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Installing a Prefinished, Engineered Hardwood Floor over Concrete

Installing a Prefinished, Engineered Hardwood Floor over Concrete


The Philadelphia Floor Store is the one-stop shop for your hardwood and sport flooring needs. Hi, my name is Joe Glavin with Philadelphia Floor. Today we’re doing an installation video for an engineered hardwood floor over concrete. We’re using Bostik SingleStep adhesive, we’re going to core drill and test the slab for relative humidity, we’re going to show you the proper way to trowel adhesive on, the actuall install, end cuts, around obstructions–– the whole job, soup to nuts, on an engineered, prefinished hardwood floor over concrete. We test the relative humidity of the slab to make sure that the adhesive we’re going to use will keep the floor in contact with the cement slab. It gives you an understanding of what’s happening inside the slab, down a certain percentage in depth, so that when that slab is covered and normal airflow across the slab has stopped, you’ve now capped it, there’s going to be a buildup underneath there of the moisture that used to migrate through. So once it’s capped, you want to know what it’s going to be. The only way we can measure that is in the slab, approximately 40 percent, depending on how the slab itself is drying. We’re going to use the Wagner Rapid RH. This one is the 4.0 model. If you’re doing an install of floor covering, period––carpet, tile, vinyl, or hardwood–– you want to know what is in the slab as far as moisture. This is a 5-inch slab. We’re going to do 40 percent of that since it’s really just drying in one direction, which is the top. That’s going to put us at two inches. So I just put a piece of tape down two inches from the bit tip, and this bit comes with the kit, as well as a vacuum nozzle, an insertion nozzle, an insertion tool, four sensors, and a reader. So we’re going to drill down. You’ve got to keep this 90 degrees, perpendicular, to the floor, and go down two inches. It’s going to get loud. This is the RH sensor. We’re just going to drive this in by hand. It should just insert straight in. This is the reading mechanism. So that unit is going to read the bottom of the sensor, and this is going to tell us what it says. 68 degrees and 73 percent relative humidity. After you’ve done the relative humidity check on the concrete slab, you want to go ahead and look at the surface of the slab and repair any cracks, seams, flash patch any new conduit pipeways that were put in–– anything that’s going to impede the flatness of the floor, you’re going to want to repair that so that the surface of the concrete is ready for glue-up and that the engineered, prefinished hardwood floor stays flat. When the floor is ready to be installed, you’ve core tested the slab relative humidity, you’ve repaired all the surface imperfections, you’re ready to install the floor and start your glue-up. You’re going to want to strike your lines, depending on the width of the floor, I would come out that far, strike your line. Make sure your rooms are square so that you get a nice, even edge when you’re finished and you’re not cutting a thin piece and putting it right by the doorway. So you want to plan out your install and then set up your lines, snap them, and start laying your floor. This is a 5/8″ engineered floor, and Bostik SingleStep calls for a 1/4″ by 1/4″ V-notch trowel. What that’s going to do is give you proper coverage on the bottom of the board, and it’s also going to give you the proper spread rate out of your tub. I can’t stress it enough: be uniform in how you’re doing it. We’re working on a wet-laid floor, so you’re seeing some blue tape that’s down, and that’s holding the floor from sliding around at all. The method that Chris is using here is creating a very even, uniform trowel, and why is that key? Well, one, it eliminates squeeze-out. It gives you the proper spread for the 4-gallon pail of adhesive, and it allows you to create a clean edge so that you can fall off, work up to that line, finish out the length of the room, and then start again with a clean glue edge. This is a moisture-cured urethane adhesive. The idea behind the name SingleStep is, you’ve got a moisture vapor barrier and a sound deadener. There’s no need for a foam layer, or what they call a glue-pad-glue. This is all one step. So, when you get to the wall and you have to make your cut, we’re going to take the tongue. We’re going to need the groove to go into the tongue here, so we’re going to flip the board and just do a rough measurement. I know that molding’s going up here, so there’s baseboard and shoe molding going in here, so we’ll have probably about 3/4″ to play with, then we won’t have to fight against the wall. We’re about to cut one of the end cuts, and this is the Kapex from Festool. It’s a great saw. You can hook up a Festool vacuum to it, variable speed, a laser light so that you can see your cut line and be right on. Great blades on here. It’s compound miter. We use it mostly for straight cuts. You can see I put the butt-end first, and then lined up the groove of the length right flush with the tongue so that I don’t have a lot of squeeze-out when I put it in. I’m just dropping it in and then moving it over. So after the floor’s installed, you’re going to want to do one final check. Go through with one of the Bostik towels and clean up any heavy residue, glue that was missed, or anything that you might be tracking around––something that was on your knee or your foot, and then, once that dries down, go ahead and take a terrycloth towel and just dry buff the floor. Just get on your hands and knees and rub it like you’re polishing it almost. That will take up any of the residue and polish the floor up. It’s really, really important that the floor manufacturer, the distributor you’re getting it from has a quality product––that it’s square, that the seams are 90 degrees, that the boards are straight, that you’re not fighting the wood, you’re just getting the wood installed. That’s the installation of a prefinished, engineered hardwood floor over a concrete slab. Thanks for watching, and my name is Joe Glavin at Philadelphia Floor.

