# Need flooring advice, painted concrete subfloor



## Platypus (Jan 28, 2011)

Hey guys, 

My wife and I have been in business doing construction for many many years and have built our current home from the ground up, so I hope that qualifies me for this site. 

My son has purchased a purpose built loft with concrete floor and wants to put hardwood in. The subfloor is concrete and was painted w/ an epoxy or sealer paint of some kind. I understand that it must be ground down first in order for the glue to adhere, but I'm wondering what our options are. 

The floor has a number of cracks and patches. We'd like to do the grinding ourselves, but he is very concerned with the concrete being level and having low spots. There are currently a few level issues with the floor. If we grind all the paint off the floor, do we have to patch every single hole (from nails being removed) so that the floor is without imperfections? 

He is very opposed to a floating floor as he does not want the floor to move in spots that might be low or high. We suggested that a leveler was used, is that needed?

Thanks for the help in advance, I just want to do it right the first time.


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## Groutface (Jan 20, 2011)

Platypus said:


> Hey guys,
> 
> My wife and I have been in business doing construction for many many years and have built our current home from the ground up, so I hope that qualifies me for this site.
> 
> ...


Well ,I'm just gonna give u my opinion on this one. Depending on the condition of the substrate after u are done grinding, u may have to do several steps of "patching and levelling" including some self level products"I use ardex" and some patching "again ardex feather finsh" . Best product on the market. Patching of the concrete doesn't have to be imaculate if u r only filling nail holes,maybe one coat of feather finish. The self levelling part on the other hand needs to be perfect as wood doesn't form well over dips and crowns. A good polyurethane adhesive with an engineered hardwood would be the best way to go. Kepping it flat is the key on this installation........good luck...


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## Platypus (Jan 28, 2011)

Groutface said:


> Well ,I'm just gonna give u my opinion on this one. Depending on the condition of the substrate after u are done grinding, u may have to do several steps of "patching and levelling" including some self level products"I use ardex" and some patching "again ardex feather finsh" . Best product on the market. Patching of the concrete doesn't have to be imaculate if u r only filling nail holes,maybe one coat of feather finish. The self levelling part on the other hand needs to be perfect as wood doesn't form well over dips and crowns. A good polyurethane adhesive with an engineered hardwood would be the best way to go. Kepping it flat is the key on this installation........good luck...


I think the paint is going to come off pretty easy, but I'm concerned with the current patches coming off. Once they do though, I can just use aredex to fill them? Some of the holes have paint in them, am I going to need to grind these out w/ a hand tool? Or can I just fill them with glue and call it a day? They are no larger than a silver dollar I'd guess. I know the glue will not adhere to the hole as well.


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## Groutface (Jan 20, 2011)

Platypus said:


> I think the paint is going to come off pretty easy, but I'm concerned with the current patches coming off. Once they do though, I can just use aredex to fill them? Some of the holes have paint in them, am I going to need to grind these out w/ a hand tool? Or can I just fill them with glue and call it a day? They are no larger than a silver dollar I'd guess. I know the glue will not adhere to the hole as well.


if u r talking an extreme amount of nailholes then I would try to get the paint out....can't say that its gonna make the job fail or not,its just what I would do.the feather finish product will adhere nicely to almost anything....If the old patching after u sand it down has a tapping sound when u knock it with your knuckle the get rid of everything that has a hollow sound under it when u tap.... Remember u r only as good as the surface u go over. Hope that helps


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## Platypus (Jan 28, 2011)

Groutface said:


> if u r talking an extreme amount of nailholes then I would try to get the paint out....can't say that its gonna make the job fail or not,its just what I would do.the feather finish product will adhere nicely to almost anything....If the old patching after u sand it down has a tapping sound when u knock it with your knuckle the get rid of everything that has a hollow sound under it when u tap.... Remember u r only as good as the surface u go over. Hope that helps


Thanks for the advice. 

One other question to anyone who can answer it. 

I have a contractor suggesting a method I've never heard of before for a floating locking engineered wood. He basically said to use "Engineered Rolled Roofing" NOT glued to the concrete in a certain directional pattern, and then glue the wood in the opposite pattern to the rolled roofing. 

Have any of you guys heard of this method?


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## tazmanian (Jul 22, 2010)

forgive me for putting in my two cents - however my concern is moisture coming through the concrete and into the seams of the wood veneer. so that being said i might consider filling in the holes and putting down 1/2" ply and installing the floor over that...........................but that is what my thought is:thumbsup:


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## Platypus (Jan 28, 2011)

tazmanian said:


> forgive me for putting in my two cents - however my concern is moisture coming through the concrete and into the seams of the wood veneer. so that being said i might consider filling in the holes and putting down 1/2" ply and installing the floor over that...........................but that is what my thought is:thumbsup:


That's definitely not a bad idea, however, the unit pretty much is totally flat, so any additional build up is going to create a funky step into the unit and into the bathrooms. 

At this point, I'm thinking of just grinding down the concrete, leveling anything greater than 3/16th, moister barrier 1 coat, glue, engineered wood. Am I missing anything?


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## Groutface (Jan 20, 2011)

Platypus said:


> That's definitely not a bad idea, however, the unit pretty much is totally flat, so any additional build up is going to create a funky step into the unit and into the bathrooms.
> 
> At this point, I'm thinking of just grinding down the concrete, leveling anything greater than 3/16th, moister barrier 1 coat, glue, engineered wood. Am I missing anything?


Yer lookin pretty good.......getr done!


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## RhodesHardwood (Jun 28, 2010)

I would just get a quality floating engineered floor with a thick wear layer and float it over the concrete.


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## woodenfloorshop (Oct 18, 2010)

*id go for engineered wood flooring myself..here's why*

i haven't read through the other replies yet , so apologies if i am repeating any info.

First up , you need to check with your supplier of the sealant , what glues can be used with it. It must be compatible.

Next, How un-even is the sub-floor?This will make a big difference to whether you can even install any floor before levelleing. If you do need to level it , again check with the sealant manufacturers on compatible levelling compounds. Also some levelling compounds got to much when you try to stick wood flooring on top of them. You need a really good quality onw that will be comnpatible with both your sealant and sticking a wood floor onto it.

I know you son is not keen on an engineered wood flooring , but in my experience it is a much better option which will be faster , cheaper , easier and give a better end result. A good thick one like 18-20mm will be structural enough to not bend if placed over slight unevenness , hence no bounce.. when floated. A 12 or14mm board will bend into any dips in the floor.

Recently we installed a 12mm click engineered floor onto a customers floor that was uneeven (i explained it would bounce but they took no notice of my advice). After it was down they were not happy with the bounce , so we lifter it , self levelled and refitted it and its not perect. Zero bounce...Looks and feels jsut the same as a solid wood floor.

So in short

If you can get the floor totally even go for a 12-14mm engineered. If not completely flat , gor for a 18-20mm engineered and you should have a very solid feeling floor. It will be much less hassle than sticking down and easier to correct should you see any problems. Lifting a stuck down floor is impossible without wrecking both the wood and the subfloor.


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