concrete slab prep

We have pulled up carpeting that was glued down to the concrete slab in preparation to lay an engineered hardwood floor. I'm concerned about what the acceptable state of condition the slab needs to be for a glue down of flooring. There are trace remains of the carpet glue left; not even detectable as you glide your finger over the surface. As a test I was able to scratch it off with a screwdriver without too much effort.

Can the flooring be glued to this surface or do I need to totally remove any trace of the previous flooring adhesive? If so what would be the best approach. Scraping or abrading, dry or wet and if wet, what solvent do I use? What other steps beyond this do I need to take? I've tried to read through several hundred threads in the archive and didn't notice anyone with a similar situation so any help would be much appreciated. I gotta get moving on this because the "outlaws" are coming for Christmas!

Thanks for any help.

[Jerry T]

No on the solvents.

Use a wide razor blade scraper to clean off all the glue you can.

Keep these things in mind when you prep a slab for a glue-down installation.

The slab must to be "flat" within 3/16" in a 10' radius or 1/8" in a 6' radius. Grind off or scarify any high spots first then fill in any low areas with a portland based patch, like Mapei Planipatch. Don't attempt to use a self leveler (SLC) if you are not experienced with it.

The slab must be throughly cleaned, dust or paint over spray along the walls will cause bonding problems.

A slab must be dry, so always do a moisture test. If you have any doubts there are membranes. like Bostik's MVP, that can be troweled out to form a moisture barrier before you glue.

Acclimate the flooring, don't try to bring it in and start laying the same day.

This all sounds like a huge pain in the watoozie , and it is. Just have to grin and bear it when you glue over concrete.

[Carpets Done Wright]

Jerry is right on the money.

When scraping concrete and because it is porous, your not going to get the contaminates out of the pores.

After I grind the high spots of the slab and then fill the low spots of the slab, I then flat trowel skim coat a thin layer of Ardex SD-F Feather Finish, or Mapei PlaniPatch, to encapsulate any contaminates left in the pores of the concrete.




First scrape all the contaminates down to a residue.

Here I'm scraping thick paint where they stood all the doors up in the family room to paint them, during the new construction.


<img src="http://i-boards.com/bnp/fci/images/messages/MVC-021S_7.JPG"/>





Here is a pile of trash I scraped off what looked like a fairly clean slab.


<img src="http://i-boards.com/bnp/fci/images/messages/MVC-023S_1.JPG"/>






Here I set my 10 ft. aluminum screed/straight edge on the surface of the slab. Looks like it needs some filling, or we are going to have massive hollow spots and popping and creaking. I mapped out just where it dropped off into the swimming pool.



<img src="http://i-boards.com/bnp/fci/images/messages/MVC-025S_6.JPG"/>




Continued on the next post....Only 3 pictures allowed per post.

[Carpets Done Wright]

Ok, after mapping out the low spots, I mixed up my mud, in a 5 gallon bucket. Grabbed my screed and went to work, pouring and dragging my screed.
Here is my first pulls. I have to let them set up before I can do more, as you can't drag on top of wet mud, or you will mess up what you have done.


<img src="http://i-boards.com/bnp/fci/images/messages/MVC-031S_1.JPG"/>





After the above set up I scrapped any lumps or ridges left by the screed, and feather edge the edges, swept up and vacuumed, again.
Then I finished pouring and dragging my mud to fill this massive low spot, that was like a trough across the entire room.



<img src="http://i-boards.com/bnp/fci/images/messages/MVC-034S_2.JPG"/>




Then once that set up I scraped the lumps and the ridges and feather edged, again.
Then I skimcoated the entire surface to make it FLAT and encapsulate any contaminates in the pores of the slab.


<img src="http://i-boards.com/bnp/fci/images/messages/MVC-039S_2.JPG"/>



Continued......

[Carpets Done Wright]

After letting that dry and cure for a couple of days, I was ready to pop a line and start gluing planks.



<img src="http://i-boards.com/bnp/fci/images/messages/MVC-047S_1.JPG"/>






Taping the planks in place as I work across the room, makes for a tight, gapless installation.



<img src="http://i-boards.com/bnp/fci/images/messages/MVC-048S_3.JPG"/>




When finished, wipe the floor down and look for glue smudges to wipe with mineral spirits, then put your transition moldings on and let it sit overnight. Then next morning, pull blue tape and wipe down the floor, making sure to get any glue smudges with mineral spirits, wiped off immediately.



<img src="http://i-boards.com/bnp/fci/images/messages/MVC-050S_1.JPG"/>

Thanks for the replies. Perry, thanks for the detailed response with the photos! I know that it will help not only me.

Aren't you amazed at what you find in new construction? I'm in the window treatment business and have to deal with openings that aren't level, plumb and square.

