. If we wanted to get into the information contained in all of our heads, we all could. Problem I have with general questions like "how" is that it's such an open ended thing. Do I need to include information like plug the saw in... or perhaps go buy one??

    This site is wonderful for people that want help, this I have seen time and time again. We all respond best I have also noticed when clients put in the ground work first.
    Last edited: Aug 1, 2018
  14. Mike Antonetti

    Mike Antonetti I Support TFP Senior Member

    I tapconned my straightedges to the slab. Guy before us nailed tackstrip.
    Current guy glued four rows then takes an hour break. The other guy that worked when we did went on many smoke breaks.
    18 volt Hammer drill with the tapcon drill and driver was easy.
  15. Incognito

    Incognito No more Mr. Nice Guy! I Support TFP Senior Member

    No. DO NOT install solid hardwood floors on a concrete slab. Instead, choose an engineered wood and use the top of the line moisture remediation systems. I recommend Bostik

    Bostic MVP - Google Search
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  16. Mark Brown

    Mark Brown On The Surface Flooring I Support TFP

    MVP would only be for an extreme condition of moisture related issues. There a multitude of products today for hardwood installation that have an integrated moisture control system in the adhesive.

    MVP does work hella well though.
  17. Mike Antonetti

    Mike Antonetti I Support TFP Senior Member

    I’ve heard the one step adhesives do not work as well in general. Mostly due to the person applying insufficient amount/coverage, possibly inflated floors contribute.

    I agree no to solid, engineered is more stable. Moisture vapor/humidity is the issue that causes cupping/crowning that’s aesthetically displeasing, the method of installation(floating,nail down, or adhesive is not the cause of those issues.
  18. Seanpeezy88

    Seanpeezy88 Member

    Looking to install 600 sq ft of 3/4 unfinished hardwood on a concrete slab

    I already have the material purchased. Just looking for the best way to install
    Last edited by a moderator: Aug 11, 2018
  19. Seanpeezy88

    Seanpeezy88 Member

    Since my initial post, I have learned a lot. I have been doing my research and the info you guys have given me is making more sense. I’m looking to start the installation within the next month or so.
    I have received a couple of quotes from installers to do them for me but this still seems like a project that I am capable of doing.
    So just to give more info. I am installing 5 inch wide 3/4 unfinished hardwood on concrete slab.
    I’m seeing that the glue method is the best option.
    Since the floors are unfinished, do I still need to wipe off glue immediately or can it be sanded off later?
  20. Seanpeezy88

    Seanpeezy88 Member

    This is some of the best advice I have ever seen. Thank you so much. A few questions.
    What is the best adhesive to use? Is a 2 in 1 type the best?
    Will the wood floor get cold in the wintertime?
    And the boards are already in a random cut so when starting my first row I assume I start with the longest boards first?

    643CC109-EE34-4503-B559-02F8E7960119.jpeg Here is a picture of the floors

    Last edited by a moderator: Aug 11, 2018

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