Comments (26)

  1. Hey there…thanks a TON for this.  Going to rip contractor carpet out of my son's house and install engineered floor on slab.  I've done a lot of 3/4" on wood framed floors before – never on slaps – so I needed a "tune up" video to get me ready.  This was perfect and I thank you sincerely.

  2. Hi Joe. How do you interpret the RH measurement? Is there a generic limit or is it adhesive dependent? What do you do if the measurement exceeds the limit?
    Thanks.

  3. awesome Joe G. ! thanks you so much this was exactly what i was needing to see. i wonder also who necessary is that core hle testing for RH? how often do you test a concrete subfloor and find out the glue won't work? I'm asking bc i have a lady, single mom, in a situation and needs help (she's poor like me) and i don't have that tool and i can't afford to get one right now. would i be safe in proceeding to help her lay her floor and take the risk? i feel internal conflict. i wanna help, but i don't wanna waste her flooring and time, yet i don't want to not do it out of an unrealistic precaution.

  4. I honestly didn't have any volume for the video.. since that's engineered wood, is it considered pergo?

  5. Joe…think this method of installation will work well on the east coast of Florida (7th floor of 8 floor building…CBS construction)…everyone is telling me to float the floor. I'm not loving the idea of a floating floor.

  6. Awesome video!  Question – I'm going to be installing engineered hardwoods to my second floor home, subfloor is plywood.  Is it recommended to use glue-down or is it ok to just use a moisture barrier/underlayment?

  7. I have seen three of these types of videos. Each one says to measure the humidity in the concrete. Not one of the videos tells you what to do with the information. What's the point of telling people to measure this unless you tell them what to do with the information.

  8. most useful video of its type I've found

  9. liked the video, but there was no explanation on the course of action you would take if the humidity was high.  The explanation assumed that the humidity was in range.  What are the next steps if the humidity is high in your concrete floor? Choose a different type of adhesive, a different type of floor, etc.?? Thanks

  10. Curious to know if you've experienced concrete floors with mastic asphalt adhesive leftovers. Do you need to remove it all or can you sinply apply the Bostik over it and install the engineered wood? Thanks!

  11. holly shit did you guys make any money? That was the slowest gluer I have ever seen 😂

  12. Joe, great video. Any suggestions for a "round" room?
    Thacks.

  13. so how did you remove the rubber hamer marks?

  14. how many minutes did you let dry the glue?

  15. so what do you do after measuring humidity ? Also, how to level concrete if it needs to be ?

  16. Very good video. Thanks,

  17. what happens if there are low spots in the concrete slab? Bought new construction and I can feel areas on the flooring that do not seem to be adhered to the concrete. Was the slab incorrectly prepped?

  18. you are right on Ron, They show you how to test, but they never say what to do if moisture is high. I, would never lay real wood over concrete. If in your basement, lay laminate. If you have a living room that has concrete floors, move! these guys are fucking idiots!

  19. How about a 4-6 mill vapor barrier

  20. I want do that in India .. If you have any contact ,sand me details.

  21. No mention of variance allowance for flatness! No mention of expansion gaps at all edges! No mention of the importance of proper layout!
    That mastic is NOT a vapor BARRIER! It IS a vapor RETARDER! All things a professional installer should know!
    Sorry…D-

  22. Let’s say you have a slab that was poured with no vapor barrier under it. You check it in dry summer weather when it hasn’t rained in months, it’s good reading but doesn’t mean when the rain comes in that the humidity level won’t be to high then as the ground gets saturated the concrete will pick it up. So seems this test is in no way fool proof.

  23. I hope you can answer a question I have. I installed engineered hardwood floors with Bostik glue a few years ago, now I want to remove a couple of walls in my house. Is there a way to lace in these types of floors where the gaps will be? Thank you for your time.

  24. excellent, however, please provide direction as to what should be done once the moisture content is determined. Is there a way to DRY the slab ?

  25. 5:47…is it ok if your wood flooring doesn’t even lay into the adhesive ?
    Because I’m a little taken back by your “I can’t stress this enough sales pitch”, yet your install is like every other Sally, Dick, and Jane install ! Give it up salesman !

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