[Jerry T]

Great job Perry.

I prep slabs pretty much the same way. Some will take more work than others, just never know until you can see the whole floor.

[Doug7]

To check for level in a specific point and grind down small high spots with minimal dust get a large Cinder Block. Use it as a giant sanding block and scrap it back and forth over level-quick or any other self-leveler that got away from you.

To help seal in contaminants there is a product called Redguard that you can roller on. It is the consistency of soupy pudding. Use a short nap roller on the first pass and don't make more than two passes. The unpainted areas are your low spots. The stuff goes on pink and dries red.

You can apply thinset and levelers over the Redguard if you wish, then re-roll to check for level and reseal the floor. Redguard is essentially a vapor barrier, so it will help keep moisture from reaching the wood.

Good luck, I am going through hell trying to put in my new click together floor!

Doug

[Carpets Done Wright]

Originally Posted by Doug7

To check for level in a specific point and grind down small high spots with minimal dust get a large Cinder Block. Use it as a giant sanding block and scrap it back and forth over level-quick or any other self-leveler that got away from you.

To help seal in contaminants there is a product called Redguard that you can roller on. It is the consistency of soupy pudding. Use a short nap roller on the first pass and don't make more than two passes. The unpainted areas are your low spots. The stuff goes on pink and dries red.

You can apply thinset and levelers over the Redguard if you wish, then re-roll to check for level and reseal the floor. Redguard is essentially a vapor barrier, so it will help keep moisture from reaching the wood.

Good luck, I am going through hell trying to put in my new click together floor!

Doug

Doug, RedGard is not recommend or any warranties express for a wood floor installation. Blocking liquid moisture is not the same as blocking vapors. I have looked at many, many, many, wood floors, where the guy at Home Depot, told them to use RedGard, in the same manner, you have suggested. What a waste of time & money, only to have some real expensive firewood!!!

I suggest Mapei PlaniPatch, with Mapei WFM, moisture barrier(good to limit 25# of vapor emissions), with Mapei 990 urethane adhesive. This combination, comes with a warranty. Dougs suggestion, comes with great risk, and a high possibility of a failure.

[Mike USMC Ret]

My engineered wood plank (Bruce Springdale) floor has been installed for over a year. I glued it to the slab. I checked flatness during prep and filled low spots and did not have any problems except one area about 1 foot in diameter area. I think the glue dried before I got the flooring on it but not sure, only my thought. Anyway, I am looking at fixing it. I have been told drill tiny hole and use syringe and to inject glue under the area and place weight on it over night. What are my other options? If I do this where can I get the supply's to do it?

Another question I have is about putting wood floor on the second floor if my house. I want to either float or nail but would like to add some sound barrier/deadening the play room is right above the great room TV area and we hear our daughter dancing. Can anything be done when I take the carpet up or is this just life and I have to deal with it.

[ctomjr]

Originally Posted by Carpets Done Wright

Doug, RedGard is not recommend or any warranties express for a wood floor installation. Blocking liquid moisture is not the same as blocking vapors. I have looked at many, many, many, wood floors, where the guy at Home Depot, told them to use RedGard, in the same manner, you have suggested. What a waste of time & money, only to have some real expensive firewood!!!

I suggest Mapei PlaniPatch, with Mapei WFM, moisture barrier(good to limit 25# of vapor emissions), with Mapei 990 urethane adhesive. This combination, comes with a warranty. Dougs suggestion, comes with great risk, and a high possibility of a failure.

Where can I buy Mapei products locally? Louisville Ky

[srickard]

Mapei products are sold at Lowes, among other places.

[academyfloor]

You can apply glue to the surface, after completing these steps:

1. Remove all the pieces of carpet from the concrete use Crain 350 / 360 Pro Stripper(This will make your workload easier)

2. You need to apply MVP4, to remove any kind of moisture and protect the concrete.

3. Let it dry for at least 24 hours. Afterwards,you can apply the glue(Bostik BST) for new engineered floor(if you are not using MVP, use Bostik Best).

Thank you,

Jacob

[Carpets Done Wright]

Originally Posted by academyfloor

You can apply glue to the surface, after completing these steps:

1. Remove all the pieces of carpet from the concrete use Crain 350 / 360 Pro Stripper(This will make your workload easier)

2. You need to apply MVP4, to remove any kind of moisture and protect the concrete.

3. Let it dry for at least 24 hours. Afterwards,you can apply the glue(Bostik BST) for new engineered floor(if you are not using MVP, use Bostik Best).

Thank you,

Jacob

MVP4, from Bostik, is OK. Some batches have red rubber chunks in it that leave the surface, anything but flat. I like Mapei WFM, which is just like MVP, only a little more installer friendly. I would use BST over BEST everytime!!! BEST slumps and does not hold its ridges as well as BST.

