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Subfloor/hardwood flooring question

3K views 9 replies 5 participants last post by  cep89 
#1 · (Edited)
Subfloor problems. Help!

Hey guys,

I'm renovating a home I just purchased. It was built in the 50s and still has beautiful white oak hardwood throughout most of it, which sits on a crawl space foundation. There was an add on built to the house on a slab in the 70s, and it connects as seen in the first pic below. I would like to get rid of the pocket doors (see pic 2) and continue the hardwood into the add on-- I'd of course leave the header in place and reinforce it on the sides.

My problem is that the concrete is already on the same level as the hardwood. From all my research it seems that the standard plywood subfloor, which will need to be nailed into the concrete over 6 mil poly, is supposed to be 3/4" thick. On top of that, paper, and then 1/2" by 2" unfinished white oak. (This will be finished to match the recently refinished original hardwood-- I have the info of the finish used). So the total thickness of the flooring over the slab would be 3/4" + 1/2" = 1.25" higher than the original hardwood over the crawl space.

Seems like that would be a very high transition with one huge saddle over it. I also heard that a 1" transition is the maximum, dunno if this is true. Someone suggested using 1/2" subfloor, which would still make a 1" transition. In that case I'd need to find a flooring nailer, or stapler that would take nails/staples shorter than the standard 1.5" ones used for this process. Yes, the other option is to install some kind of laminate flooring over the slab, and have two very separate and defined spaces... but I'd rather not resort to that just yet.

The OTHER issue is when I started tearing out the tile and thinset off the slab I discovered residual backing from linoleum. The linoleum itself is gone,but the bottom part of it was still glued to the concrete (see pics below). In my process of removing thinset I accidentally carved out small strips of that stuff (reasons for not stripping all of it off were 1. I heard old linoleum was placed down with asbestos-- though I'm pretty sure this one is only 15 to 20 years old, 2. It's a damn tiring job!, and 3. I need to return the tool rental to home depot). So my question is, can I lay down a subfloor right over those variations, seeing as they are at most less than 1/16th" deep? Or should I patch them up with a compound? OR do I need to tear out all of it-- God, I hope not.

I appreciate any suggestions-- and as a note, no, I have never laid down floors before, but yes, I am very handy, a perfectionist and am damn good at following instructions. Fun times ahead :thumbsup:.

Thanks,
Mike
 

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#3 ·
i don't think that you can call it "SCREWED". your issue will be the transition, which you have already thought about.

the house I am in had the same issue.. they built an addition and the finished floor ended up being about an 1"-1"1/2 higher than the original building. they made the transition with a flat edge board and did not even try to make the floors blend together.

I think you are going to find that no matter what you try to do, you are going to have two distinct spaces.

the question will then become, what type of transition will be acceptable??

although not ideal, we did learn to coupe with ours.

good luck

rod
 
#5 ·
I would cut a board as wide as possible without going past the door casings (maybe 6" or so from looking at the pic) and taper it in a table saw to the proper transition height.

International Building Codes and ADA handicap accessibility codes say the largest vertical height change allowed is 1/4". These codes don't necessarily apply to residential construction (especially existing construction), but you could go by that as a guide.

So basically you could cut a board 6" wide, with 1/4" height on the low side and 1 1/4" height on the other side, for a total height change (on the sloping surface itself) of 1". You might want to use a different type of wood, possibly with a different shade of stain so that people will notice it when walking through the doorway, which will reduce chances of tripping.

That's how I would do it. My office is an old, renovated house, with slab construction and a couple of conventional foundation additions, and we have several similar transitions throughout.
 
#6 ·
Get a glue down wood, and forget about the subfloor!

Call some specialty flooring shops (meaning not your big box stores) and you'll be able to find 3/8 and/or 1/2" thick unfinished hardwood. It might not be 2" wide, but it should come in 2 1/4" which is standard, and you'll never notice a difference. It won't be cheap because it's fairly specialized, but this material does exist and can be glued down directly over the slab.

It's available in both solid as well as engineered. The solid will have a better wear layer for future sanding, but the engineered will handle moisture a bit better, and most likely be slightly less expensive. Don't go over 1/2" thick if you're using Solid. Anything thicker should not be glued down.

You'll want to use the correct glue to lay it down: A urethane adhesive that gets troweled down, and the wood gets pressed into it. Bostiks Best and Franklin 811 or 821 are your best options. If you have even the slightest worry about moisture coming up from the slab, coat it with Franklin 531 Moisture Control first. Get the vinyl backing up before anything though.

Don't mistake glue down with glue together (floating) wood. Glue down (with a trowel) will give you the same solid feel and sound as the rest of your floor. Glue together (floating) will not.

Also, I just assumed you wanted unfinished, and were going to stain/finish it to match your existing. If you want prefinished, almost all your glue down options will be engineered. One solid floor worth looking into is Bruce Natural Choice series (used to be called Natural Reflections). It comes in several colors, but the one that you most likely will want is called Desert Natural. This is a natural finished white oak. It's 5/16" thick solid, and 2 1/4" wide. It's able to be trowel glued down, and will give you an extremely small height difference (about 3/8" with the wood and glue).


EDIT: I see you're in CA. I'm not sure if Urethane adhesives exist in your state. If not, your local specialty floor store will know of the next best thing. Or call up Franklin Adhesives and see what they say.
 
#7 ·
If I am reading this right you are planning on putting a hardwood floor in an addition that is on a slab of concrete that is directly on the ground. We wanted to do this but were advised not to because of moisture that comes through the concrete. We ended up using a product called metrofloor. It is a synthetic product that looks very much like wood and comes in planks that are randomly laid with a glue. It is only about 3/8 thick and has lasted 4 years and still looks like new, and it gets a good deal of abuse from kids and dogs coming in from the beach with sand and water on their feet. As for the left over adhesive, we had to remove it all . We used a chemical adhesive remover, it was a nasty job, but it worked. If you decide that this type of floor is not you at least test the slab for moisture.
 
#8 ·
Well that's what the vapor barrier is for underneath the slab. We hope there is one and that it's adequate for the job. Pretty much ALL homes in the southern part of the country are slab on grade and there's tons of glue-down flooring installed. My parents have 3/4" engineered glue-down, and my brother and I both have 3/8" engineered glue-down on conc slabs without any problems.
 
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