You only need to let it cure fore 12 hours, before getting on it with the adhesive, and you have 12 days to cover it with adhesive and wood.


Or you could use Stauf 960 and kill two birds with one stone. Moisture membrane and adhesive in one application.

[gussy]

We are installing a floating, engineered locking floor. We had a pretty flat slab with a few dips but one high spot and some rough spots around a floor outlet. we hired someone to level for us and the high spot was still high. He came back, ground it down and used some more leveler (I assume, I didnt get to see him mix it) It has dried for days now and I have tried to feather out the edges but they remain 'sandy' I cannot get them smooth and solid like in the middle of the patches and fear working it too hard and starting over. Since we are not glueing and do not depend on a bond will this sandiness be a problem?

Sadly the area still is probably not as level as it should be but I think my 'pro' is tired of the project. he keeps trying to tell me how much variance we can have but I try to remind him that is over a certain distance and this spot is just within a foot of the transitioning to tile.

[Carpets Done Wright]

Sandy???


He either used a sand mix, or he mixed too much water in the mix, making it weak.

[gussy]

Didnt get to see what he used but it was the consistency of marinara sauce. When it dried, I used a brick to feather edges and the edges just got sandy, I know I could have sanded the whole thing away without much effort. i know this because I got the vacuum out to suck up the dust and the brushes were on (oops)and it took it to the original concrete floor. I know it is not how to do it but it is the most level place we have now. The vaccuum just 'sanded' it very level. (BTW hubby was very ticked off over how long it took to clean out the vacuum since I clogged it, next time shop vac.)

[Carpets Done Wright]

It should be the consistentcy of a bowl of oatmeal or cream of wheat. Not real runny.

[mrbizness1]

I am surprised to read installing wood floors directly on a slab without a vapor barrier. I had a wood floor installed on my slab 25 years ago and the installer put down a plywood subfloor first. Thats the only way he would do it. I had to remove a few blocks due to a small termite infestation and it was a job to get them off.

[Carpets Done Wright]

If the concrete test OK for moisture vapor emissions, a moisture barrier is not needed with an engineered cross-ply constructed board. Solid wood on the other hand, is a much different animal, and is suppose to be nailed or stapled down. It is also unforgiving where any moisture is concerned, unlike an engineered. With concrete, you have the ability for it to be colder than the dew point temperature. Solid can't handle it, where an engineered will, unless it is prolonged exposure to dew points.

[regehrrl]

I am in the process of purchasing an engineered hardwood floor. CCA 3ply oak 1/2" x 5" on a concrete slab(moisture tests to be done). I was quoted $220 a gallon for the manufacturer approved adhesive, with about 5 gallons needed for a 700 sq ft area, $1100 for adhesive. It seemed to me to be too much money. I've read here that a moisture cure urethane such as Bostik BEST is an option as are some Mapei products. If the moisture test comes in at an acceptable weight, say 1-1.5 lbs after 72 hours and my slab is prep'd to correct flatness and cleanliness, would you say that I could use a Bostik or Mapei adhesive instead of this 220/gallon stuff? Thanks

[flooryou]

Originally Posted by regehrrl

I am in the process of purchasing an engineered hardwood floor. CCA 3ply oak 1/2" x 5" on a concrete slab(moisture tests to be done). I was quoted $220 a gallon for the manufacturer approved adhesive, with about 5 gallons needed for a 700 sq ft area, $1100 for adhesive. It seemed to me to be too much money. I've read here that a moisture cure urethane such as Bostik BEST is an option as are some Mapei products. If the moisture test comes in at an acceptable weight, say 1-1.5 lbs after 72 hours and my slab is prep'd to correct flatness and cleanliness, would you say that I could use a Bostik or Mapei adhesive instead of this 220/gallon stuff? Thanks

Certainly a Bistiks TKO or Pro cure would be acceptable to any mfr. Both of these adhesives are superior to Bostiks best , and cheaper too. Some mfrs. will also allow the use of Taylor 2071 adhesive, which is the most installer friendly adhesive I have ever used.

[Carpets Done Wright]

Originally Posted by regehrrl

I am in the process of purchasing an engineered hardwood floor. CCA 3ply oak 1/2" x 5" on a concrete slab(moisture tests to be done). I was quoted $220 a gallon for the manufacturer approved adhesive, with about 5 gallons needed for a 700 sq ft area, $1100 for adhesive.

I bet you meant $220 for a 5-gallon pail, and you need 5, 5-gallon pails. Because for 700 sq.ft. and a spread rate of 40 sq.ft. per gallon, that would work.


I pay right @ $70 for a 4 gallon bucket of Taylor 2071, $130 for a 5 gallon pails of Mapei 990 and $161 for Bostik's BST, with BEST being $190, and that is direct from the distributor.